PATENT ABSTRACT
An economic engine generates accurate cost estimates for adapting a test script for use against an evolving application. Applications often have complex graphical user interfaces for which the permutations and combinations of GUI elements give rise to an enormous field of potential commands and command sequences to be tested. Furthermore, these applications change over time, rendering prior test scripts unworkable. The economic engine generates cost reports that reliably estimate the resources and time needed to produce new test scripts and test subsequent application versions, while greatly reducing the time, cost, and resource expenditures needed to arrive at subsequent application versions.

PATENT DESCRIPTION
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is related to following applications, all filed on the same day:
     U.S. patent application Ser. No. 12/038,665, filed Feb. 27, 2008;   U.S. patent application Ser. No. 12/038,672, filed Feb. 27, 2008;   U.S. patent application Ser. No. 12/038,676, filed Feb. 27, 2008;   U.S. patent application Ser. No. 12/038,661, filed Feb. 27, 2008; and   U.S. patent application Ser. No. 12/038,658, filed Feb. 27, 2008.   

     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     This disclosure relates to analysis and generation of cost estimates for testing graphical user interface applications, and in particular relates to estimating the costs to transform a prior test script and to test new application versions. 
     2. Related Art 
     The relentless pace of advancing technology has given rise to complex computer software applications to help automate almost every aspect of day-to-day existence. Today applications exist to assist with writing novels to filing income tax returns to analyzing historical trends in baby names. One nearly ubiquitous feature of these applications is that they employ graphical user interfaces (GUIs). Another nearly ubiquitous aspect is that the GUI APplications (GAPs) require thorough testing prior to release. 
     Nevertheless, in the past it has been easier to implement the GUI to the application than to thoroughly test the GAP. For GAPs of any significant complexity, the permutations and combinations of GUI elements gives rise to an enormous field of potential commands and command sequences that could have bugs of any severity, from insignificant to critical failure. Exacerbating the problem is that application developers are under pressure to continually add new features, update the GUI, and release new versions of applications. As a result, even if a test script for a prior version of a GAP were adequate, it is rarely the case that the original test script can adequately test the subsequent revised application. 
     Manually testing large-scale enterprise GAPs is tedious, error prone, incomplete, and laborious. Nontrivial GAPs contain hundreds of GUI screens that in turn contain thousands of GUI objects. In order to automate testing of GAPs, test engineers write programs using scripting languages (e.g., JavaScript and VBScript), and these testing scripts drive GAPs through different states by mimicking users who interact with these GAPs by performing actions on their GUI objects. Often test scripts simulate users of GAPs, and their statements access and manipulate GUI objects of these GAPs. For example, the statement: 
     VbWindow(“Login”).VbEdit(“txtAgentsName”).Set “Shawn” 
     locates a window whose caption is Login and that is created by a Visual Basic-based control, then it locates a text box whose name is txtAgentsName that is a GUI object whose parent is the login window. By calling the method Set with the parameter “Shawn”, the value of the text box is set to “Shawn”. 
     Commercial tools such as Quick Test Pro (QTP), Rational Robot, and Compuware Test Partner help generate test scripts by tracking pointing of a cursor at GUI objects and performing desired actions. These tools generate scripting code that can replay captured user actions. The generated code serves as a skeleton for creating scripts to automate script testing. Test engineers add code to the generated scripts so that these scripts can replay using different input values thereby exercising the functionality of the GAP. 
     Expanding test scripts with manually written code to automate tests makes the test script more complex, difficult to understand, maintain, and evolve. Similarly, estimating the costs to expand test scripts and to perform tests using the expanded test scripts is a difficult and highly technical challenge. Although it is known in advance that the test scripts access and manipulate GUI elements, it is not clear how to detect operations at compile time that lead to runtime errors. Using API calls exported by testing platforms remains a primary mode of accessing and manipulating GUI objects of GAPs, and these API calls lead to various run-time errors in the test scripts. For example, test personnel may use platform API calls incorrectly in the test script source code thereby accessing GUI elements that test personnel did not intend to access. 
     It is difficult to check test scripts for potential flaws caused by third party API calls that lead to incorrect tests and runtime errors in the test scripts. It is also a difficult technical challenge to estimate the costs in time and resources and time to test a subsequent revised application since these test scripts should be modified to adapt to changes in the GAPs. Furthermore, there are fundamental problems with using API calls to access and manipulate GUI objects. First, the API calls take names and property values of GUI objects as string input parameter variables. The values of these input parameters are often known only at runtime, making it impossible to apply sound checking algorithms. Second, testing platforms export dozens of different API calls, and high complexity of these API calls makes it difficult for programmers to understand which API calls to use and how to combine them to access and manipulate GUI objects. These problems lead to a wide range of bugs in the test scripts, many of which are difficult to detect during the inspection of the test script source code. 
     A further problem arises because application requirement specifications include high-level concepts that describe GAPs, specifically its GUI objects. Unfortunately, tracing GUI objects of GAPs to these high-level concepts is a difficult problem because programmers poorly document these traces or do not document them at all. Accordingly, when test personnel create GAPs, they spend considerable time to understand how to use these GAPs by reading documentation and talking to subject matter experts. This crucial knowledge is often lost after test personnel are reassigned to other tasks or quit the company. 
     One of the perceived benefits of existing approaches to creating test scripts is that type checking is not required since the script code is generated directly from GUIs. For example, given certain GUI objects in a GAP, a testing tool can produce corresponding statements that navigate to these objects using API calls with string parameters that describe their properties. However, this perceived benefit in fact gives rise to difficult technical challenges due to semantic inconsistencies between the test script and the GAP. Suppose, for example, that during the maintenance phase the GUI of the GAP changed. The scripting interpreter is not aware of the change and it would run the generated script without producing any compile-time warnings. However, the resulting script either fails at run time or produces incorrect test results because its code attempts to access GUI objects that are either changed or do not exist anymore. 
     Therefore, a need exists to address the problems noted above and other previously encountered. 
     SUMMARY 
     A test script transformation analyzer with economic cost engine (“economic cost engine architecture”) generates accurate test script transformation cost reports for applications with graphical user interfaces that change over time. As the applications change, prior test scripts are rendered unworkable. The economic cost engine architecture facilitates estimating the costs to generate new test scripts and use the new test scripts to reliably test subsequent application versions, and may greatly reduce the time, cost, and resource expenditures needed to deploy subsequent application versions. The test script transformation cost reports may identify the costs to generate new test scripts and use the new test scripts to reliably test subsequent application versions. 
     The economic cost engine architecture may accept as input a GUI difference model and GUI element metadata. The GUI difference model specifies GUI element differences between a current GAP version and a subsequent GAP version. The economic cost engine architecture further includes an economic cost engine that generates a test script transformation cost report. The test script transformation cost report may include the costs to modify script entries in the current test script to obtain a transformed test script and may include the costs to test the subsequent GAP version using the transformed test script. The economic cost engine may generate the test script transformation cost report based on an abstract syntax tree representation of a current test script and the GUI difference model. The economic cost engine may generate the test script transformation cost report based on GAP change specifiers that describe various proposed changes to a current GAP version and current test script. The economic cost engine may also use the GAP change specifiers, the representation of the current test script and current GAP version to generate the test script transformation cost report. 
     In one implementation, the economic cost engine architecture provides a product and system for test script transformation cost analysis. The architecture generates a test script transformation cost report for a subsequent graphical user interface application (GAP) version arising from a current GAP version. The architecture determines the resources and time needed to produce a transformed test script and perform testing of the subsequent GAP. The economic cost engine architecture includes an economic cost engine that includes a processor, and a memory coupled to the processor. The memory of the economic cost engine includes economic cost model logic operable to receive a GAP change specifier, search an economic model repository for an applicable GUI element change cost rule, and apply the cost rule to obtain a GUI transformation cost. The economic cost engine generates the test script transformation cost report based on the GUI transformation cost. 
     The test script transformation cost report may include cost estimates to generate a transformed test script for a subsequent GAP version arising from a current GAP version and cost estimates to test the subsequent GAP using the transformed test script. The economic cost model logic receives a GUI difference model and a current test script representation for a current test script for testing the current GAP. The current test script representation includes a test script statement vector that navigates to GUI objects in the current GAP. The economic cost model logic locates, in an object repository, a GUI object entry matching the test script statement vector and locates, in the GUI difference model, a GUI element difference entry matching the GUI object entry. The GUI element difference entry may identify a specific GUI element that matches between a current GAP version and a subsequent GAP version, but that differs in character between the current GAP version and the subsequent GAP version. The economic cost model logic analyzes the GUI element difference entry to determine whether the specific GUI element has changed, and generates one or more corresponding synthetic GAP change specifiers that reflect the change. 
     The economic cost model logic locates, in an economic models repository, a GUI element change cost rule, using the received GAP change specifiers and/or synthetic GAP change specifiers. The GUI element change cost rules may include change specifier identifiers, system resource utilization identifiers, GUI change cost estimates that indicate estimated time and/or resources needed to complete a change identified by a change specifier identifier, and dependent change specifier identifiers that identify other changes that depend on the change identified by the change specifier identifier. The GUI element change cost rules may further include dependency rankings, quality rankings, complexity rankings and dependent GUI element change costs. 
     Other systems, methods, features and advantages will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. All such additional systems, methods, features and advantages are included within this description, are within the scope of the claimed subject matter, and are protected by the following claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The economic cost engine architecture may be better understood with reference to the following drawings and description. The elements in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the system. In the figures, like-referenced numerals designate corresponding parts throughout the different views. 
         FIG. 1  shows a test script transformation analyzer with economic cost engine architecture. 
         FIG. 2  shows a GUI of a current GAP version. 
         FIG. 3  shows a GUI of a subsequent GAP version. 
         FIG. 4  illustrates a current and a subsequent GAP GUI comparison. 
         FIG. 5  shows an exemplary GUI element difference entry. 
         FIG. 6  shows a current test script. 
         FIG. 7  shows a current test script representation. 
         FIG. 8  shows an example economic cost engine system. 
         FIG. 9  shows a flow diagram for retrieving the properties of a GUI object entry from an object repository (OR). 
         FIG. 10  shows a flow diagram for identifying a GUI difference entry corresponding to a GUI object entry. 
         FIG. 11  shows a transformed test script. 
         FIG. 12  shows a flow diagram for generating a synthetic GAP change specifier. 
         FIG. 13  shows a flow diagram for outputting a test script transformation cost report based on a GUI difference model. 
         FIG. 14  illustrates another GUI element difference entry. 
         FIG. 15  show another example GUI element difference entry. 
         FIG. 16  illustrates navigation paths from a source to a destination object. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a test script transformation analyzer with economic cost engine (“economic cost engine architecture”)  110 . Although detailed descriptions of the features of the economic cost engine architecture  110  will be provided further below, a brief introduction of the economic cost engine architecture  110  will first be presented. In one implementation, the economic cost engine architecture  110  receives a GUI difference model  162  that specifies GUI element differences between a current GAP version  150  and a subsequent GAP version  152 . The GUI difference model  162  may be represented as an XML schema. The GUI element difference model  162  may include current and subsequent GAP tree models corresponding to the current GAP version  150  and subsequent GAP version  152 . In one implementation, the economic cost engine  182  receives the current GAP tree model from the GUI element difference model  162 . In another implementation, the current and subsequent GAP tree models, as well as the GUI difference model  162  are implemented as relational models stored in a database. The economic cost engine architecture  110  employs an interface  190  to receive inputs and communicate with various components, including a GUI element metadata repository  138 . The GUI element metadata repository  138  may provide detailed information regarding the GUI elements represented in the GUI difference model  162 , the current GAP  150  and the subsequent GAP  152 . 
     The economic cost engine architecture  110  includes a script parser  166  that parses a current test script  164  to obtain an intermediate representation of the current test script  164 . The intermediate representation may be an abstract syntax tree (AST)  168  or other representation of the current test script  164 . In one implementation, the economic cost engine architecture  110  employs an economic cost engine  182  that analyzes the AST  168  and the GUI difference model  162 . The economic cost engine  182  may invoke object repository (OR) lookup logic  172  to search an object repository  174  and the GUI difference model  162  to locate, in the GUI difference model  162 , the GUI elements identified by the AST  168 . The economic cost engine  182  includes economic cost model logic  196  that uses the GUI elements identified by the AST  168  and GUI difference model  162  to generate synthetic GAP change specifiers  185  that are used to search an economic models  176  repository for corresponding GUI element change cost rule. In one implementation, the economic cost model logic  196  uses GAP change specifiers  184  and synthetic GAP change specifiers  185  to search an economic models  176  repository for corresponding GUI element change cost rule. The economic cost engine  182  applies each GUI element change cost rule to obtain corresponding GUI transformation costs from which a test script transformation cost report  186  is generated, discussed further below. The economic cost engine  182  may also use historical testing metrics from a performance metrics repository  198  and cost reports repository  888  to facilitate obtaining the GUI transformation costs, discussed below. 
     The economic cost engine  182  may generate test script transformation cost reports  186  based on different combinations of available information, including: 1) GAP change specifiers  184  and/or synthetic GAP change specifiers  185 ; 2) GAP change specifiers and a current test script  164 ; 3) GAP change specifiers  184 , a current test script  164  and a current GAP version  150  (e.g., a current GAP tree model); 4) a current test script  164  and a GUI difference model  162  with GUI element difference entries; and 5) GAP change specifiers  184 , a current test script  164 , and a GUI difference model  162 . Other combinations of the same or different information may also be employed. The various combinations of available information are used by the economic cost engine  182  to analyze received and/or generate synthetic GAP change specifiers  185  that are used by the economic cost model logic  196  to locate and retrieve GUI transformation costs and generate test script transformation cost reports. 
     The accuracy of the GUI transformation costs may depend in part on how narrow the variance is between the actual costs and the costs indicated by the GUI transformation costs. A large variance corresponds to a lower accuracy, while a narrow variance corresponds to a higher accuracy. In other words, the accuracy of the GUI transformation costs may correspond to the predictability and/or confidence that the actual costs will reflect the GUI transformation costs. In one implementation, the accuracy of the GUI transformation costs varies due to the granularity of the information received by the economic cost engine  182 . For example, the GUI transformation costs generated as a result of the economic cost engine  182  receiving GAP change specifiers  184 , a current test script  164 , and a GUI difference model  162  may have a higher level of accuracy than the GUI transformation costs generated based solely on GAP change specifiers  184 . The economic cost engine  182  may employ various economic models that compensate for the lack of granularity of information provided to the economic cost engine  182 , discussed in further detail below. 
     In one implementation, the economic cost engine  182  receives GAP change specifiers  184 , a current test script  164  and a current GAP version  150 , and generates a GUI difference model  162 . In other words, the economic cost engine  182  may generate the test script transformation cost report  186  based on the AST  168 , the current GAP version  150  and GAP change specifiers  184 , discussed further below, without relying on an actual subsequent GAP version  152 . For example, the economic cost engine  182  analyzes the GAP change specifiers  184  and the current GAP version  150  (e.g., a current GAP tree model received from the GUI difference model  162 ), and generates synthetic GAP change specifiers  185 . In another implementation, the economic cost engine  182  generates the test script transformation cost report  186  based on the GAP change specifiers  184 , without analyzing either the GUI difference model  162  and/or the AST  168 . The economic cost engine  182  may generate the test script transformation cost reports  186  with change guide messages retrieved from a change guide message repository  192 . The change guide messages may provide information regarding the various changes corresponding to the GAP change specifiers  184 , GUI element change cost rules and/or GUI difference entries. 
       FIG. 2  shows a GUI of a current GAP version  150 . Table 1 shows a current GAP tree model representation of the GUI of the current GAP version  150 . The current GAP tree model shown in Table 1 specifies the GUI elements and attributes of the GUI elements of the current GAP version  150 . Table 1 illustrates that the current GAP tree model supports GUI elements that include nested GUI elements. For example, StateList window  202 , shown in  FIG. 2 , corresponds to GUI Element Alias StateList at line  11  (L 11 ) of Table 1 and nested GUI elements SaveFile, Exit, SaveChange, FileOpen, listbox School, shown at lines  18 - 21  and  59  of Table 1, correspond, respectively, to Save File  204 , Close Form  206 , Save Change  208 , Open File  210  and listbox School  216  of  FIG. 2 . In one implementation, the GUI difference model  162  results from a comparison of the current GAP tree model as shown in Table 1 and a subsequent GAP tree model illustrated below in Table 3. 
     A GAP, the GUI elements of the GAP, and the values of the GUI elements may be considered state information for the GAP. The current and subsequent GAP tree models capture the states of the current and subsequent GAP versions (e.g.,  150  and  152 ), respectively. In one implementation, GAP states are identified by sequence numbers and alias, as well as other attributes. For example, line  1  of Table 1 illustrates a ‘state’ that has a SeqNumber with a value of 0. The SeqNumber represents a unique sequence number of the current GAP version. The state is given the name State — 0 — 3556. The attributes Alias and Processid represent the alias of the current GAP version  150  and the instance process identifier for the current GAP version  150 , respectively. Recall that Table 1 and Table 3 illustrate that the current and subsequent GAP tree models support GUI elements that include nested GUI elements. Although multiple GUI elements may use an identical Alias (e.g., StateList as illustrated in Table 1 at lines  2  and  11 ) the GUI elements are further distinguished by the UniqueID attribute (e.g., 0x0 and 0x12 as shown at lines  3  and  12  of Table 1). 
     
