PATENT ABSTRACT
A computer program product embodied in a computer-readable medium is configurable to accomplish execution of an application that is specified and encoded in a markup-based descriptor language. The product includes client runtime computer code configured to cause a client computer device to process the markup-based descriptor language to deploy an application to accomplish execution of the application. The client runtime computer code is further configured to process the markup-based descriptor language to selectively configure the client computer device to deploy the application so as to accomplish execution of the application by the client computer device stand-alone or by the client computer device in cooperation with a server to which the device is connectable via a network connection.

PATENT DESCRIPTION
TECHNICAL FIELD OF THE INVENTION  
       [0001]     The present invention is in the field of developing and deploying applications and services for a full range of devices, scaling from mobile phones to computer desktops, within a flexible markup based distributed architecture.  
       BACKGROUND OF THE INVENTION  
       [0002]     As wireless computing devices become more ubiquitous, the demand for value-added mobile applications and solutions to deliver these applications increases. Enterprises expect new mobile applications to seamlessly integrate with the existing corporate information system, thus granting access to existing resources and services to highly mobile workers. Examples include accessing legacy applications and connecting to enterprise databases through wireless devices.  
         [0003]     Mobile applications may have challenges such as: 
        Accessing a mobile application from different kinds of devices, for example from a PDA or a desktop computer, depending on the location of the user. PDAs and desktops differ in several ways, including form factors, operating systems and connectivity.     Running a mobile application on a mobile device continuing to work offline, in the case of a broken connection. An offline behavior utilizes access to local resources.     A mobile application accessing services published by some Web Services provider implementing Web Services standards, including SOAP, WSDL and UDDI.        
 
         [0007]     Deploying mobile applications in such heterogeneous environments greatly increases the complexity of the solutions, and presents many unresolved challenges. These challenges in turn affect the development of applications, as well as ongoing maintenance. Some issues to address are: 
        Open standards compatibility. Proprietary solutions are unlikely to be practical in such heterogeneous environments. The solution should fit the emerging Web Services standards, including SOAP, WSDL and UDDI.     Multi-platform deployment. The same service may be accessed from different kinds of devices and different communication protocols may be used.     Ease of modification. Since the markets change quickly, especially emerging markets like the wireless applications market, it is desirable that smart applications are easy and quick to modify.     Adaptable deployment. No single deployment model fits all contexts. The suitable deployment model depends on several factors, such as device resources, security requirements and application characteristics. Deployment models typically range from a thin client connected to a server, to a stand-alone running application.     Access to local resources. Mobile devices cannot rely exclusively upon server side resources, since the connection with a server cannot always be guaranteed. Furthermore, it can be costly to continually maintain a connection to a server when it is only occasionally required.     Enhanced user interface. Required to improve the user experience.        
 
         [0014]     Solutions like HyperText Markup Language (HTML) combined with HyperText Transfer Protocol (HTTP), Wireless Application Protocol (WAP), pure Java programming, Application Servers, and proprietary Software Development Kits (SDKs), each address a subset of these challenges, but more comprehensive solutions are desired.  
         [0015]     HTML and WAP are open standards and may be deployed on multiple platforms. Services developed with these standards may be easily modified, since they become immediately available to the client devices when deployed on the server. Unfortunately, the deployment model of HTML and WAP is a rather rigid thin client model and a connection to a server must remain typically available during the execution of the application. This may be costly and even impractical, should the connection to the server be interrupted unexpectedly. Another drawback is that these solutions allow little access, if any, to local resources. Finally, the user interface is rather modest, at best.  
         [0016]     Another solution mentioned above is pure Java programming. Although Java is quite portable, and is considered to some extent as an “open standard”, there are in fact multiple Java standards, including J2ME MIDP, Personal Java, and Java 2 Standard Edition. Thus, deploying a Java application on different platforms may require rewriting it several times, which implies involving highly-skilled developers. The same problem arises when modifying an application. Java provides good means of implementing a deployment model targeted to a specific architecture, accessing local resources and providing effective User Interfaces. Unfortunately, each deployment model generally requires a specific Java program, thus making it unfeasible to dynamically adapt a given application to new architectural requirements.  
         [0017]     Proprietary SDK&#39;s provided by mobile device manufacturers are quite comparable in capabilities and drawbacks to the Java programming approach, but have the additional drawback of not being open standards. The use of such proprietary solutions entails a commitment to one particular (inflexible) solution, which in turn restricts the ability to later port an application to other mobile devices. Should the chosen solution at some point no longer meet the requirements of the user, it could be extremely costly to implement a completely new solution.  
         [0018]     Application servers, and especially Java application servers based on the Java 2 Enterprise Edition (J2EE) standard, promote several architecturally significant separations of concerns. One architectural feature is a variation on the HTML approach, namely Java Server Pages (JSP). JSPs are targeted to improve the separation between interaction logic and business logic on the server side, but have the same limitations as traditional HTML architectures on the client side. Another architectural feature is the distinction between the development phase and the deployment phase for an application, thus allowing some flexibility for adapting to the underlying technical architecture. However, the deployment process is typically only concerned about server-side deployment characteristics, including transactions, security and database access. The distribution of processing and resources between the client and the server are not addressed by this solution.  
       SUMMARY OF THE INVENTION  
       [0019]     A computer program product embodied in a computer-readable medium is configurable to accomplish execution of an application that is specified and encoded in a markup-based descriptor language. The product includes client runtime computer code configured to cause a client computer device to process the markup-based descriptor language to deploy an application to accomplish execution of the application. The client runtime computer code is further configured to process the markup-based descriptor language to selectively configure the client computer device to deploy the application so as to accomplish execution of the application by the client computer device stand-alone or by the client computer device in cooperation with a server to which the device is connectable via a network connection.  
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0020]      FIG. 1  illustrates an outline of the runtime architecture, in accordance with an embodiment of the present invention.  
         [0021]      FIG. 2  illustrates an outline of the development and deployment process, in accordance with an embodiment of the present invention.  
         [0022]      FIG. 3  illustrates the processing runtime client and server stacks, in accordance with an embodiment of the present invention.  
         [0023]      FIG. 4  illustrates a description of three major deployment profiles supported by preferred embodiments of the present invention.  
         [0024]      FIG. 5  illustrates the flow of information within the client and server stacks of an embodiment of the present invention, for the thin connected profile.  
         [0025]      FIG. 6  illustrates the flow of information within the client and server stacks of an embodiment of the present invention, for the thick connected profile.  
         [0026]      FIG. 7  illustrates the flow of information within the client stack of an embodiment of the present invention, for the stand-alone profile.  
         [0027]      FIG. 8  illustrates the flow of information within the client and server stacks of an embodiment of the present invention, for the applet profile.  
         [0028]      FIG. 9  illustrates an embodiment of a visual design module of the present invention  
         [0029]      FIG. 10  illustrates embodiments of the markup based descriptors and corresponding screens displayed by embodiments of the present invention  
     