       
         
               
             
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Current GAP tree model 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 − &lt;State SeqNumber=“0” Name=“State_0_3556” Alias=“University 
               
               
                 Directory0” ProcessId=“3556”&gt; 
               
               
                  − &lt;GUIElement Alias=“StateList”&gt; 
               
               
                   &lt;UniqueID&gt;0x0&lt;/UniqueID&gt; 
               
               
                   &lt;HWND&gt;0x170a64&lt;/HWND&gt; 
               
               
                   &lt;Location x=“87” y=“66” width=“792” height=“672” /&gt; 
               
               
                   &lt;Class&gt;WindowsForms10.Window.8.app4&lt;/Class&gt; 
               
               
                   &lt;Style&gt;0x16cf0000&lt;/Style&gt; 
               
               
                   &lt;ExStyle&gt;0xc0050900&lt;/ExStyle&gt; 
               
               
                  + &lt;GUIElement Alias=“System”&gt; 
               
               
                  + &lt;GUIElement Alias=“NAMELESS”&gt; 
               
               
                 L11 − &lt;GUIElement Alias=“StateList”&gt; 
               
               
                   &lt;UniqueID&gt;0x12&lt;/UniqueID&gt; fs 
               
               
                   &lt;HWND&gt;0x170a64&lt;/HWND&gt; 
               
               
                   &lt;Location x=“117” y=“70” width=“784” height=“638” /&gt; 
               
               
                   &lt;Class&gt;WindowsForms10.Window.8.app4&lt;/Class&gt; 
               
               
                   &lt;Style&gt;0x16cf0000&lt;/Style&gt; 
               
               
                   &lt;ExStyle&gt;0xc0050900&lt;/ExStyle&gt; 
               
               
                 L18 + &lt;GUIElement Alias=“SaveFile”&gt; 
               
               
                 L19 + &lt;GUIElement Alias=“Exit”&gt; 
               
               
                 L20 + &lt;GUIElement Alias=“SaveChange”&gt; 
               
               
                 L21 + &lt;GUIElement Alias=“FileOpen”&gt; 
               
               
                   + &lt;GUIElement Alias=“Location”&gt; 
               
               
                   + &lt;GUIElement Alias=“AcademicEmph”&gt; 
               
               
                   + &lt;GUIElement Alias=“QoIScale”&gt; 
               
               
                   + &lt;GUIElement Alias=“SocialScale”&gt; 
               
               
                   + &lt;GUIElement Alias=“AcadScale”&gt; 
               
               
                   + &lt;GUIElement Alias=“EnrolledPerc”&gt; 
               
               
                   + &lt;GUIElement Alias=“AdmittancePerc”&gt; 
               
               
                   + &lt;GUIElement Alias=“NumApps”&gt; 
               
               
                   + &lt;GUIElement Alias=“FinancialAid”&gt; 
               
               
                   + &lt;GUIElement Alias=“Expense”&gt; 
               
               
                   + &lt;GUIElement Alias=“SATMath”&gt; 
               
               
                   + &lt;GUIElement Alias=“SATVerbal”&gt; 
               
               
                   + &lt;GUIElement Alias=“SFRatio”&gt; 
               
               
                   + &lt;GUIElement Alias=“MFRatio”&gt; 
               
               
                   + &lt;GUIElement Alias=“NumStudents”&gt; 
               
               
                   + &lt;GUIElement Alias=“Control”&gt; 
               
               
                   + &lt;GUIElement Alias=“State”&gt; 
               
               
                   + &lt;GUIElement Alias=“School”&gt; 
               
               
                   + &lt;GUIElement Alias=“Location”&gt; 
               
               
                   + &lt;GUIElement Alias=“Academic Emphasis”&gt; 
               
               
                   + &lt;GUIElement Alias=“Quality of Life Scale (1-5)”&gt; 
               
               
                   + &lt;GUIElement Alias=“Social Scale (1-5)”&gt; 
               
               
                   + &lt;GUIElement Alias=“Academics Scale (1-5)”&gt; 
               
               
                   + &lt;GUIElement Alias=“Enrolled %”&gt; 
               
               
                   + &lt;GUIElement Alias=“Admittance %”&gt; 
               
               
                   + &lt;GUIElement Alias=“# Applicants (1000)”&gt; 
               
               
                   + &lt;GUIElement Alias=“Financial Aid %”&gt; 
               
               
                   + &lt;GUIElement Alias=“Expenses (1000$)”&gt; 
               
               
                   + &lt;GUIElement Alias=“SAT:math”&gt; 
               
               
                   + &lt;GUIElement Alias=“Student/Faculty Ratio”&gt; 
               
               
                   + &lt;GUIElement Alias=“SAT:verbal”&gt; 
               
               
                   + &lt;GUIElement Alias=“Male/Female Ratio”&gt; 
               
               
                   + &lt;GUIElement Alias=“Number of Students (1000)”&gt; 
               
               
                   + &lt;GUIElement Alias=“Control”&gt; 
               
               
                   + &lt;GUIElement Alias=“State”&gt; 
               
               
                   + &lt;GUIElement Alias=“SelectSchoolBtn”&gt; 
               
               
                   + &lt;GUIElement Alias=“School List”&gt; 
               
               
                 L59 + &lt;GUIElement Alias=“SchoolListbox”&gt; 
               
               
                   + &lt;GUIElement Alias=“SelectStateBtn”&gt; 
               
               
                   + &lt;GUIElement Alias=“State List”&gt; 
               
               
                 L62 + &lt;GUIElement Alias=“StateListbox”&gt; 
               
               
                  &lt;/GUIElement&gt; 
               
               
                  &lt;/GUIElement&gt; 
               
               
                 &lt;/State&gt; 
               
               
                   
               
             
          
         
       
     
     The StateListBox GUI element shown in Table 1 at line  62  corresponds to the State listbox  212  shown in  FIG. 2 .  FIG. 2  shows a horizontal navigation bar  214  as a feature of the State listbox  212 . Table 2 shows some of the attributes of State listbox  212  that may be reflected in the GUI difference model  162  as a result of a comparison between the current GAP tree model and the subsequent GAP tree model shown in Table 3. 
     
       
         
               
             
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 Current GAP StateListbox GUI element schema 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 − &lt;GUIElement Alias=“StateListbox”&gt; 
               
               
                   
                  &lt;UniqueID&gt;0x407&lt;/UniqueID&gt; 
               
               
                   
                  &lt;HWND&gt;0x90b58&lt;/HWND&gt; 
               
               
                   
                  &lt;Location x=“173” y=“86” width=“368” height=“274” /&gt; 
               
               
                   
                  &lt;Class&gt;WindowsForms10.LISTBOX.app4&lt;/Class&gt; 
               
               
                   
                  &lt;Style&gt;0x56110ac1&lt;/Style&gt; 
               
               
                   
                   &lt;ExStyle&gt;0xc0000a00&lt;/ExStyle&gt; 
               
               
                   
                  − &lt;GUIElement Alias=“StateListbox”&gt; 
               
               
                   
                    &lt;UniqueID&gt;0x410&lt;/UniqueID&gt; 
               
               
                   
                    &lt;HWND&gt;0x90b58&lt;/HWND&gt; 
               
               
                   
                   &lt;Location x=“175” y=“88” width=“364” height=“253” /&gt; 
               
               
                   
                   &lt;Class&gt;WindowsForms10.LISTBOX.app4&lt;/Class&gt; 
               
               
                   
                   &lt;Style&gt;0x56110ac1&lt;/Style&gt; 
               
               
                   
                   &lt;ExStyle&gt;0xc0000a00&lt;/ExStyle&gt; 
               
               
                   
                  − &lt;Values&gt; 
               
               
                   
                   &lt;Value SeqNumber=“0”&gt;Alabama&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“1”&gt;Alaska&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“2”&gt;Arizona&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“3”&gt;Arkansas&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“4”&gt;California&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“5”&gt;Colorado&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“6”&gt;Connecticut&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“7”&gt;Delaware&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“8”&gt;District of Columbia&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“9”&gt;Florida&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“10”&gt;Georgia&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“11”&gt;Hawaii&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“12”&gt;Idaho&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“13”&gt;Illinois&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“14”&gt;Indiana&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“15”&gt;Iowa&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“16”&gt;Kansas&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“17”&gt;Kentucky&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“18”&gt;Louisiana&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“19”&gt;Maine&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“20”&gt;Maryland&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“21”&gt;Massachusetts&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“22”&gt;Michigan&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“23”&gt;Minnesota&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“24”&gt;Mississippi&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“25”&gt;Missouri&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“26”&gt;Montana&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“27”&gt;Nebraska&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“28”&gt;Nevada&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“29”&gt;New Hampshire&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“30”&gt;New Jersey&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“31”&gt;New Mexico&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“32”&gt;New York&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“33”&gt;North Carolina&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“34”&gt;North Dakota&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“35”&gt;Ohio&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“36”&gt;Oklahoma&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“37”&gt;Oregon&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“38”&gt;Pennsylvania&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“39”&gt;Rhode Island&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“40”&gt;South Carolina&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“41”&gt;South Dakota&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“42”&gt;Tennessee&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“43”&gt;Texas&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“44”&gt;Utah&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“45”&gt;Vermont&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“46”&gt;Virginia&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“47”&gt;Washington&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“48”&gt;West Virginia&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“49”&gt;Wisconsin&lt;/Value&gt; 
               
               
                   
                   &lt;Value SeqNumber=“50”&gt;Wyoming&lt;/Value&gt; 
               
               
                   
                  &lt;/Values&gt; 
               
               
                   
                   &lt;/GUIElement&gt; 
               
               
                   
                  + &lt;GUIElement Alias=“Horizontal”&gt; 
               
               
                   
                 &lt;/GUIElement&gt; 
               
               
                   
               
             
          
         
       
     
       FIG. 3  shows a GUI of a subsequent GAP version  152 . Table 3 illustrates a subsequent GAP tree model representation of the subsequent GAP version  152 . The subsequent GAP tree model shown in Table 3 includes the GUI elements and the attributes of the GUI elements. For example, the window GUI object School  302  shown in  FIG. 3  corresponds to GUI Element Alias “School” shown at line  11  (L 11 ) of Table 3 and nested GUI elements StateListBox and SchoolCombobox shown at lines  23  and  24  of Table 3 correspond, respectively, to State listbox  304  and School combobox  306  of  FIG. 3 . 
     In one implementation, the GUI difference model  162  results from a comparison between the current GAP tree model as shown in Table 1 and a subsequent GAP tree model as shown in Table 3. In another implementation, the economic cost engine  182  analyzes the current GAP tree model using GAP change specifiers  184  to determine GAP changes that may produce the subsequent GAP tree model, from which the economic cost engine  182  generates synthetic GAP change specifiers  185 . For example, prior to actually building the subsequent GAP version  152 , a programmer may identify various proposed changes to a current GAP version  150  using the GAP change specifiers  184 . The economic cost engine  182  analyzes the GAP change specifiers  184  and current GAP tree model to generate synthetic GAP change specifiers  185  that correspond to a proposed subsequent GAP tree model. In one implementation, the economic cost engine  182  includes GAP change specifier logic that generates synthetic GAP change specifiers  185  using the current GAP tree model and the received GAP change specifiers  184 . In one implementation, the economic cost engine architecture  110  generates the synthetic GAP change specifiers  185  as a result of recording various proposed changes identified by the programmer during an interactive session with the current GAP version  150 . 
     
       
         
               
             
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 Subsequent GAP tree model 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 − &lt;State SeqNumber=“0” Name=“State_0_3068” Alias=“University 
               
               
                 Directory1” ProcessId=“3068”&gt; 
               
               
                  − &lt;GUIElement Alias=“School”&gt; 
               
               
                   &lt;UniqueID&gt;0x0&lt;/UniqueID&gt; 
               
               
                   &lt;HWND&gt;0x80b8&lt;/HWND&gt; 
               
               
                  &lt;Location x=“116” y=“88” width=“915” height=“594” /&gt; 
               
               
                   &lt;Class&gt;WindowsForms10.Window.8.app.0.378734a&lt;/Class&gt; 
               
               
                   &lt;Style&gt;0x16cf0000&lt;/Style&gt; 
               
               
                   &lt;ExStyle&gt;0xc0050900&lt;/ExStyle&gt; 
               
               
                  + &lt;GUIElement Alias=“System”&gt; 
               
               
                  + &lt;GUIElement Alias=“NAMELESS”&gt; 
               
               
                 L11 − &lt;GUIElement Alias=“School”&gt; 
               
               
                    &lt;UniqueID&gt;0x12&lt;/UniqueID&gt; 
               
               
                    &lt;HWND&gt;0x80b8&lt;/HWND&gt; 
               
               
                    &lt;Location x=“146” y=“92” width=“907” height=“560” /&gt; 
               
               
                    &lt;Class&gt;WindowsForms10.Window.8.app.0.378734a&lt;/Class&gt; 
               
               
                    &lt;Style&gt;0x16cf0000&lt;/Style&gt; 
               
               
                    &lt;ExStyle&gt;0xc0050900&lt;/ExStyle&gt; 
               
               
                 L18 + &lt;GUIElement Alias=“menuStrip1”&gt; 
               
               
                   + &lt;GUIElement Alias=“States List”&gt; 
               
               
                   + &lt;GUIElement Alias=“School List”&gt; 
               
               
                   + &lt;GUIElement Alias=“SelectStateIButton”&gt; 
               
               
                   + &lt;GUIElement Alias=“SelectSchoolButton”&gt; 
               
               
                 L23 + &lt;GUIElement Alias=“StateListbox”&gt; 
               
               
                 L24 + &lt;GUIElement Alias=“SchoolCombobox”&gt; 
               
               
                   + &lt;GUIElement Alias=“School”&gt; 
               
               
                   + &lt;GUIElement Alias=“state”&gt; 
               
               
                   + &lt;GUIElement Alias=“State”&gt; 
               
               
                   + &lt;GUIElement Alias=“location”&gt; 
               
               
                   + &lt;GUIElement Alias=“Location”&gt; 
               
               
                   + &lt;GUIElement Alias=“control”&gt; 
               
               
                   + &lt;GUIElement Alias=“Control”&gt; 
               
               
                   + &lt;GUIElement Alias=“Number of Students (1000)”&gt; 
               
               
                   + &lt;GUIElement Alias=“NumStudents”&gt; 
               
               
                   + &lt;GUIElement Alias=“Male/Female Ratio”&gt; 
               
               
                   + &lt;GUIElement Alias=“GenderRatio”&gt; 
               
               
                   + &lt;GUIElement Alias=“Student/Faculty Ratio”&gt; 
               
               
                   + &lt;GUIElement Alias=“SFRatio”&gt; 
               
               
                   + &lt;GUIElement Alias=“SAT Verbal”&gt; 
               
               
                   + &lt;GUIElement Alias=“SATVerbal”&gt; 
               
               
                   + &lt;GUIElement Alias=“SAT Math”&gt; 
               
               
                   + &lt;GUIElement Alias=“SATMath”&gt; 
               
               
                   + &lt;GUIElement Alias=“Number of Applicants”&gt; 
               
               
                   + &lt;GUIElement Alias=“NumApps”&gt; 
               
               
                   + &lt;GUIElement Alias=“Percent of Admittance”&gt; 
               
               
                   + &lt;GUIElement Alias=“PercAdmit”&gt; 
               
               
                   + &lt;GUIElement Alias=“Percent Enrolled”&gt; 
               
               
                   + &lt;GUIElement Alias=“Percent Enrolled”&gt; 
               
               
                   + &lt;GUIElement Alias=“Academics (1-5)”&gt; 
               
               
                   + &lt;GUIElement Alias=“Academics”&gt; 
               
               
                   + &lt;GUIElement Alias=“Social (1-5)”&gt; 
               
               
                   + &lt;GUIElement Alias=“Social”&gt; 
               
               
                   + &lt;GUIElement Alias=“Quality of Life (1-5)”&gt; 
               
               
                   + &lt;GUIElement Alias=“QoLife”&gt; 
               
               
                   + &lt;GUIElement Alias=“Academic Emphasis”&gt; 
               
               
                   + &lt;GUIElement Alias=“AcadEmphasis”&gt; 
               
               
                   + &lt;GUIElement Alias=“Expenses”&gt; 
               
               
                   + &lt;GUIElement Alias=“Expense”&gt; 
               
               
                   + &lt;GUIElement Alias=“Financial Aid”&gt; 
               
               
                   + &lt;GUIElement Alias=“FinancialAid”&gt; 
               
               
                  &lt;/GUIElement&gt; 
               
               
                  &lt;/GUIElement&gt; 
               
               
                 &lt;/State&gt; 
               
               
                   
               
             
          
         
       
     
     The subsequent GAP menuStrip1 GUI element schema shown in Table 3 at line  18  corresponds to the WinObject GUI object ‘menu strip’  308  shown in  FIG. 3 . The subsequent GAP menuStrip1 GUI element schema shown in Table 4 illustrates the full entry at line  18  in Table 3 and indicates that the menu strip  308  includes a nested GUI element Filemenu that includes nest GUI elements OpenFile, SaveFile, SaveAs, and Exit, shown at lines  15  of Table 4, and  22 - 25 , respectively. 
     
       
         
               
             
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                 Subsequent GAP menuStrip1 GUI element schema 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 − &lt;GUIElement Alias=“menuStrip1”&gt; 
               
               
                   &lt;UniqueID&gt;0x13&lt;/UniqueID&gt; 
               
               
                  &lt;HWND&gt;0xa0e62&lt;/HWND&gt; 
               
               
                  &lt;Location x=“146” y=“92” width=“907” height=“24” /&gt; 
               
               
                  &lt;Class&gt;WindowsForms10.Window.8.app.0.378734a&lt;/Class&gt; 
               
               
                  &lt;Style&gt;0x56000000&lt;/Style&gt; 
               
               
                  &lt;ExStyle&gt;0xc0010800&lt;/ExStyle&gt; 
               
               
                   − &lt;GUIElement Alias=“menuStrip1”&gt; 
               
               
                   &lt;UniqueID&gt;0x1c&lt;/UniqueID&gt; 
               
               
                   &lt;HWND&gt;0xa0e62&lt;/HWND&gt; 
               
               
                   &lt;Location x=“146” y=“92” width=“907” height=“24” /&gt; 
               
               
                   &lt;Class&gt;WindowsForms10.Window.8.app.0.378734a&lt;/Class&gt; 
               
               
                   &lt;Style&gt;0x56000000&lt;/Style&gt; 
               
               
                   &lt;ExStyle&gt;0xc0010800&lt;/ExStyle&gt; 
               
               
                 L15 − &lt;GUIElement Alias=“FileMenu”&gt; 
               
               
                     &lt;UniqueID&gt;0x1d&lt;/UniqueID&gt; 
               
               
                     &lt;HWND&gt;0xa0e62&lt;/HWND&gt; 
               
               
                     &lt;Location x=“148” y=“98” width=“35” height=“20” /&gt; 
               
               
                     &lt;Class&gt;WindowsForms10.Window.8.app.0.378734a&lt;/Class&gt; 
               
               
                     &lt;Style&gt;0x56000000&lt;/Style&gt; 
               
               
                     &lt;ExStyle&gt;0xc0010800&lt;/ExStyle&gt; 
               
               
                 L22   + &lt;GUIElement Alias=“OpenFile”&gt; 
               
               
                 L23   + &lt;GUIElement Alias=“SaveFile”&gt; 
               
               
                 L24   + &lt;GUIElement Alias=“SaveAsFile”&gt; 
               
               
                 L25   + &lt;GUIElement Alias=“Exit”&gt; 
               
               
                   &lt;/GUIElement&gt; 
               
               
                   &lt;/GUIElement&gt; 
               
               
                  &lt;/GUIElement&gt; 
               
               
                   
               
             
          
         
       
     
       FIG. 4  illustrates a side by side view  400  of the current and subsequent GAP that helps illustrate GUI element similarities, as well as differences, between successive GAP versions. In the view  400 , there are several GUI objects that have the same desired functionality between successive GAP versions, although aspects of the GUI object may appear different between successive GAP versions. 
     For example, referring to  FIG. 4 , differences between the current GAP version  150  and subsequent GAP version  152  include the window StateList  202 , listbox State  212 , field Academic Emphasis  402 , and field Quality of Life Scale (1-5)  404  in the current GAP version  150  are respectively represented by window School  302 , listbox State  304 , field Academic Emphasis  406 , and field Quality of Life (1-5)  408  in the subsequent GAP version  152 . In another example, consider the Save File  204 , Close Form  206 , Save Change  208  and Open File  210  GUI objects implemented in the current GAP version  150  that have been implemented in the subsequent GAP version  152  as child GUI objects of the File  410 , which is a child GUI object of the menu strip  308  GUI object. 
     It can be challenging to locate differences between GUI elements of GAPs. For example, it is not readily evident that the listbox School  216  and the combobox School  306  are meant to have the same or similar functionality between successive GAP versions. As another example, the WinObject “Select School”  218  in the current GAP version  150  has been removed at location  412  from the subsequent GAP version  152 . The GUI difference model  162  includes GUI element difference entries that list characteristics of GUI elements, for those GUI elements that match between the current GAP version  150  and the subsequent GAP version  152 , but that differ in character between the current GAP version  150  and the subsequent GAP version  152 . The GUI element difference entries facilitate the economic cost engine  182  analysis to obtain GUI transformation costs and generate test script transformation cost reports, as described in more detail below. 
       FIG. 5  shows an exemplary GUI element difference entry  504 .  FIG. 5  illustrates a GUI difference model  162  obtained by comparing a current GAP tree model as shown in Table 1 and a subsequent GAP tree model as shown in Table 3. In one implementation, the GUI difference model  162  is implemented as an XML schema that specifies each GUI element difference between successive GAP versions with a corresponding GUI element difference entry. In another implementation, the GUI difference model  162  nests GUI element difference entries to indicate parent and child GUI elements, and the level at which a GUI element difference entry is nested indicates how far the corresponding GUI element is away from a parent GUI element (root) in a navigation path. 
     In one implementation, the GUI difference model  162  omits a GUI element difference entry for GUI objects that have been deleted between successive GAP versions. Each GUI element difference entry representing a GUI object that has been modified or added between successive GAP versions includes a tag ‘Version’ that has a value of, as examples, either 0 or 1. In other words, a GUI element difference entry that does not include a Version tag indicates that the GUI object has not been modified between successive GAP versions. The Version values of 0 and 1 indicate whether the children elements of the Version represent the properties of the GUI object in the current GAP version  150  or the subsequent GAP version  152 , respectively. For example, the GUI difference entry  504  shown in  FIG. 5  indicates at line  10  that the listbox StateListbox value for SeqNumber=“8” implemented in the current GAP version  150  is “District of Columbia”, while the value in the subsequent GAP version  152  is “Florida” as indicated at line  21 . In one implementation, the GUI difference entry  504  includes a ParentChildIdentifier element, shown in lines  2  and  15  of  FIG. 5 , that identifies the relationship between two GUI objects in a given GAP GUI version, so that GUI class and inheritance constraints can be validated (discussed in detail further below). 
     Referring briefly to  FIG. 14 , the GUI difference entry  1404  indicates at line  1  that the window StateList in the current GAP version  150  corresponds to the window School in the subsequent GAP version  152  indicated at line  22  by the Version value equal to 0 and 1, respectively. The StateList and School GUI objects are of the WindowsForm10.Window.8 class, as shown at lines  8  and  28 . The sub-class identifier for the StateList and School GUI object distinguish the GUI objects (e.g., app4 and app.0.0378734a, respectively). The GUI difference entry  1404  indicates that the Location element of the StateList and School windows are different, as shown at lines  7  and  27 , respectively. However, the GUI difference entry  1404  also indicates that the Style and ExStyle elements are identical, as shown at lines  9 - 10  and  29 - 30 , respectively. 
     Referring briefly to  FIG. 15 , the GUI difference entry  1504  indicates at line  3  that the listbox SchoolListbox in the current GAP version  150  corresponds to the combobox SchoolCombobox in the subsequent GAP version  152  indicated at line  13 . The GUI difference entry  1504  indicates that the Location element of the SchoolListbox and SchoolCombobox are different, as shown at lines  7  and  18 , respectively. The GUI difference entry  1504  also indicates that the Class, Style and ExStyle elements are different, as shown at lines  8 - 10  and  19 - 21 , respectively. In particular, one or more of the properties of a WindowsForms10.LISTBOX and a WindowsForms10.COMBOBOX are different, incompatible with the properties of the other class, and child GUI elements of GUI objects of these two classes may have one or more incompatible properties. 
       FIG. 6  shows a current test script  164  for the current GAP GUI. The current test script  164  includes navigation statements (e.g., L 1  and L 6 ) that navigate to GUI objects, perform read, write, or other actions (functions) on GUI objects, and the arguments of these functions. For example, line  1  of the current test script  164  navigates to a window StateList, locates ‘Open File’ identified as a child GUI object of the window StateList, and performs an action ‘Click’ on the ‘Open File’ GUI object at XY coordinates  86 ,  12 . Through the series of navigation and action statements, the current test script  164  opens a file ‘university.data’ as indicated by lines  2 - 3 . A ‘State’ is selected from the StateListbox and a SchoolListbox is activated, based on lines  4 - 6 . The current test script  164  successively selects from the SchoolListbox the schools ‘Acme University’ and ‘State University’ located in the ‘State’ by using a ‘For Next Loop’, as a result of the navigation and action statements at lines  7 - 17  based on the coordinates  67 , School_Constant in WinObject “Select School” at line  8 . The current test script  164  uses conditional branching at lines  11 - 15  to change the academic scale to ‘3’ for ‘Acme University’ and to ‘2’ for ‘State University’, and saves the individual changes as a result of line  16 . The current test script  164  saves all the changes to a new file ‘university_revise.data’ as a result of the statements at lines  18 - 20 . 
       FIG. 7  illustrates a current test script representation  700  that the script parser  166  produces as an intermediate representation of the current test script  164 . In one implementation, the economic cost engine architecture  110  implements the current test script representation as an abstract syntax tree (AST)  168 . The current test script representation  700  represents a vector (e.g., the current test script  164 ) whose elements are vectors that represent navigation statements of the current test script  164 . In other words, the current test script representation  700  represents the navigation statements as test script statement vectors that navigate to GUI objects and perform actions on those GUI objects. Table 5 illustrates a grammar the script parser  166  may use to produce the current test script representation  700 . The terminals func, action and var represent the names of platform-specific functions that navigate to GUI objects (e.g., Window, VbEdit, and WinObject), perform read, write, or other actions (functions) on GUI objects, and the arguments of these functions, respectively. 
     
       
         
               
             
               
               
             
           
               
                 TABLE 5 
               
               
                   
               
               
                 Script Parser Grammar 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 navstmt ::= func(arg) | navstmt . Navstmt | navstmt action arg 
               
               
                   
                 fullnavstmt ::= var = navstmt | navstmt action arg 
               
               
                   
                 arg ::= expr | “,” arg | 
               
               
                   
               
             
          
         
       
     
     The script parser  166  represents the test script statement vectors as an ordered sequence of nodes that contain function names and the arguments of those functions that navigate to GUI objects. The nodes of a test script statement vector include a source node and a destination. For example, the script parser  166  may represent the test script statement vector corresponding to line  1  of the current test script  164  as source node StateList  702  and a destination node ‘Open File’  704 . The nodes of a test script statement vector may also include intermediate nodes positioned between a source node and a destination node. For example, the script parser  166  may represent the test script statement vector corresponding to line  19  of the current test script  164  as source node StateList  702 , intermediate node ‘Save a Data Record’  706  and destination node ‘File name’  708 . The test script statement vector corresponding to line  19  of the current test script  164  may be further expressed as ( 702 - 706 - 708 - 720 - 722 ), including the method ‘Set’  720  and value ‘university revise.data’  722 . 
     The test script statement vectors may include looping and conditional branching nodes (e.g., loop  724  and branch  726 , respectively). In one implementation, the loop  724  node is followed by a loop variable (e.g., school_constant  730 ) for which a range of values, from a lower to an upper bound (e.g., J  732  and K  734 ), are evaluated and used in expressions within the scope of the loop  724  (e.g.,  67 , school_constant coordinates  736 ). The branch  726  may be followed by one or more conditions (e.g., condition-1  738  and condition-2  740 ). The economic cost engine  182  may use the loop  724  and branch  726  nodes, and range values and conditions (e.g., J  732 , K  734 , condition-1  738  and condition-2  740 ) to recursively evaluate the current test script representation  700 . 
     In one implementation, the GAP change specifiers  184  includes a model specifier (discussed in further detail below) that identifies the GUI element change cost rule to use to obtain a GUI transformation cost corresponding to a loop  724 . The GUI element change cost rule for a loop  724  may result in the economic cost model logic  196  obtaining a GUI transformation cost that represents a multiplier equal to the number of values in the range from a lower to an upper bound (e.g., J  732  and K  734 ) that is applied to the GUI transformation costs for the test script statements within the scope of the loop  724  (e.g., lines  8 - 16  in  FIG. 6 ). For example, the GUI transformation cost corresponding to loop  724 , based on the lower to the upper bound (e.g., J  732  and K  734 ), may equal 10 and the GUI transformation costs corresponding to the test script statements within the scope of the loop  724  (e.g., lines  8 - 16  in  FIG. 6 ) may equal  500 , resulting in a total GUI transformation cost of 5,000 for the test script statements including loop  724  (e.g., lines  7 - 17 ). In another example, the GUI transformation cost obtained by applying the GUI element change cost rule for a loop  724  may represent a single weighted valued (e.g., 50) that the economic cost model logic  196  adds to the GUI transformation costs corresponding to the test script statements within the scope of loop  724  so that the total GUI transformation cost of  550  results for the test script statements including loop  724  (e.g., lines  7 - 17 ). 
     The GUI element change cost rule for a branch  726  may result in obtaining a GUI transformation cost that is based on the number of conditions (e.g., condition-1  738  and condition-2  740 ) within the scope of the branch  726 , and the GUI transformation costs for the branch  726  and the test script statements within the scope of the branch  726  are added to obtain the total GUI transformation costs. In another implementation, the GUI transformation cost corresponding to the branch  726  is a multiplier that is applied to the GUI transformation costs corresponding to the test script statements within the scope of the branch  726 . For example, two conditions (e.g., condition-1  738  and condition-2  740 ) exist within the scope of the branch  726 , corresponding to a GUI transformation costs of  2  for the branch  726  and the GUI transformation costs of the lines within the scope of the branch  726  are  100  resulting in a total GUI transformation cost of  200  for the test script statements including branch  726  (e.g., lines  11 - 15 ). 
     The script parser  166  evaluates arguments of navigation and action functions as expressions, variables and constants. The arguments express the physical properties of GUI objects to which the test script statement vectors navigate and values used to perform actions on those GUI objects. For example, the ‘86,12’ coordinates  712  identify the location for a pointing device to perform an action ‘Click’  710  on the ‘Open File’  704  GUI object, which is a child GUI Object of the window StateList  702 . The economic cost engine  182  uses the names of the GUI objects (e.g., StateList  702  and ‘Open File’  704 ) navigated to by the test script statement vectors to locate the corresponding physical properties of the GUI objects stored in an object repository  174 , identify corresponding GUI difference entries and generate synthetic GAP change specifiers  185 . 
     In one implementation, the economic cost engine  182  uses the OR lookup logic  172  to locate, in the object repository  174 , the physical properties of the GUI objects navigated to by a test script statement vector, and locate, in the GUI difference model  162 , corresponding GUI difference entries. The economic cost engine  182  generates synthetic GAP change specifiers  185  and invokes the economic cost model logic  196  to locate corresponding GUI element change cost rules in the economic models  176  repository using GAP change specifiers  184  and synthetic GAP change specifiers  185 . In one implementation, the OR lookup logic  172  is divided into two sub-functions: 1) lookup logic adapted to locate and retrieve the physical properties of the GUI objects navigated to by the test script statement vector (e.g.,  702 - 704 ,  702 - 706 - 708 , and  702 - 714 ); and 2) locator logic that finds and returns a GUI element difference entry (node) in the GUI difference model  162  that corresponds to the GUI object with the given physical properties. The economic cost model logic  196  generates synthetic GAP change specifiers  185  that are used to locate applicable GUI element change cost rules, based on the lookup logic and locator logic results from the OR lookup logic  172 . The OR lookup logic  172  may include path traversal logic, discussed in further detail below, to identify possible navigation paths of a test script statement vector between a source node GUI object and destination node GUI object to which a test script statement vector navigates. 
     Table 6 illustrates one implementation of an object repository  174 , in the form of an XML schema. The object repository  174  includes a GUI object entry for each GUI object of the current GAP version  150  identified in the current test script  164 . The object repository  174  may be generated by a script writing tool, such as Quick Test Pro (QTP), Rational Robot, and Compuware Test Partner. The economic cost engine  182  may query the object repository  174  to identify the physical properties of the GUI objects navigated to by the test script statement vectors represented by the current test script representation  700 . Physical properties of a GUI object may indicate whether the GUI object is hidden, read-only, a number and default values, as shown in Table 7. 
     For example, the economic cost engine  182  analyzes the GUI objects  702 - 714  in the test script statement vector. The ‘19,22’ coordinate  718  identifies the location for a pointing device to perform an action ‘Click’  716  on the GUI object SchooListbox  714 , which is a child GUI Object of the window StateList  702 . The economic cost engine  182  invokes the OR lookup logic  172  to locate the physical properties of the GUI objects  702  and  714 . The OR lookup logic  172  locates the physical properties of the window StateList  702  and the WinObject SchoolListbox  714 , as shown in Table 6 at lines  3  and  12 . The economic cost engine  182  uses the physical properties retrieved from the object repository  174  to locate corresponding GUI difference entries (e.g.,  1404  and  1504 ) in the GUI difference model  162 . The GUI difference entries  1404  and  1504  indicate that the window StateList  702  and the WinObject SchoolListbox  714  in the current GAP version  150  correspond to the window School  302  and the WinObject SchoolCombobox  306  in the subsequent GAP version  152 , respectively. In one implementation, the economic cost engine  182  employs the OR lookup logic  172  to traverse the GUI difference model  162  using the physical properties of the GUI objects navigated to by the test script statement vector. The OR lookup logic  172  function returns a GUI element difference entry (e.g.,  504 ,  1404  and  1504 ) from the GUI difference model  162  that represents the GUI object navigated to by the test script statement vector (e.g.,  702 - 704 - 710 - 712 ,  702 - 706 - 708 - 720 - 722 , and  702 - 714 - 726 - 718 ), and the economic cost model logic  196  generates corresponding synthetic GAP change specifiers  185 . 
     
       
         
               
             
               
             
           
               
                 TABLE 6 
               
               
                   
               
               
                 Object Repository 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 − &lt;XYZRep:ObjectRepository 
               
               
                  xmlns:XYZRep=“http://www.vendorXYZ.com/XYZ/ObjectRepository”&gt; 
               
               
                 − &lt;XYZRep:Objects&gt; 
               
               
                 L3 − &lt;XYZRep:Object Class=“Window” Name=“StateList”&gt; 
               
               
                 + &lt;XYZRep:Properties&gt; 
               
               
                 + &lt;XYZRep:BasicIdentification&gt; 
               
               
                 + &lt;XYZRep:CustomReplay&gt; 
               
               
                 L7 − &lt;XYZRep:ChildObjects&gt; 
               
               
                   + &lt;XYZRep:Object Class=“WinObject” Name=“Open File”&gt; 
               
               
                   + &lt;XYZRep:Object Class=“WinObject” Name=“StateListbox”&gt; 
               
               
                   + &lt;XYZRep:Object Class=“WinObject” Name=“Select State”&gt; 
               
               
                   + &lt;XYZRep:Object Class=“WinObject” Name=“Select School”&gt; 
               
               
                   + &lt;XYZRep:Object Class=“WinObject” Name=“SchoolListbox”&gt; 
               
               
                   &lt;/XYZRep:ChildObjects&gt; 
               
               
                  &lt;/XYZRep:Object&gt; 
               
               
                  &lt;/XYZRep:Objects&gt; 
               
               
                  &lt;XYZRep:Parameters /&gt; 
               
               
                  &lt;XYZRep:Metadata /&gt; 
               
               
                  &lt;/XYZRep:ObjectRepository&gt; 
               
               
                   
               
             
          
         
       
     
     Table 7 illustrates the physical properties that may be located in the object repository for the GUI object entry corresponding to the SchoolListbox  714 . 
     
       
         
               
             
               
             
           
               
                 TABLE 7 
               
               
                   
               
               
                 GUI object entry WinObject (“SchoolListbox”) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 − &lt;XYZRep:Object Class=“WinObject” Name=“SchoolListbox”&gt; 
               
               
                 L2 − &lt;XYZRep:Properties&gt; 
               
               
                  − &lt;XYZRep:Property Name=“y” Hidden=“0” ReadOnly=“0” Type=“NUMBER”&gt; 
               
               
                   &lt;XYZRep:Value RegularExpression=“0”&gt;86&lt;/XYZRep:Value&gt; 
               
               
                   &lt;/XYZRep:Property&gt; 
               
               
                  − &lt;XYZRep:Property Name=“x” Hidden=“0” ReadOnly=“0” Type=“NUMBER”&gt; 
               
               
                   &lt;XYZRep:Value RegularExpression=“0”&gt;420&lt;/XYZRep:Value&gt; 
               
               
                   &lt;/XYZRep:Property&gt; 
               
               
                  − &lt;XYZRep:Property Name=“windowstyle” Hidden=“0” ReadOnly=“0” Type=“NUMBER”&gt; 
               
               
                   &lt;XYZRep:Value RegularExpression=“0”&gt;1442906305&lt;/XYZRep:Value&gt; 
               
               
                   &lt;/XYZRep:Property&gt; 
               
               
                  − &lt;XYZRep:Property Name=“windowextendedstyle” Hidden=“0” ReadOnly=“0” Type=“NUMBER”&gt; 
               
               
                   &lt;XYZRep:Value RegularExpression=“0”&gt;512&lt;/XYZRep:Value&gt; 
               
               
                   &lt;/XYZRep:Property&gt; 
               
               
                  − &lt;XYZRep:Property Name=“window id” Hidden=“0” ReadOnly=“0” Type=“NUMBER”&gt; 
               
               
                   &lt;XYZRep:Value RegularExpression=“0”&gt;1182924&lt;/XYZRep:Value&gt; 
               
               
                   &lt;/XYZRep:Property&gt; 
               
               
                  − &lt;XYZRep:Property Name=“width” Hidden=“0” ReadOnly=“0” Type=“NUMBER”&gt; 
               
               
                   &lt;XYZRep:Value RegularExpression=“0”&gt;336&lt;/XYZRep:Value&gt; 
               
               
                   &lt;/XYZRep:Property&gt; 
               
               
                  − &lt;XYZRep:Property Name=“visible” Hidden=“0” ReadOnly=“0” Type=“BOOL”&gt; 
               
               
                   &lt;XYZRep:Value RegularExpression=“0”&gt;−1&lt;/XYZRep:Value&gt; 
               
               
                   &lt;/XYZRep:Property&gt; 
               
               
                  − &lt;XYZRep:Property Name=“regexpwndclass” Hidden=“0” ReadOnly=“0” Type=“STRING”&gt; 
               
               
                   &lt;XYZRep:Value RegularExpression=“0”&gt;WindowsForms10.LISTBOX.app4&lt;/XYZRep:Value&gt; 
               
               
                  &lt;/XYZRep:Property&gt; 
               
               
                  − &lt;XYZRep:Property Name=“object class” Hidden=“0” ReadOnly=“0” Type=“STRING”&gt; 
               
               
                   &lt;XYZRep:Value RegularExpression=“0”&gt;WindowsForms10.LISTBOX.app4&lt;/XYZRep:Value&gt; 
               
               
                   &lt;/XYZRep:Property&gt; 
               
               
                  − &lt;XYZRep:Property Name=“nativeclass” Hidden=“0” ReadOnly=“0” Type=“STRING”&gt; 
               
               
                   &lt;XYZRep:Value RegularExpression=“0”&gt;WindowsForms10.LISTBOX.app4&lt;/XYZRep:Value&gt; 
               
               
                   &lt;/XYZRep:Property&gt; 
               
               
                  − &lt;XYZRep:Property Name=“height” Hidden=“0” ReadOnly=“0” Type=“NUMBER”&gt; 
               
               
                   &lt;XYZRep:Value RegularExpression=“0”&gt;260&lt;/XYZRep:Value&gt; 
               
               
                   &lt;/XYZRep:Property&gt; 
               
               
                  − &lt;XYZRep:Property Name=“enabled” Hidden=“0” ReadOnly=“0” Type=“BOOL”&gt; 
               
               
                   &lt;XYZRep:Value RegularExpression=“0”&gt;−1&lt;/XYZRep:Value&gt; 
               
               
                   &lt;/XYZRep:Property&gt; 
               
               
                 L39  &lt;/XYZRep:Properties&gt; 
               
               
                  − &lt;XYZRep:BasicIdentification&gt; 
               
               
                   &lt;XYZRep:PropertyRef&gt;y&lt;/XYZRep:PropertyRef&gt; 
               
               
                   &lt;XYZRep:PropertyRef&gt;x&lt;/XYZRep:PropertyRef&gt; 
               
               
                  &lt;XYZRep:PropertyRef&gt;windowstyle&lt;/XYZRep:PropertyRef&gt; 
               
               
                   &lt;XYZRep:PropertyRef&gt;windowextendedstyle&lt;/XYZRep:PropertyRef&gt; 
               
               
                  &lt;XYZRep:PropertyRef&gt;width&lt;/XYZRep:PropertyRef&gt; 
               
               
                  &lt;XYZRep:PropertyRef&gt;visible&lt;/XYZRep:PropertyRef&gt; 
               
               
                  &lt;XYZRep:PropertyRef&gt;regexpwndclass&lt;/XYZRep:PropertyRef&gt; 
               
               
                  &lt;XYZRep:PropertyRef&gt;object class&lt;/XYZRep:PropertyRef&gt; 
               
               
                   &lt;XYZRep:PropertyRef&gt;nativeclass&lt;/XYZRep:PropertyRef&gt; 
               
               
                  &lt;XYZRep:PropertyRef&gt;height&lt;/XYZRep:PropertyRef&gt; 
               
               
                   &lt;XYZRep:PropertyRef&gt;enabled&lt;/XYZRep:PropertyRef&gt; 
               
               
                   &lt;/XYZRep:BasicIdentification&gt; 
               
               
                  − &lt;XYZRep:CustomReplay&gt; 
               
               
                   &lt;XYZRep:Behavior Name=“simclass” 
               
               
                        Type=“STRING”&gt;WindowsForms10.LISTBOX.app4&lt;/XYZRep:Behavior&gt; 
               
               
                   &lt;/XYZRep:CustomReplay&gt; 
               
               
                  − &lt;XYZRep:Comments&gt; 
               
               
                   &lt;XYZRep:Comment Name=“miccommentproperty” /&gt; 
               
               
                   &lt;/XYZRep:Comments&gt; 
               
               
                  &lt;XYZRep:ChildObjects /&gt; 
               
               
                 &lt;/XYZRep:Object&gt; 
               
               
                   
               
             
          
         
       
     
       FIG. 8  shows an example economic cost engine system  800  that may implement the economic cost engine  182 . The economic cost engine  182  includes a memory  802  coupled to a processor  804 , and an interface  190 . In one implementation, the interface  190  communicates with the GUI element metadata repository  138  and the GUI difference model  162  to receive GUI element metadata  140  and GUI difference entries  810 , respectively. The interface  190  is connected to a network  806  (e.g., the Internet) in communication with various other systems and resources. In another implementation, the memory  802  includes the GUI element metadata  140 , and GAP change specifier logic  890  that produces the GUI difference model  162  and the GUI element difference entries  810 . The memory  802  also includes script parser logic  812  that receives the current test script  164  and produces the AST  168 , processes the AST  168  as a current test script representation  814 , and produces the test script statement vectors  816  (e.g.,  702 - 704 - 710 - 712 ,  702 - 706 - 708 - 720 - 722 , and  702 - 714 - 726 - 718 ). 
     The memory  802  further includes economic cost model logic  196  that, in one implementation, invokes the OR lookup logic  172  to locate, in the object repository  174 , a GUI object entry  822  referred to by the test script statement vector  816 . In another implementation, the economic cost engine  182  invokes the OR lookup logic  172  to locate, in various external sources, a GUI object entry  822  matching the test script statement vector  816 . When the test script statement vector  816  (e.g.,  702 - 704 - 710 - 712 ,  702 - 706 - 708 - 720 - 722 , and  702 - 714 - 726 - 718 ) employs constants to identify GUI object names, rather than expressions whose values can only be determined at runtime, the OR lookup logic  172  function may use the GUI object name and properties of the GUI object to efficiently locate the correct GUI object entry  822  and locate, in the GUI difference model  162 , a GUI element difference entry  810  matching the GUI object entry  822 . 
     For example, the test script statement vector represented by  702 - 704 - 710 - 712  identifies the window GUI object StateList  202  and the listbox GUI object SchoolListbox  216 , shown in the current test script  164  navigation statement shown at line  6  of  FIG. 6 : 
     Window(“StateList”).WinObject(“SchoolListbox”).Click  19 , 22 . 
     The OR lookup logic  172  locates each GUI object entry  822  for GUI objects  202  and  216 , using the known names of the GUI objects, StateList and SchoolListbox, respectively. The OR lookup logic  172  locates the corresponding GUI element difference entries  1404  and  1504 , in the GUI difference model  162 . In one implementation, the economic cost model logic  196  analyzes the GUI element difference entries  1404  and  1504  and generates one or more corresponding synthetic GAP change specifiers  185 . Using the GAP change specifiers  184 , the economic cost model logic  196  locates, in the economic models  176  repository, one or more corresponding GUI element change cost rules  846  and applies the cost rules to obtain GUI transformation costs  848 . The GUI transformation costs  848  may include costs corresponding to changing the current test script  164  and testing the subsequent GAP version  152 . In other words, the economic cost model logic  196  determines the costs to generate a transformed test script statement that corresponds to GUI objects School  302  and SchoolCombobox  306  and the costs to test the subsequent GAP version  152  using the transformed test script statement: 
     Window(“School”).WinObject(“SchoolCombobox”).Click  294 , 14 . 
     Each GUI element change cost rule  846  may include various attributes, including: a change specifier identifier  850 , system resource utilization identifiers  852 , a GUI change cost estimate  854  that indicates the estimated time and/or resources needed to test a corresponding GUI element change, dependent change specifier identifiers  856 , dependency ranking  858 , quality ranking  860 , complexity ranking  862 , and dependent GUI element change costs  864 . Each economic model, residing in the economic models  176  repository and/or external to the economic models  176  repository that is available to the economic cost model logic  196  through the interface  190 , may include more, fewer, or different GUI element change cost rule  846  attributes. 
     The economic cost model logic  196  uses GAP change specifiers  184  and synthetic GAP change specifiers  185  to locate applicable GUI element change cost rules  846 , in the economic models  176  repository, corresponding to change specifier identifiers  850 . The system resource utilization identifiers  852  indicate the resources used to test a particular GUI element change. In one implementation, the system resource utilization identifiers  852  have values from 1 to 10 that identify the amount of a test environment&#39;s processing and infrastructure capacity needed to test a corresponding GAP change. For example, a system resource utilization identifier  852  with a value of 3, corresponding to the test environment&#39;s processing capacity, may indicate that one-third of the available processing capacity is needed to test a corresponding GAP change. A system resource utilization identifier  852  with a value of 10, corresponding to the test environment&#39;s processing capacity, may indicate that most of the available computing resources (e.g., processing capacity) will be needed to test a corresponding GAP change. 
     In another implementation, the system resource utilization identifiers  852  provide descriptions of the resources needed to test a corresponding GAP change. For example, the system resource utilization identifiers  852  may itemize the skills of testers, system components (e.g., input and output devices, and network bandwidth) and the priority settings to be assigned to system processes used to test a corresponding GUI element change. In one implementation, the system resource utilization identifiers  852  provide a combination of discrete values that indicate the test environment&#39;s processing capacity and the itemized descriptions of the various resources needed to test the corresponding GUI element change. 
     The economic cost model logic  196  may locate other applicable GUI element change cost rules  846  that depend from a particular GUI element change cost rule  846  identified by a change specifier identifier  850 , using dependent change specifier identifiers  856 . The dependent change specifier identifiers  865  may identify one or more corresponding GUI element change cost rules  846  that depend from the GUI element change corresponding to the change specifier identifier  850 . For example, a change in the class of a parent GUI object from a listbox to a combobox (e.g., SchoolListbox  216  and SchoolCombobox  306 ) may impose GUI element changes to children GUI objects of the parent GUI object, so that a change specifier identifier  850  corresponding to a particular GAP change specifier  184  and/or synthetic GAP change specifier  185  identifies one or more dependent change specifiers identifiers  856 . 
     In one implementation, the dependency ranking  858  is a value from 0 to 10 that indicates the level of dependency a GAP may have on a particular GUI element. The dependency ranking  858  may correspond to the visibility and scope of a GUI element. For example, the change of the window StateList  202  in the current GAP  150  to School  302  in the subsequent GAP  152 , as shown in  FIG. 14 , may correspond to a dependency ranking  858  of 10, while the change of a value in the StateListbox  212  to a value in the StateListbox  304 , as shown in  FIG. 5 , may correspond to a dependency ranking  858  of 4. The economic cost model logic  196  uses the dependency ranking  858  to facilitate obtaining the GUI transformation costs  848 . In one implementation, the economic cost model logic  196  uses the dependency ranking  858  to determine how and/or whether to use the GUI change efficiency factor  886 , discussed in further detail below. 
     In one implementation, the quality ranking  860  is a value from 1 to 10 that indicates the contribution to the quality of the subsequent GAP version  152  made by the GUI element change. For example, a particular GUI element change that enforces integrity checking on a GUI element corresponding to a high dependency ranking  858  value may correspond to a quality ranking  860  of 10. In another example, a GUI element change that is unperceivable and/or corresponds to a low dependency ranking  858  value may correspond to a quality ranking  860  of 0. In one implementation, the economic cost model logic  196  uses a user selectable quality preference identifier to generate the test script transformation cost report  186  with GUI transformation costs  848  corresponding to quality rankings  860  meeting or exceeding the quality preference identifier, so that test plans may be evaluated based on quality factors. 
     In one implementation, the complexity ranking  862  is a value from 1 to 10 that indicates the difficulty level of testing the corresponding GUI element change, where a complexity level of 10 is a high level of complexity and a level of 0 is a low level of complexity. In another implementation, the complexity ranking  862  indicates the contribution to the level of complexity of the subsequent GAP version  152  made by the GUI element change. For example, a particular GUI element change that enforces integrity checking on a GUI element corresponding to a high dependency ranking  858  value may correspond to a complexity ranking  862  of 10. In another example, a GUI element change that is unperceivable and/or corresponds to a low dependency ranking  858  value may correspond to a complexity ranking  862  of 0. In one implementation, the economic cost model logic  196  uses a user selectable complexity preference identifier to generate the test script transformation cost report  186  with GUI transformation costs  848  to complexity rankings  862  meeting or exceeding the complexity preference identifier, so that test plans may be evaluated based on complexity. 
     The dependent GUI element change costs  864  may represent an aggregated GUI transformation cost  848  corresponding to the dependent change specifier identifiers  856 . In one implementation, the economic cost model logic  196  uses the dependent GUI element change costs  864 , rather than retrieving each GUI element change cost rule  846  corresponding to the one or more dependent change specifier identifiers  856 , to generate the test script transformation cost report  186 . 
     In one implementation, the economic cost model logic  196  uses user selectable preference identifiers  866  to locate GUI element change cost rules  846  based on discrete values and/or ranges of values for one or more of the system resource utilization identifiers  852 , GUI change cost estimate  854 , dependency ranking  858 , quality ranking  860 , complexity ranking  862  and dependent GUI element change costs  864 . The preference identifiers  866  identify the GUI transformation costs  848  used to generate the test script transformation cost report  186 , based on one or more of the change specifier identifier  850 , a system resource utilization identifier  852 , a GUI change cost estimate  854  that indicates the estimated time and/or resources (e.g., money and labor) to test a corresponding GUI element change, dependent change specifier identifiers  856 , dependency ranking  858 , quality ranking  860 , complexity ranking  862 , and dependent GUI element change costs  864 . 
     The GUI transformation cost  848  may include a time component and resource component. The time component of the GUI transformation cost  848  may indicate the elapsed time needed to change a test script statement and/or test a corresponding GUI element change. The resource component of the GUI transformation cost  848  may indicate the money, areas of skill and/or system infrastructure (e.g., human and technological units) needed to change a test script statement and/or test a corresponding GUI element change. 
     Recall that the economic cost engine  182  may generate test script transformation cost reports  186  based on multiple combinations of available information, including: 1) GAP change specifiers  184 ; 2) GAP change specifiers  184  and a current test script  164 ; 3) GAP change specifiers  184 , a current test script  164  and a current GAP version  150  (e.g., a current GAP tree model); 4) a current test script  164 , and a GUI difference model  162  with GUI element difference entries; and 5) GAP change specifiers  184 , a current test script  164 , and a GUI difference model  162 . The various combinations of available information are used by the economic cost engine  182  to analyze received GAP change specifiers  184  and/or generated synthetic GAP change specifiers  185  that are used by the economic cost model logic  196  to locate and retrieve GUI transformation costs  848  and generate test script transformation cost reports  186 . 
     In one implementation, the economic cost engine  182  receives GAP change specifiers  184  that the economic cost engine  182  uses to locate and retrieve GUI element change cost rules  848  from the economic models  176  repository. The received GAP change specifiers  184  may have resulted from prior analysis of a current GAP version  150 , a current test script  164  and/or a GUI difference model  162 . In one implementation, the economic cost engine  182  may receive GAP change specifiers  184  and a current test script  164 . The script parser logic  812  produces the test script statement vectors  816  based on the current test script  164 . The economic cost model logic  196  analyzes the test script statement vectors  816  to generate synthetic GAP change specifiers  185 . The economic cost model logic  196  uses the received GAP change specifiers  184  and generated synthetic GAP change specifiers  185  to locate and retrieve GUI element change cost rules  848  from the economic models  176  repository. In one implementation, the received GAP change specifiers  184  and generated synthetic GAP change specifiers  185  are indistinguishable as to their origin such that the economic cost model logic  196  processes the received GAP change specifiers  184  and generated synthetic GAP change specifiers  185  uniformly, regardless of their origin. 
     In another implementation, the economic cost engine  182  receives GAP change specifiers  184 , a current test script  164  and a current GAP version  150 . The economic cost engine  182  analyzes the GAP change specifiers  184  and the current GAP version  150  (e.g., current GAP tree model) to generate synthetic GAP change specifiers  185 . The economic cost engine  182  analyzes the test script statement vectors  816  corresponding to the current test script  164  and the GUI difference model  162  to generate synthetic GAP change specifiers  185 . The economic cost model logic  196  uses the received GAP change specifiers  184  and generated synthetic GAP change specifiers  185  to locate and retrieve GUI element change cost rules  848  from the economic models  176  repository and generate the test script transformation cost report  186 . 
     In one implementation, the economic cost engine  182  receives a current test script  164  and a GUI difference model  162 , without GAP change specifiers  184 . The economic cost engine  182  analyzes the test script statement vectors  816  corresponding to the current test script  164  and the GUI difference model  162  to generate synthetic GAP change specifiers  185 . 
     In one implementation, the economic cost engine  182  receives GAP change specifiers  184 , a current test script  164 , a GUI difference model  162  corresponding to the GAP version  150  and a subsequent GAP version  152 . The economic cost engine  182  analyzes the test script statement vectors  816  corresponding to the current test script  164  and the GUI difference model  162  to generate synthetic GAP change specifiers  185 . The economic cost engine  182  uses the received GAP change specifiers  184  and generated synthetic GAP change specifiers  185  to locate and retrieve GUI element change cost rules  848  from the economic models  176  repository and generate the test script transformation cost report  186 . 
     In one implementation, the accuracy of the GUI transformation costs  848  varies due to the granularity of the information received by the economic cost engine  182 . For example, the GUI transformation costs  848  generated as a result of the economic cost engine  182  receiving GAP change specifiers  184 , a current test script  164 , and a GUI difference model  162  may have a higher level of accuracy than the GUI transformation costs  848  generated based solely on received GAP change specifiers  184 . The economic cost engine  182  may employ various economic models to preserve the accuracy of the GUI transformation costs  848  and compensate for the varying granularities of information provided to the economic cost engine  182 . 
     In one implementation, GAP change specifiers  184  and/or synthetic GAP change specifiers  185  include a model specifier  868 , a GUI change frequency  870 , skill coefficients  872 , complexity identifier  874 , quality identifier  876 , percent of change  878 , wrong path-delete type  880 , wrong path-same type  882  and changed element type  884  specifiers. The model specifier  868  specifies one or more economic models to use from among multiple economic models accessible by the economic model logic  196 . In one implementation, the model specifier  868  specifies one or more economic models for the economic cost model logic  196  to use corresponding to the varying granularities of information provided to the economic cost engine  182 , so that the accuracy of the GUI transformation costs  848  are preserved. For example, the model specifier  868  may specify models corresponding to one or more of the multiple combinations of available information received by the economic cost engine  182 , including: 1) model-1 for GAP change specifiers  184 ; 2) model-2 for GAP change specifiers  184  and a current test script  164 ; 3) model-3 for GAP change specifiers  184 , a current test script  164  and a current GAP version  150 ; 4) model-4 for a current test script  164  and a GUI difference model  162  with GUI difference entries  810 ; and 5) model-5 for GAP change specifiers  184 , a current test script  164 , and a GUI difference model  162  with GUI difference entries  810 . 
     The GUI change frequency  870  indicates the number of occurrences of a particular GUI element change. In one implementation, the economic cost model logic  196  includes a user adjustable GUI change efficiency factor  886  that indicates whether a GUI change frequency  870  above a particular threshold results in a lower GUI transformation cost  848 . For example, a GUI change efficiency factor  886  of 0.50 indicates that the GUI transformation cost  848  for each change above a threshold of 100 occurrences for a given GUI element change are adjusted by 50 percent. In other words, where a particular GUI element change is identified to have 120 occurrences, the economic cost model logic  186  applies the GUI change efficiency factor  886  of 0.50 to the GUI transformation cost  848  for the 20 changes above the threshold of 100. In another example, a GUI change efficiency factor  886  of 0.00 may indicate that no efficiency is realized regardless of the GUI change frequency  870  value. 
     In one implementation, the skills coefficients  872  include one or more coefficients that are used to describe the level of experience of the testers who are expected to test the subsequent GAP version  152 . The skills coefficients  872  may include individual coefficients for specific areas of testing experience. For example, the skills coefficients  872  may correspond to the skill and experience level of testers according to particular phases of testing such as unit, integration, system and final test phase so that each phase is represented by one or more coefficients. In another example, the skills coefficients  872  may correspond to skills and experience corresponding to testing particular aspects of the subsequent GAP version  152 , such as security and user authentication, numerical computations specific to the GAP, and network and infrastructure. 
     In another implementation, the skills coefficients  872  are calibrated based on performance metrics located in a performance metrics repository  198  and/or cost reports repository  888 . GAP change specifiers  184  and/or synthetic GAP change specifiers  185  may be constructed and/or generated from historical performance metrics found in a performance metrics repository  198  and/or cost reports repository  888 . The skills coefficients  872  of the constructed GAP change specifiers  184  and/or synthetic GAP change specifiers  185  may be adjusted over multiple iterations to obtain GUI transformation costs  848  and test script transformation cost reports  186  that are within acceptable margins of variance to the actual costs reflected in the performance metrics repository  198 . The accuracy of the GUI transformation costs  848  obtained by the economic cost model logic  196  may be based on how well the skills coefficients  872  are calibrated to reflect the testing resources available to test the subsequent GAP version  152 . In one implementation, the skills coefficients  872  influence the complexity identifier  874 , discussed in further detail below. 
     The economic cost model logic  196  uses the skills coefficients  872  to obtain the GUI transformation costs  848 . For example, a skills coefficient  872  value of 1.0 may indicate that testers with little experience are expected to be used to test the subsequent GAP version  152  and higher GUI transformation costs  848  may result to reflect the low experience. In another example, a skills coefficient  872  value of 8.0 may indicate testers with higher than average testing experience and lower GUI transformation costs  848  may result that reflect the higher than average experience. The economic cost model logic  196  may analyze whether the skills coefficients  872  and complexity ranking  862  correlate, and obtain correspondingly higher or lower GUI transformation costs  848 . For example, the skills coefficients  872  may indicate that the testers are capable of testing a GAP with a particular level of complexity, as indicated by the complexity ranking  862 , so that lower GUI transformation costs  848  are obtained. In another example, the skills coefficients  872  may indicate that the testers lack a skill and experience level for testing a GAP with a particular level of complexity corresponding to the complexity ranking  862 , so that higher GUI transformation costs  848  are obtained to reflect the lack of skills and experience of the testers and the expected time and resources to test the subsequent GAP version  152 . 
     In one implementation, the complexity identifier  874  numerically identifies the level of complexity of a GUI element change (e.g., values 0 to 10), determined by the economic cost model logic  196 , corresponding to a generated synthetic GAP change specifier  185 . In another implementation, the complexity identifier  874  identifies the level of complexity determined by a tester and received by the economic cost model logic  196  with the GAP change specifier  184 . Distinguishing the complexity identifier  874  of the GAP change specifier  184  and/or synthetic GAP change specifier  185  from the complexity ranking  858  of the GUI element change cost rule  846 , the complexity identifier  874  represents analysis that is external to the economic models  176  repository. The economic cost model logic  196  may analyze the complexity ranking  862  and complexity identifier  874  to assess the accuracy of the GUI transformation costs  848  obtained by applying the GUI element change cost rule  846 . 
     For example, the economic cost model logic  196  may determine that the complexity ranking  862  and complexity identifier  874  corresponding to a particular GUI element change are within an acceptable margin of variance such that the GUI transformation cost  848  is not adjusted as a result. In another example, the economic cost model logic  196  may determine that the complexity ranking  862  and complexity identifier  874  corresponding to a particular GUI element change are outside of an acceptable margin of variance and the GUI transformation costs  848  are adjusted upward by a multiplier. The margin of variance and the multiplier, determined by analyzing the complexity ranking  862  and complexity identifier  874 , may be user selectable and/or adjustable. In one implementation, the complexity identifier  874  is based on the skills coefficients  872  such that the complexity of a GUI element change is assessed relative to the skills and experience of the available testers. The skills coefficients  872  may be calibrated so that the complexity ranking  862  and the complexity identifier  874  generated by the economic cost model logic  196  are within an acceptable margin of variance. 
     In one implementation, the quality identifier  876  numerically identifies the level of quality contributed to by a GUI element change (e.g., values 0 to 10), determined by the economic cost model logic  196 , corresponding to a generated synthetic GAP change specifier  185 . In another implementation, the quality identifier  876  identifies the level of quality determined by a tester and received by the economic cost model logic  196  with the GAP change specifier  184 . Distinguishing the quality identifier  876  of the GAP change specifier  184  and/or synthetic GAP change specifiers  185  from the quality ranking  860  of the GUI element change cost rule  846 , the quality identifier  876  represents analysis that is external to the economic models  176  repository. The economic cost model logic  196  may analyze the quality ranking  860  and quality identifier  876  to assess the accuracy of the GUI transformation costs  848  obtained by applying the GUI element change cost rule  846 . For example, the economic cost model logic  196  may determine that the quality ranking  860  and quality identifier  876  corresponding to a particular GUI element change are within an acceptable margin of variance such that the GUI transformation cost  848  is not adjusted as a result. In another example, the economic cost model logic  196  may determine that the quality ranking  860  and quality identifier  876  corresponding to a particular GUI element change are outside of an acceptable margin of variance and the GUI transformation costs  848  are adjusted upward by a multiplier. The margin of variance and the multiplier, determined by analyzing the quality ranking  860  and quality identifier  876 , may be user selectable and/or adjustable. 
     In one implementation, the economic cost engine  182  receives a GAP change specifier  184  that includes a percent of change  878  value, a current test script  164  and a current GAP tree model corresponding to a current GAP version  150  that the economic cost engine  182  uses to generate synthetic GAP change specifiers  185 , and locate and retrieve GUI element change cost rules  848  from the economic models  176  repository. For example, the economic cost model logic  196  analyzes the current GAP version  150  (e.g., represented by a current GAP tree model) and generates synthetic GAP change specifiers  185  that reflect a percentage of change to the current GAP version  150  corresponding to the percent of change  878  value (e.g., ranging from 1 to 100). The economic cost model logic  196  analyzes the current GAP version  150  and identifies a set of proposed GUI elements changes that correspond to the percent of change  878  value. The economic cost model logic  196  may identify the proposed GUI elements by analyzing the GUI elements in the GAP tree model of the current GAP version  150  in a random order, the order in which the GUI elements are presented in the tree model from top to bottom or from bottom to top. 
     In one implementation, the proposed GUI element changes may be determined based on the complexity identifier  874  and/or quality identifier  876  included in the received GAP change specifier  184 . For example, the economic cost model logic  196  receives a GAP change specifier  184  that includes a complexity identifier  874  value of 1 and quality identifier  876  value of 2, and for each of the proposed GUI elements to be changed, determines proposed changes corresponding to the complexity identifier  874  value of 1 and the quality identifier  876  value of 2. The economic cost model logic  196  may locate, in the performance metrics repository  198  and/or cost reports repository  888 , proposed GUI element changes corresponding to the complexity identifier  874  values and the quality identifier  876  values. In one implementation, the economic cost model logic  196  generates synthetic GAP change specifiers  185 , as a result of analyzing the proposed GUI element changes. In another implementation, the economic cost model logic  196  identifies proposed GUI element changes corresponding to the complexity identifier  874 , the quality identifier  876  and skill coefficients  872 . 
     The economic cost model logic  196  analyzes the current test script  164  and GUI difference model  162  to generate synthetic GAP change specifiers  185  based on validated GUI element changes (e.g., GUI element difference entries). For example, the economic cost model logic  196  determines test script statement vectors  816  that need modification because GUI objects that are referenced in the current test script  164  and exist in the current GAP version  150  that do not exist in the subsequent GAP version  152 , and the economic cost model logic  196  generates synthetic GAP change specifiers  185  that reflect the needed changes to the current test script  164 . The economic cost model logic  196  identifies changes to test script statement vectors  816  that set the values of GUI objects that are compatible with the class of that GUI objects, so that constraints imposed on the GUI objects as a result of a change are not violated. In one implementation, the economic cost model logic  196  verifies that incorrect operations are not specified by GAP change specifiers  184  and/or synthetic GAP change specifiers  185  used to obtain GUI transformation costs  848 . 
     The economic cost model logic  196  may infer GUI class information regarding a GUI object that is present in a navigation path of test script statement vectors  816 , and whose presence is not explicitly defined. For example, when the test script statement vector  816  employs expressions that identify GUI objects whose values can only be determined at runtime, the OR lookup logic  172  may use path traversal logic  824  to identify the possible corresponding GUI object entries  822  and GUI element difference entries  810  in the object repository  174  and GUI difference model  162 , respectively. The economic cost model logic  196  then identifies the valid GUI object entries  822  that may substitute for the expressions and GUI element difference entries  810  that satisfy valid test script statement vectors  816 , and the economic cost model logic  196  generates corresponding synthetic GAP change specifiers  185 . 
     For example, consider the test script statement vector  816 : VBWindow(“s”).VBWindow(e1).VBWindow(e2).VBWindow(“d”), where the source node GUI object is named “s”, the destination node GUI object is named “d”, but expressions e1 and e2 compute values of intermediate nodes in the navigation path at runtime. The traversal logic  824  determines intermediate nodes (GUI objects) that may be included in the possible navigation paths identified by the source node “s” and destination node “d”. The path traversal logic  824  analyzes the GUI difference model  162  to identify possible constant substitutions for e1 and e2, for example, “a” and “f”, so that the test script statement vector  816  formed by the substitute GUI objects in the navigation path expression “s.a.f.d” can be validated by economic cost model logic  196 . By identifying the possible navigation paths leading to the destination node d starting with the source node ‘s’ the economic cost model logic  196  can conclude whether to generate a synthetic GAP change specifier  185  based on the substitute GUI objects. In the event the traversal logic  824  does not identify at least one navigation path, then the transformed test script statement  828  is invalid. Alternatively, in the event the traversal logic  824  identifies navigation paths leading from ‘s’ to ‘d’ by traversing two objects (e.g., e1 and e2), then the transformed test script statement  828  may be valid provided that expressions e1 and e2 evaluate to the names of the nodes in the discovered navigation paths. The traversal logic  824  infers the possible names computed by expressions e1 and e2 at compile time. In other words, there is a direct correlation between the complexity of test scripts and the economic cost to transform test scripts and use those test scripts to test subsequent GAP versions  152 . The complexity is a function of the number of referenced GUI objects and operations on the GUI objects, as well as the amount of logic needed to process the data that is extracted and placed into those GUI objects. 
     A formal description of the traversal logic  824  is provided with reference to  FIG. 16 . Expressions e1 and e2 may be replaced with the object name variables a and β correspondingly, and the original expression is converted into traversal strategy S=s→═→β→d. The function ‘first(s)’ computes a set of edges that can be traversed from node s. These edges lead to a set of objects designated by the variable a. Function ‘first(s)’ may be computed using a graph reachability algorithm, included in the path traversal logic  824 , and the path traversal logic  824  returns edges that may navigate to the destination node. According to  FIG. 16 , α={a, b, c}. Then for each element of a, function ‘first’ may be computed. As a result, β={e, f, g} are obtained, where ‘first(a)’={e, g}, ‘first(b)’={e}, and ‘first(c)’={f}, and ‘first(e)’={Ø}, ‘first(f)’={d}, and ‘first(g)’={d}. From the computed node values the path traversal logic  824  forms a work-list W that includes a set of all computed paths, W={(s, a, e), (s, a, g, d), (s, b, e), (s, c, f, d)}. The path traversal logic  824  analyzes each navigation path of W to determine whether the navigation path contains nodes ‘s’ and ‘d’. Navigation paths identified by the path traversal logic  824  to include nodes ‘s’ and ‘d’, as source and destination nodes, are considered as valid navigation paths. In the event no navigation paths are identified by the traversal logic  824 , then the test script statement vector  816  is invalid because the target GUI element cannot be reached starting from the specified beginning GUI element. 
     Referring again to  FIG. 16 , an example of an invalid expression is VBWindow(“s”).VBWindow(e1). VBWindow(e2).VBWindow(e3).VBWindow(“d”). All navigation paths between nodes s and d have at most two objects. Therefore, no matter what values are computed at runtime for expressions e1, e2, and e3 the expressions cannot represent objects in a valid navigation path between the source and the destination objects. Another example of an invalid expression is VBWindow(“s”).VBWindow(“b”).VBWindow(e1).VBWindow(“d”), because no value for the expression e1 exists that makes the navigation path valid (i.e. that forms a complete path from ‘s’ to ‘d’). 
     The economic cost model logic  196  may infer GUI class information regarding GUI objects that are present in the navigation path of test script statement vectors  816 . The economic cost model logic  196  identifies GAP change specifiers  184  and/or synthetic GAP change specifiers  185  that resolve test script statement vectors  816  that attempt to access GUI objects that do not exist in a subsequent GAP version  152  and/or attempt to set a value of a GUI object that is not compatible with the type of the GUI object. The economic cost model logic  196  type checks test script statement vectors  816  against the GUI difference model  162  before generating corresponding GAP change specifiers  184 . 
     The economic cost model logic  196  uses inheritance and sub-typing relations between classes of GUI objects to validate received GAP change specifiers  184  and generate valid synthetic GAP change specifiers  185 . The concept of class includes hierarchical containments (e.g., GUI scopes and system hierarchies). The object repository  174  and the GUI difference model  162  include GUI class information (e.g., annotating the classes of GUI objects) for each GUI object entry  822  and GUI element difference entry  810 . For example, referring to line  1  of Table 7, the SchoolListBox is a WinObject class with properties listed at lines  3 - 39 . In another example, referring to  FIGS. 5 ,  14  and  15 , at line  1  of each GUI difference entry (e.g.,  504 ,  1404  and  1504 ) the GUIElement Type is indicated. The class of each GUI object is indicated as shown in  FIGS. 5 ,  14  and  15  at lines  7 ,  8  and  8 , respectively. The class of a GUI object indicates that the GUI object includes particular attributes, properties and/or traits in common with other GUI objects of the same class that may be extended to and/or inherited by child GUI objects. For example,  FIG. 5  at line  7  indicates that the StateListbox GUI object is of a WindowsForms10.ListBox.app4 class that includes values, as indicated at line  11  of  FIG. 5 . In other words, one property of GUI objects of WindowsForms10.ListBox.app4 is that these GUI objects are expected to have values. Class is a concept that a GUI framework uses to classify GUI objects. For example, class ListBox defines shape, functionality, and the rules of interactivity for GUI objects of this class. Assigning classes to GUI objects facilitates the economic cost model logic  196  to trace changes between successive GAP versions (e.g.,  150  and  152 ) and perform extended checking on the correctness of operations on GUI objects. 
     Referring again to  FIG. 8 , in one implementation, the economic cost model logic  196  determines whether a GUI object has changed and sets the GUI element change status  834 . For example, the GUI element change status  834  may use a numerical indicator of 0, 1, and 2, respectively, to indicate no change, and a change with and without a particular constraint violation. The economic cost model logic  196  may use the GUI element change status  834  to facilitate identifying the appropriate GAP change specifiers  184  and/or synthetic GAP change specifiers  185 . 
     In another implementation, the GUI element change status  834  is a message that provides a detail description of a change. The GUI element change status  834  may also indicate with a numerical indicator (e.g., −1) that the GUI object has been deleted from the subsequent GAP version  152 . When a GUI object has been deleted from the subsequent GAP version  152 , the economic cost model logic  196  generates one or more synthetic GAP change specifiers  185  that specify corresponding changes to the current test script  164  and the current GAP version  150 . In one implementation, the economic cost model logic  196  generates synthetic GAP change specifiers  185  that correspond to different, but programmatically equivalent, approaches to changing the current test script  164  and the current GAP version  150 , so that a programmer may evaluate the GUI transformation costs  848  and test script transformation cost report. 
       FIG. 9  shows a flow diagram  900  for retrieving the properties of a GUI object entry  822  from an object repository (OR)  174 . The script parser logic  812  parses the test script statement vector  816  into an ordered sequence of nodes that represent functions and arguments that navigate to GUI objects ( 902 ). The script parser logic  812  evaluates the first node of the ordered sequence of nodes ( 904 ), and identifies the first node as the source node and assigns a sequence identifier indicating the position of the source node in the ordered sequence ( 906 ). The script parser logic  812  evaluates the next node of the order sequence of nodes to determine whether the next node is the last node ( 908 ), and identifies the next node as an intermediate node when the next node is not the last node ( 910 ). The intermediate node is assigned a sequence identifier indicating the position of the intermediate node in the ordered sequence. The script parser logic  812  may identify all intermediate nodes between the source node and the destination node. 
     The script parser logic  812  identifies the last node in the ordered sequence as the destination node and assigns a sequence identifier to the destination node that indicates the position of the destination node in the ordered sequence ( 912 ). The OR lookup logic  172  performs an object repository lookup for each GUI object corresponding to the ordered sequence of nodes to which the test script statement vector navigates so that each GUI object entry  822  is identified ( 914 ). In one implementation, the ordered sequence of nodes is used by the path traversal logic  824  and economic cost model logic  196  to validate the statements of the current test script  164 , and/or validate received GAP change specifiers  184  and generate valid synthetic GAP change specifiers  185 . In one implementation, the economic cost engine  182  uses the ordered sequence of nodes to infer GUI class and inheritance (subclass) information for GUI objects. Where at least one of the source, destination and/or the intermediate nodes are expressions that can only be identified at run-time, the path traversal logic may identify possible GUI object entries  822 , and the economic cost model logic  196  determines the GUI object entries  822  that satisfy the test script statement vector  816 . The OR lookup logic  172  retrieves the properties of the GUI object entries  822  to which the test script statement vector navigates ( 916 ). 
       FIG. 10  shows a flow diagram  1000  for identifying a GUI difference entry  810  corresponding to a GUI object entry  822 . The OR lookup logic  172  receives the properties of the GUI objects corresponding to the source, destination and all intermediate nodes of the test script statement vector  816 . In one implementation, the OR lookup logic  172  employs the path traversal logic  824  to identify possible GUI difference entries  810  corresponding to the navigation paths identified by a source node and a destination node to which a test script statement vector navigates ( 1002 ). Where at least one of the GUI element difference entries  810  is an expression that can only be identified at run-time, the path traversal logic  824  identifies one or more possible GUI difference entries  810  that form a navigation path between the source node and the destination node ( 1004 ). The path traversal logic  824  determines whether the GUI difference entries  810  form a valid navigation path between corresponding source and destination nodes GUI difference entries  810  ( 1006 ). The GUI economic cost model logic  196  determines whether the GUI difference entries  810  that form the navigation path are valid ( 1008 ). 
     The economic cost model logic  196  identifies the GUI element difference entries  810  that correspond to each of the GUI object entries  822  forming a valid navigation path ( 1010 ). The economic cost model logic  196  determines the synthetic GAP change specifiers  185  to generate and/or validates the GAP change specifiers  184  based on the type of GUI element change (e.g.,  880 ,  882 ,  884  and/or GUI element change status  834 ), based on analyzing the GUI object entry  822  and GUI element difference entry  810  ( 1012 ). The economic cost model logic  196  generates valid synthetic GAP change specifiers  185  corresponding to the type of GUI element change identified. When the path traversal logic  824  identifies a navigation path that traverses an invalid number of GUI element difference entries  810  between corresponding source and destination node GUI difference entries  810 , the path traversal logic  824  indicates that the navigation path is invalid ( 1014 ). 
       FIG. 11  shows a transformed test script  178  for the subsequent GAP version  152 . The economic cost model logic  196  may generate synthetic GAP change specifiers  185  that specify the changes needed to obtain the transformed test script  178 . For example, the economic cost model logic  196  generates synthetic GAP change specifiers  185  for lines  1 - 3  of the current test script  164 , shown in  FIG. 6 , corresponding to transformed test script lines  1 ,  5 - 7 , shown in  FIG. 11 . In one implementation, the GUI difference model  162  and the GUI element metadata provide the GUI class, GUI typing and mapping information necessary for the economic cost model logic  196  to infer lines  2 - 4  of the transformed test script  178 , given that the “university.data” in line  6  represents a destination in a path traversal from which valid GAP change specifiers  184  and/or synthetic GAP change specifiers  185  may be determined. In another example, the GUI difference model  162  and/or the GUI element metadata include GUI class and mapping information that the economic cost engine  182  uses to generate one or more synthetic GAP change specifiers  185  that specify how to transform line  16  of the current test script  164 , as shown in  FIG. 6 , that refers to WinObject “Save File” into lines  24 - 25  that refer to a “Save File” child GUI object of the WinObject “menuStrip1”. 
       FIG. 12  shows a flow diagram  1200  for generating a synthetic GAP change specifier  185 . In one implementation, the economic cost model logic  196  validates GAP change specifiers  184  and/or generates synthetic GAP change specifiers  185  that specify the type of GUI object changes between successive releases of GAPs, including: (A) a new GUI object added to a subsequent GAP version  152 ; (B) a GUI object is deleted from a subsequent GAP version  152 ; (C) the values of one or more attributes of a GUI object are modified; (D) the values of a GUI object are modified between successive GAP versions; and (E) the type of a GUI object is different. The economic cost engine  182  analyzes the GUI objects referred to in the current test script  164 , the current GAP version  150  and the GAP change specifiers  184  ( 1202 ). The economic cost engine  182  retrieves the properties of each GUI object (e.g., GUI object entries  822 ) from the object repository  174 , and locates a corresponding GUI element difference entry  810  in the GUI difference model  162  ( 1204 ). In one implementation, the economic cost engine  182  receives a current GAP tree model representation of a current GAP version  150  from the GUI difference model  162  and GAP change specifiers  184 , and generates synthetic GAP change specifiers  185 , using GAP change specifier logic  890 . The economic cost model logic  196  analyzes the GUI object changes ( 1206 ). 
     GUI object changes of types A ( 1208 ) and B ( 1210 ) occur when GUI objects are added and removed correspondingly from current GAP version  150  and subsequent GAP version  152 . For example, adding the WinObject menustrip1  308  to the subsequent GAP version  152  is a type A change, while removing the WinObject “Select School”  204  is a type B GUI object change. Referring to  FIG. 4 , notice that the “Select School” has been removed at  412 . 
     An example of a type C change ( 1212 ) is the change of the window name from StateList  202  to School  302 . Adding or removing values from GUI objects such as list and combo boxes are examples of modifications of the type D change ( 1212 ). For example, the listbox StateListbox  212  in current GAP version  150  is identified in the subsequent GAP version  152  as StateListbox  304 , and referring to the GUI difference entry  504  the values for SeqNumber=“8” are “District of Columbia” and “Florida” for successive GAP versions, respectively. Changing the “type” of a GUI object may include replacing a class of the window that is used to represent the object and/or changing the high-level concept that describes the values that the GUI object takes. For example, changing the type of the static label to a read-only combo box is a modification of the type E ( 1212 ). Another example of a type E change includes the change of the listbox “SchooListbox”  216  to a combobox “SchoolCombobox”  306 . 
     The economic cost model logic  196  receives GAP change specifiers  184  and generates synthetic GAP change specifiers  185  that include wrong path-delete type  880  wrong path-same type  882  and changed element type  884  specifiers. Wrong path-delete type  880  specifies that a GUI object in the current GAP version  150  may have been deleted in the subsequent GAP version  152  (e.g., see “Select School”  218  and  412  as shown in  FIG. 4 ), although the current test script  164  refers to the GUI object ( 1214 ). Wrong path-same type  882  specifies that a GAP change may result in a read and/or write to the wrong GUI object. For example, a method may be invoked on the wrong GUI object based on a particular GAP change. Wrong path-same type  882  specifies that a GUI object in a current GAP version  150  has been modified and/or another GUI object has been added to the subsequent GAP version  152  that may result in the wrong GUI object being navigated to by a test script statement ( 1216 ). 
     For example, consider the statement in lines  2  and  6  of the current test script  164  and transformed test script  178 , respectively: 
     Window(“StateList”).Dialog(“Open”).WinListView(“SysListView32”).Select “university.data”. 
     The statement selects “university.data” from a WinListView “SysListView32”. However, lines  2 - 4  of the transformed test script  178  may navigate to and invoke the Select method on the wrong GUI object “university.data”, because the GUI objects referenced in lines  2 - 4  of the transformed test script  178  are new GUI objects that are not referenced in the current test script  164 . Thus, when the properties of existing GUI objects are modified and/or other GUI objects are added into a subsequent GAP version  152 , the result of interference of these operations is that transformed test script statements that result from applying GAP change specifiers  184  and/or synthetic GAP change specifiers  185  to current test script statement vectors  816  may access and read values of objects that are different from those as originally intended. 
     Changed-element  884  specifies that the type, properties, and/or default values of a GUI object referenced by a test script statement vector  816  have changed in the subsequent GAP version  152  ( 1218 ). For example, the GUI difference entry  504  indicates that there are different values for SeqNumber=“8” are “District of Columbia” and “Florida” for successive GAP versions, and the economic cost model logic  196  may generate a synthetic GAP specifier  185  that includes a change-element  884  correspondingly. Change-element  884  may also specify that new constraints have been imposed on a GUI object that conflict with test script statement vectors  816 , for example, attempting to write data to a previously writable text box that has been changed to a read-only text box. Referring to the GUI element difference entry shown in Table 8, the WinObject “AcadScale” referred to in the current test script  164  at line  8  is an editable object that has been transformed into the WinObject “Academics (1-5)” in the subsequent GAP version  152  where the object is read-only. The economic cost model logic  196  validates GAP change specifiers  184  and/or generates the synthetic GAP change specifier  185  with the GAP change type specified ( 1220 ) and the GUI element change status  834  is updated ( 1222 ). In one implementation, the economic cost model logic  196  does not generate synthetic GAP change specifiers  185  for GUI objects that have not changed between successive GAP versions ( 1224 ). 
     
       
         
               
             
               
               
             
           
               
                 TABLE 8 
               
               
                   
               
               
                 GUI Element Difference entry for AcadScale 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 &lt;GUIElement Type = “AcadScale Textbox”&gt; 
               
               
                   
                 &lt;Version&gt; 0 
               
               
                   
                  − &lt;GUIElement Alias=“AcadScale”&gt; 
               
               
                   
                   &lt;UniqueID&gt;0xcb&lt;/UniqueID&gt; 
               
               
                   
                   &lt;HWND&gt;0x1a0b3c&lt;/HWND&gt; 
               
               
                   
                   &lt;Location x=“573” y=“790” width=“32” height=“23” /&gt; 
               
               
                   
                   &lt;Class&gt;WindowsForms10.EDIT.app4&lt;/Class&gt; 
               
               
                   
                   &lt;Style&gt;0x560100c0&lt;/Style&gt; 
               
               
                   
                   &lt;ExStyle&gt;0xc0000a00&lt;/ExStyle&gt; 
               
               
                   
                 − &lt;GUIElement Alias=“AcadScale”&gt; 
               
               
                   
                   &lt;UniqueID&gt;0x4&lt;/UniqueID&gt; 
               
               
                   
                  &lt;HWND&gt;0x1a0b3c&lt;/HWND&gt; 
               
               
                   
                   &lt;Location x=“575” y=“792” width=“28” height=“19” /&gt; 
               
               
                   
                  &lt;Class&gt;WindowsForms10.EDIT.app4&lt;/Class&gt; 
               
               
                   
                   &lt;Style&gt;0x560100c0&lt;/Style&gt; 
               
               
                   
                   &lt;ExStyle&gt;0xc0000a00&lt;/ExStyle&gt; 
               
               
                   
                   − &lt;Values&gt; 
               
               
                   
                   &lt;Value SeqNumber=“3” /&gt; 
               
               
                   
                   &lt;/Values&gt; 
               
               
                   
                   &lt;/GUIElement&gt; 
               
               
                   
                  &lt;/GUIElement&gt; 
               
               
                   
                 &lt;/Version&gt; 
               
               
                   
                 &lt;Version&gt; 1 
               
               
                   
                 − &lt;GUIElement Alias=“Academics (1-5)”&gt; 
               
               
                   
                  &lt;UniqueID&gt;0x2ff&lt;/UniqueID&gt; 
               
               
                   
                  &lt;HWND&gt;0x70d0e&lt;/HWND&gt; 
               
               
                   
                  &lt;Location x=“597” y=“388” width=“111” height=“17” /&gt; 
               
               
                   
                  &lt;Class&gt;WindowsForms10.STATIC.app.0.378734a&lt;/Class&gt; 
               
               
                   
                  &lt;Style&gt;0x5600000d&lt;/Style&gt; 
               
               
                   
                  &lt;ExStyle&gt;0xc0000800&lt;/ExStyle&gt; 
               
               
                   
                 − &lt;GUIElement Alias=“Academics (1-5)”&gt; 
               
               
                   
                  &lt;UniqueID&gt;0x308&lt;/UniqueID&gt; 
               
               
                   
                  &lt;HWND&gt;0x70d0e&lt;/HWND&gt; 
               
               
                   
                  &lt;Location x=“597” y=“388” width=“111” height=“17” /&gt; 
               
               
                   
                  &lt;Class&gt;WindowsForms10.STATIC.app.0.378734a&lt;/Class&gt; 
               
               
                   
                  &lt;Style&gt;0x5600000d&lt;/Style&gt; 
               
               
                   
                   &lt;ExStyle&gt;0xc0000800&lt;/ExStyle&gt; 
               
               
                   
                  − &lt;Values&gt; 
               
               
                   
                   &lt;Value SeqNumber=“3”&gt;Academics (1-5)&lt;/Value&gt; 
               
               
                   
                   &lt;/Values&gt; 
               
               
                   
                   &lt;/GUIElement&gt; 
               
               
                   
                  &lt;/GUIElement&gt; 
               
               
                   
                  &lt;/Version&gt; 
               
               
                   
                 &lt;/GUIElement&gt; 
               
               
                   
               
             
          
         
       
     
     Knowing the modification type for a GUI object facilitates the economic cost model logic  196  to determine the appropriate synthetic GAP change specifiers  185  to generate and/or validate received GAP change specifiers  184 . For example, the economic cost model logic  196  may validate GAP change specifiers  184  and/or generate one or more synthetic GAP change specifiers  185  that specify changes to test script statement vectors  816  that attempt to set values in a text box object that has been changed to a read-only combo box. GAP change specifiers  184  and/or synthetic GAP change specifiers  185  may specify that the test script statement vector  816  be modified (transformed) to select values in the combo box using appropriate interfaces rather than attempting to set values in the text box. 
     The economic cost model logic  196  determines whether GUI objects have been removed from a current GAP version  150  and locates the test script statement vectors  816  that reference these removed objects in the current test script  164 . The economic cost engine  182  refers to these statements as first-reference statements (FRS). The variables used in these statements are obtained, and the statements that use the variables whose values are defined in the FRSs are referred to as secondary reference statements (SRS). The economic cost model logic  196  determines whether GUI objects may have been deleted in the subsequent GAP version  152 , and validates received GAP change specifiers  184  and generates one or more corresponding synthetic GAP change specifiers  185  with a wrong path-delete  884 . When a statement of the current test script  164  refers to a variable whose value points to a removed GUI object, the statement of the current test script  826  is considered an SRS. In one implementation, the economic cost engine  182  generates one or more synthetic GAP change specifiers  185  and/or validates received GAP change specifiers  184  corresponding to the identified SRSs. 
     When the values of one or more attributes of a GUI object are modified, a type C modification is performed. FRSs and SRSs are identified for the GUI object with the modified attributes, and corresponding synthetic GAP change specifiers  185  are generated and/or received GAP change specifiers  184  are validated. When the values of GUI objects are added or removed, modifications of the type D occur. After locating FRSs that reference GUI objects whose values have been changed, SRSs are found and the economic engine  182  determines the impact due to the SRSs. When the type of a GUI object is modified then a modification of the type E occurs that involves locating FRSs, checking the new types of the GUI object, invoking corresponding type sub-sumption rules. The economic cost model logic  196  may analyze the modified GUI objects to determine whether to generate synthetic GAP change specifiers  185  with change-element type  884  where GUI objects whose types, properties, or default values are changed in a subsequent GAP version  152 , and/or attempting an operation on a GUI object that does not take into consideration new constraints imposed on the elements of the GUI object. 
     The economic cost model logic  196  analyzes each GUI object referred to in the current test script  164 , the current GAP version  150 , received GAP change specifiers  184 , generated synthetic GAP change specifier  185 , and/or GUI element change status  834 . The economic cost model logic  196  locates, in the economic models  176  repository, the economic model specified by the model specifier  868 , and retrieves a GUI element change cost rule  846  with a change specifier identifier  850  corresponding to the GAP change specifier  184  and/or synthetic GAP change specifier  185 . In one implementation, the economic cost model logic  196  combines one or more attributes of a GUI object (e.g., type and/or class) with the GUI element change status  834 , the model specifier  868 , the wrong path-delete type  880 , wrong path-same type  882  and/or changed element type  884  to form a unique identifier used to locate a corresponding change specifier identifier  850  in the economic model specified by the model specifier  868 . 
     The economic model logic  196  analyzes the GUI element change cost rule  846  components, GAP change specifier  184  and/or synthetic GAP change specifier  185  components, preference identifiers  866  and GUI change efficiency factor  886  to determine whether to adjust the GUI change cost estimate  854 . For example, the economic cost model logic  196  adjusts the GUI change cost estimate  854  based on whether the skills coefficients  872 , complexity identify  874 , quality identifier  876 , system resource utilization identifiers  852 , quality ranking  860 , and/or complexity ranking  862  are within an acceptable variance as specified by the preference identifiers  866 . The economic cost model logic  196  obtains the GUI transformation cost  848  based on the adjusted GUI change cost estimate  854 . In other words, the GUI change cost estimate  854  is adjusted to obtain the GUI transformation cost for the GAP change specifier  184  and/or synthetic GAP change specifier  185 . The economic cost model logic  196  processes each received GAP change specifier  184  and/or generated synthetic GAP change specifier  185  to obtain the corresponding GUI transformation costs  848  and generates the test script transformation cost report  186  with the GUI transformation costs  848 . 
       FIG. 13  shows a flow diagram for outputting a test script transformation cost report  186  based on a GUI difference model  162 . The economic cost engine  182  receives the GUI difference model  162  and GUI element metadata  140  ( 1304 ). The economic cost engine  182  receives a current test script representation  814  that includes a test script statement vector  816  ( 1306 ). The script parser logic  812  parses the test script statement vector  816  into vector nodes to determine the GUI objects to which the test script statement vector  816  navigates ( 1308 ). The economic cost engine  182  invokes the OR lookup logic  172  for each GUI object identified by the test script statement vector  816  to retrieve the properties of the GUI objects from the object repository  174  ( 1310 ). The path traversal logic  824  analyzes the navigation path of the GUI element difference entries  810  that correspond to the GUI objects identified by the test script statement vector  816  ( 1312 ). The economic cost model logic  196  validates a GAP change specifier  184  and/or determines the type of synthetic GAP change specifier  185  to generate ( 1314 ). The economic cost model logic  196  generates a synthetic GAP change specifier  185  corresponding to the type of GUI element change identified by analyzing the current test script  164 , current GAP version  150  (e.g., current GAP tree model) and GUI difference model  162  ( 1316 ). The economic cost model logic  196  locates, in the economic model specified by the model specifier  868 , the GUI element change cost rule  846  corresponding to the GAP change specifier  184  and/or synthetic GAP change specifier  185  and applies the GUI element change cost rule  846  to obtain the GUI transformation cost  848  ( 1318 ). The economic cost model logic  196  generates the test script transformation cost report  186  based on the GUI transformation cost  848  ( 1320 ). 
     In one implementation, the economic cost engine architecture  110  uses adaptive programming including class and object graphs and an abstraction that treats all objects uniformly. The path traversal logic  824  and the economic cost model logic  196  may distinguish complex and simple types of GUI objects. Complex types contain fields while simple types do not. Let T be finite sets of type names and F of field names or labels, and two distinct symbols this ∈ F and ⋄ ∈ F. Type graphs are directed graphs G=(V, E, L) such that: 
     V ⊂ T, the nodes are type names; 
     L ⊂ F, edges are labeled by field names, or “⋄” where fields do not have names. Edges that are labeled by “⋄” are called aggregation edges, and edges that are labeled by field names reference edges. The difference between aggregation and reference edges becomes clear with the following example. Fields of classes in object-oriented languages designate instances of some classes, and these fields have names that are used to reference the fields. Each field of a class is defined by the name of the field and the name of the class (type) that this field is an instance of. The name of a field is the label of the corresponding reference edge in the type graph. 
     When a class designates a GUI object o k  and the other class designates a GUI object o n  that is contained in the object o k , the type graph has two nodes, one for the object o k  and the other for the object o n  that the object o k  contains. The names of the corresponding classes serve as their types. The relation between two nameless objects is represented using the edge labeled with the “⋄” in the type graph. 
     E ⊂ L×V×V, edges are cross-products of labels and nodes; 
     for each v ∈ V, the labels of all outgoing edges with the exception of “⋄” are distinct; 
     for each v ∈ V, where v represents a concrete type, 
     
       
                 
         
             
             
         
      
     
     An object graph is a labeled directed graph O=(V′, E′, L′) that is an instance of a type graph G=(V, E, L) under a given function Class that maps objects to their classes, if the following conditions are satisfied: 
     for all objects o ∈ V′, o is an instance of the concrete type given by function Class(o); 
     for each object o ∈ V′, the labels of its outgoing reference edges are exactly those of the set of labels of references of Class(o) including edges and their labels inherited from parent classes; 
     for each edge 
                                
Class(o) has a reference edge
 
                                
such that v is a parent type of Class(o) and u is a parent type of Class(o′).
 
     An object graph is a model of the objects, represented in GAPs, and their references to each other. A collection of fields in an object graph is a set of edges labeled by field names. A collection of aggregated objects in an object graph is a set of edges labeled by “⋄”. A path in a type graph G=(V, E, L) is a sequence of nodes and labels p G =(v 0 e 1 ,v 1 e 2 , . . . e n v n ), where v i ∈ V and 
                                
for 0≦i≦n. A concrete path is defined as an alternating sequence of type names and labels designating reference edges. In general a concrete path p c  is a subset of the corresponding type path p G , i.e. p c   ⊂ p G .
 
     An object graph has the special object o r ∈ V′, Or is a collection of root objects o r   ⊂ V′ in the object graph O given by function root: O→o r . This object has type Class(o r )=root and its relation with objects in its collection is expressed via o r →⋄→o′∈ E′. 
     Given an object o of some type the traversal logic  824  and the economic cost model logic  196  work together to identify one or more reachable objects that satisfy certain criteria. The task performed is equivalent to determining whether test script statement vectors  816  that describe navigation paths are valid. Navigation paths specified in test script statement vectors  816  can be thought of as specification of constraints for the object reach-ability problem. Finding reachable objects is done via traversals. The traversal of an edge labeled e corresponds to retrieving the value of the e field. Every edge in the object graph is an image of a has-part edge in the type graph: there is an edge e(o 1 , o 2 ) in O only when there exist types v 1  and v 2  such that object o 1   is of type v 1 , v 1  has an e-part of type v 2 , and o 2  is of type v 2 . 
     The first node of a path p is called the source of p and the last node is called the destination of p. A traversal of an object graph O started with an object v i  and guided by paths from a set of paths p is done by performing depth-first search on O with p used to prune the search. The resulting traversal history is a depth-first traversal of the object graph along object paths agreeing with the given concrete path set. 
     The problem of identifying all reachable objects from a given object o that satisfy certain criteria is formalized as follows. For each pair of classes c and c′, a set of edges e may be identified by computing FIRST(c, c′) if it is possible for an object of type c to reach an object of type c′ by a path beginning with an edge e. More precisely, FIRST(c, c′)=e ∈ E, such that there exists an object graph O of C and objects o and o′ such that: 1) Class(o)=c; 2) Class(o′)=c′; and 3) o e*o′. 
     The last condition, o e* o′ indicates that there is (           ) a path from o to o′ in the object graph, consisting of an edge labeled e, followed by any sequence of edges in the graph. The lack of information about the actual graph is represented by the existential operator          .
     The task of static checking of test scripts (e.g., transformed test scripts  178 ) is greatly simplified when the names of foreign components names are defined as string constants. When the names of GUI objects are specified using expressions, the values of these expressions may not be determined until run-time. Type graphs facilitate the economic engine system  800  to infer types of expressions and variables that hold the names of GUI objects. The economic engine system  800  applies concepts based on the Traversal Graph Analysis (TGA) defined in adaptive programming to infer types of expressions and variables. 
     An adaptive strategy S=(R, π, δ) represents paths in an object graph, where R={s, d}, where s and d are the source and destination GUI objects of a path in an object graph, and R ⊂ O, where O is the set of objects in a type graph, π={e, α}, where e is a set of fields and α is a set of variables that designate a set of some edges α ⊂ e, and δ=            is a set of transition edges representing objects and attributes respectively. Each element in a strategy S is either the name of some object or a variable designating an object and/or attributes.
     The expression π(o, o′) designates a set of objects {o′}, such that each object o′ of the set is a part of the object o expressed by some edge e ∈ π such that e(o, o′). For example, test script statements may be considered strategies that define strategy graph edges a           b and a         b for test script statements Window(“a”).VBWindow(“b”) and Window(“a”).VBWindow(“b”).property(“ReadOnly”), respectively. Thus, a strategy is an abstraction of test script statements, as well as an abstraction of a set of paths in a type graph.
     For example, a type graph of an organizational structure of a company may include: a CEO as a root type of some GUI object that contains the GUI object stock of type integer and aggregates type CTO. CTO is a type that has GUI objects salary of type Check and boss of type CEO. Type Check has in turn fields amount of type float and issuer of type CEO. A strategy CEO           α1         α2          amount for the test script statement:
     Window(“CEO”).Window(strex1).Window(strexp2).property(“amount”) for the type graph described above designates strategy S, where s=CEO, d=amount, α1 is a variable designating objects computed via string expression strexp1, and α2 is a variable designating attribute object computed via string expression strexp2. Computing π(CEO, o′) the type {CTO} is obtained, and computing π(CTO, o′) the types {CEO,check} are obtained. 
     Each node in a strategy is assigned a distinct sequence number, and nodes are expressed as pairs (i, π). Given functions Δi: N×N→δ and Δπ: π×π→δ and two sequential natural numbers k and k+1, the function Δi computes the transition edge between nodes that are assigned these numbers in S, and Ø if there is no transition edge. Correspondingly, given two nodes π q  and π r  in some type graph, function Δπ computes the transition edge between nodes, and Ø if there is no transition edge. 
     When the values of string expressions in test scripts statements cannot be computed until run-time, the string expressions may be inferred. The path traversal logic  824  and the economic cost model logic  196  work together to analyze test script statements vectors  816 , using type graphs by transforming test script statements vectors  816  into an adaptive strategy with variables replacing string expressions. The economic cost model logic  196  computes possible values for each variable and generates traversal paths for each strategy. Where at least one path is identified, then a corresponding GAP change specifier  184  is validated and/or a synthetic GAP change specifier  185  is generated, since values of expressions that compute names of objects may not be in the computed paths. 
     The path traversal logic  824  identifies one or more possible paths, while the economic cost model logic  196  validates paths for the expressions and statements. The economic cost model logic  196  computes the set of edges e for each pair of classes c and c′, by computing FIRST(c, c′) where an object of type c exists that can reach an object of type c′ by a path beginning with an edge e. Recall from above that FIRST(c, c′)=e ∈ E, such that there exists an object graph O of C and objects o and o′ such that: 1) Class(o)=c; 2) Class(o′)=c′; and 3) o e* o′. 
     The last condition, o e* o′ says that there is (           ) a path from o to o′ in the object graph, consisting of an edge labeled e, followed by any sequence of edges in the graph. In one implementation, the method FIRST is implemented using two sets of logic: path traversal logic  824  and GUI class rules logic  828 .
     The path traversal logic  824  takes the set R of source and destination components in S and set π as input parameters. The path traversal logic  824  outputs a tree of valid paths in a type graph that satisfy a given strategy. Some of the input components may not make it into the path tree because they do not start any valid paths. 
     In one implementation, the path traversal logic  824  invokes the economic cost model logic  196 , which in turn recursively calls itself. The economic cost model logic  196  uses three parameters: a component o that is a potential current node in the path, sequence number i of the node in the strategy S, and the transition edge δ between nodes in S that are assigned two sequential natural numbers i and i+1. The goal of the GUI class rules logic  828  is to color the potential current node o in the path as either red or blue. Where colored red object o is considered a dead end on the path in the type graph that does not lead to the designated destination nodes. Otherwise, the node is colored blue and this color is propagated up to the source nodes which are subsequently included in the path tree. 
     The economic cost model logic  196  completes when the sequence number i is equal to or the greater of the number of nodes in the strategy, |π|, and/or where there is no transition edge from the current node. When the economic cost model logic  196  completes, the economic cost model logic  196  colors the current node blue. In the calling procedure the color of the node is checked, and where the node is blue, then node is attached to its parent node in the path tree. 
     In one implementation, the economic cost model logic  196  computes the set of edges e for each pair of classes c and c′, where an object of type c is identified that can reach an object of type c′ by a path beginning with an edge e. The logic is applied individually to each test script statement vector  816  in which foreign GAP objects are specified using string expressions whose values are not known before the current test script  164  is executed. The economic cost model logic  196  infers possible names of foreign objects that string expressions may evaluate to at runtime. 
     
       
         
               
             
               
               
             
           
               
                 TABLE 9 
               
               
                   
               
               
                 Path Traversal and GUI class rules logic 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                  Path traversal logic (R ε S, π ε S) 
               
               
                   
                 for all s ε R do 
               
               
                   
                  economic cost model logic (s, 0, Δi(0,1)) 
               
               
                   
                  if color(s) = red then 
               
               
                   
                  remove s from R 
               
               
                   
                  end if 
               
               
                   
                 end for 
               
               
                   
                 economic cost model logic (o ε O, i ε N,             ε δ) 
               
               
                   
                 if i ≧|π| or            = Ø then 
               
               
                   
                  color(o)            blue 
               
               
                   
                 else 
               
               
                   
                  for all o′ ε πi(o, o′) do 
               
               
                   
                  if Δπ(o,o′) =            then 
               
               
                   
                   economic cost model logic (o′, i + 1, Δi(i, i + 1)) 
               
               
                   
                   if color(o′) = blue then 
               
               
                   
                   AddChildToTree(o, o′) 
               
               
                   
                   end if 
               
               
                   
                  end if 
               
               
                   
                  end for 
               
               
                   
                  if children(o) = Ø then 
               
               
                   
                  color(o)            red 
               
               
                   
                  else 
               
               
                   
                  color(o)            blue 
               
               
                   
                  end if 
               
               
                   
                 end if 
               
               
                   
               
             
          
         
       
     
     Often the same string expressions are used in different statements in the same scripting scope. The same expressions compute the same values, where the expressions are located in the same scope, provided that the values of the variables used in these expressions are not changed. Using program analysis techniques the path traversal logic  824 , and the economic cost model logic  196  work together to detect expressions at compile time whose variables are not changed at run-time. The path traversal logic  824  identifies one or more possible names of foreign GUI objects that may be substituted for string expressions in test script statements. While the economic cost model logic  196  identifies from among the possible names of foreign GUI objects, valid GUI objects. Given the same expression used in different test script statements in the same script scope, and provided that the values of the variables used in these expressions are not changed by other expressions executed between these statements, the economic cost model logic  196  identifies a set of names of foreign GUI objects computed by these string expressions. This set of GUI objects is obtained by taking the intersection of the sets of names computed by the path traversal logic  824 . 
     For example, consider the strategy graph S 1  CEO           α1         α2          amount for the type graph for the test script statement expression: Window(“CEO”).Window(strexp1).Window(strexp2).property(“amount”). The economic cost model logic  196  computes values for type scheme variables α1={CTO} and α2={boss, salary}.
     Suppose a different strategy graph S 2  exists, where Programmer           α2         bonus for y[“Programmer”][strexp2].attribute(“bonus”) for some other type graph. Notice that the string expression variable strexp2 is the same in both statements, and because of that the string expression variable strexp2 is designated by the same type scheme variables in both the strategy graphs. Suppose that by applying the path traversal logic  824  that values for type scheme variable α2={salary} are computed. In one implementation, in order to determine the value of variable α2 that satisfies both S 1  and S 2 , the economic cost model logic  196  identifies the intersection of the sets of values of α2 computed for these two strategies. The resulting set α2={salary} is the result of pruning the navigation paths.
     This example illustrates the idea of pruning navigation paths using context-sensitive dataflow analysis that may be used by the economic cost model logic  196 . By determining definitions and uses of a variable that designate names of GUI objects in a given scope, sets of values are computed for each transformed test script statement in which a variable is used. Then the intersection of these sets is taken to determine common values that this variable can take in the scope considered. 
     The economic engine system  800  provides modularization integrity as a mechanism for ensuring the validity of GAP change specifiers  184  and/or synthetic GAP change specifiers  185 . Modularization integrity specifies that each current test script statement identified by a GAP change specifier  184  and/or a synthetic GAP change specifier  185  to be changed may only communicate directly with the objects that belong to GUIs for which the current test script statement, as changed by the GAP change specifier  184  and/or a synthetic GAP change specifier  185 , is created. Compositions of current test script statements changed as specified by GAP change specifiers  184  and/or synthetic GAP change specifiers  185 , in which GUI objects are accessed by calling functions exported by the current test script statements changed as specified, should not violate modularization integrity. The economic engine system  800  ensures the modularization integrity of GAP change specifiers  184  and/or synthetic GAP change specifiers  185  by analyzing compositions of current test script statements changed as specified by GAP change specifiers  184  and/or synthetic GAP change specifiers  185  to build the transitive relations between the current test script  164  and the current test script  164  changed as specified by the GAP change specifiers  184  and/or synthetic GAP change specifiers  185 . 
     For example, a statement Func(“y”, “z”), found in a suite of related test scripts, navigates to the field z of foreign GUI object y in some test scripts that export function Func. Thus, the some test scripts in the suite of related test scripts may violate the modularization integrity by implicitly interoperating the test scripts via the function Func even though this communication may be prohibited by the constraints of a given test suite. In one implementation, the economic engine system  800  encodes modularization constraints when defining test scripts using the keyword constraints as part of a global comment in each test script. These constraints define GAPs and their GUI screens as well as other test scripts with which a given test script may communicate. An example is a statement that specifies a constraint is constraints screen(“Q”) test_scripts(“P, S”). This constraint effectively prohibits a given test script from communicating with other GAPs, GUI screens, and test scripts, except the screen Q and test scripts P and S, explicitly or implicitly. 
     The time complexity of the path traversal logic  824  and the economic cost model logic  196  is exponential to the size of the type graph for each test script  164 . Because the path traversal logic  824  and the economic cost model logic  196  involve the search of one or more nodes and edges in the type graph that contains cycles for each node in the strategy, the time complexity is O((V+E) max(|π|) ) where V is the number of nodes, E is the number of edges in the type graph, and max(|π|) is the maximum number of nodes in strategies. The operations of storing successors in the table of variables take O(1). In general, the number of nodes max(|π|) in strategies is much smaller than the number of nodes in type graphs. All graph nodes may not need to be explored for each node in a strategy. 
     The systems may be implemented in many different ways. For example, although some features are shown stored in computer-readable memories (e.g., as logic implemented as computer-executable instructions or as data structures in memory), all or part of the systems, logic, and data structures may be stored on, distributed across, or read from other machine-readable media. The media may include hard disks, floppy disks, CD-ROMs, a signal, such as a signal received from a network or partitioned into sections and received in multiple packets communicated across a network. The systems may be implemented in software, hardware, or a combination of software and hardware. 
     Furthermore, the systems may be implemented with additional, different, or fewer components. As one example, a processor or any other logic may be implemented with a microprocessor, a microcontroller, a DSP, an application specific integrated circuit (ASIC), program instructions, discrete analog or digital logic, or a combination of other types of circuits or logic. As another example, memories may be DRAM, SRAM, Flash or any other type of memory. The systems may be distributed among multiple components, such as among multiple processors and memories, optionally including multiple distributed processing systems. Logic, such as programs or circuitry, may be combined or split among multiple programs, distributed across several memories and processors, and may be implemented in or as a function library, such as a dynamic link library (DLL) or other shared library. 
     While various embodiments have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.