    
     DETAILED DESCRIPTION  
       [0030]     A comprehensive flexible solution, based on a markup language like XML, for developing smart mobile applications and services, and for deploying them in heterogeneous environments. Smart mobile applications can be used in a connected or disconnected mode and they can access and process resources locally or on a server. According to one aspect, a flexible client-server architecture is targeted to run smart mobile applications. The applications and the deployment architecture are specified within markup-based descriptors. The supported architecture specifications range from a standalone client running an entire unconnected application, to a thin client managing the User Interface with the business logic of the application running on the server. In between, many combinations of client and server side processing may be specified. The characteristics of the architecture may be dynamically modified, thus leading to increased flexibility in the deployment. Mostly, the markup-based descriptors are forms specifying the User Interface of the application, the behavior of the application in response to the interactive events, the business logic of the application, and the location where the resources are to be found and processed. The behavior of the application is defined in a scripting language, which is given access to the resources of the device, including access to methods written in a language like Java, either on the client or on the server.  
         [0031]     For example, a client runtime system displays interactive screens, or forms, interacting with specific server components running within an application server. The client runtime retrieves a form specification, either locally or from the server. When the form is accessed from the server, it may be preprocessed therein. Otherwise, it is preprocessed on the client. The preprocessing of a form specification is a construction process, where the actual form to be displayed is constructed as specified in the form specification, possibly using available resources like databases to populate the actual form. The client runtime parses and processes the actual form to generate the User Interface on the device, and then handles the interactive events. The client runtime is typically installed on the computing client device, which may be a smart phone, a PDA, or a desktop computer, but it can also be downloaded on demand as an applet into a browser. The server software is typically installed on a server running a Java application server. The entry point in the server software is a servlet using an XML configuration file generated by the Designer. When a client device sends a request, the servlet analyzes the request, prepares the XML formatted response, and sends it back to the client. The preparation process may include preprocessing of a form specification, and retrieval of deployed forms and/or data from backend systems.  
         [0032]     According to another aspect, a development and a deployment process is provided for smart applications and services. For example, the development and deployment process may be performed in three steps. The first step is the user interface and interaction design step, and produces the interactive specification of the forms. Within this step, databases and other resources are managed and accessed as abstract references, without any indication about their physical location or other implementation-dependent characteristics. The second step is the deployment definition step, that is, defining where and how the form specifications, resources and data are to be deployed on the client and the servers. The third step corresponds to the actual deployment on the target platforms. This separation provides means for deploying the same application across multiple kinds of distributed environments. The environments may differ by the operating system of the client device, by the resources available on the client or on the server, and by the characteristics of the connection. The result of the development and the deployment process is a set of markup documents describing the architecture and the behavior of the resulting application.  
         [0033]     As an example of this development and deployment process, an easy-to-use Rapid Application Development (RAD) designer tool may be provided for application developers. The designer tool running on the developer&#39;s computing device provides the developer with tools for each step of the development and deployment process, from the visual definition of screens to the testing of full-fledged client-server applications. With the designer tool, the developer can define and edit the screen visually. The designer tool creates the XML files required by the client and by the server.  
         [0034]     The same application may thus be deployed on different deployment models and platforms, providing increased flexibility (useful, for example, for wireless implementations). For example, if the application is designed to support the sale force of a large corporation equipped with both wireless PDAs and desktop computers, different types of deployments may be required. In the office, the user may expect to access the application through a thick connected model, using the full processing power of a desktop computer and the high bandwidth of the local network. While outside the office, the user may access the application, for instance to check the status of an order, from either a PDA using a thin connected model or from a browser through the Internet by using an applet deployment mode. When a connection is not available, the application may operate in a stand-alone mode, thus allowing the user to enter an uncommitted order or estimate a total price.  
         [0035]      FIG. 1  illustrates, at a broad level, the runtime architecture of one embodiment in accordance with the present invention. The runtime architecture is implemented on a computing client device  102  and a server  100 , connected through a connection link  117 . The illustrated embodiment corresponds to a “thin client” runtime configuration.  
         [0036]     The computing client device  102  may include two or more layers. The operating system  110  interfaces to the hardware and handles the low level management of the resources on the device, such as memory, storage, and user input. A Java Virtual Machine is considered an extension of the operating system, abstracting the device&#39;s resources into the Java standard, and providing a standard programming platform across devices. A third layer is the client runtime  112 , providing part of the client side functionality. The server  100  may comprise a Java J2EE compatible application server  108 , which manages the services available on the server. The server runtime  106  based on a Java servlet provides part of the server side functionality in accordance to the present invention. The communication link  117  may be an Internet connection based on the HTTP protocol.  
         [0037]     When, through an interaction  101  with the computing client device  102 , a user requests access to a form from a service located on the server  100 , the client runtime  112  sends a request  107  to the server  100  using the available communication link and protocol  117 . On the server  100 , the application server  108  analyzes the request and forwards it to the server runtime  106 . The server runtime processes the request, recognizes it as a form request, retrieves the requested form specification stored in an XML file  116  and additional data from external resources  118  as appropriate, and combines them to construct the preprocessed XML form  120 , which is passed back to the client device  102 . The client runtime  112  then processes the XML form and generates  103  the corresponding User Interface on the device&#39;s display.  
         [0038]     This general architecture described with reference to  FIG. 1  illustrates a deployment with a thin client profile where the construction of the form occurs on the server and no local storage is used on the client. However, other deployment profiles may be employed. The following deployment profiles will be later discussed in more detail: 
        Stand-alone: the form specifications are stored, and the displayable interactive forms constructed and processed on the client, and no connection to a server is utilized.     Thick connected client: the form specifications are retrieved from a server, but the displayable interactive forms are constructed and processed on the client. Local resources, such as local databases may be involved.     Thin Client: the form specifications are stored on the server. The displayable interactive forms are constructed on the server and the preprocessed forms are then passed to the client. The client handles the processing of the events once the form is on the device, and no access to client resources is utilized.     Applet deployment: the runtime is not installed on the client; it is downloaded on request from the server and runs inside a browser.        
 
         [0043]     The named deployment profiles are not fixed during the execution of a given application. For example, the frequently used forms of an application may run in a stand-alone mode, and the less frequently used ones may be deployed in a thin or thick client mode. Furthermore, the present invention provides means for dynamically changing the deployment profile during the execution of an application, thus leading to highly flexible architectures.  
         [0044]      FIG. 2  illustrates, at a broad level, an embodiment of the development and deployment process in accordance with the present invention. A Rapid Application Development (RAD) designer tool  200  running on the developer&#39;s computing device is provided. The designer tool  200  comprises three modules: the visual design module  226 , the deployment module  228 , and the test module  244 . The process is carried out in four major steps: the visual design step  202 , the deployment definition step  206 , the export deployment step  210 , and the test platform step  240 .  
         [0045]     The visual design step  202  includes defining the abstract form specifications  204  of the application. An abstract form specification is stored as an XML document. The developer designs the visual aspect of the application&#39;s forms, by interacting with the visual design module  226 , typically by positioning visual components on the screen. The developer may specify the interactive behavior of each visual component through script code, as required. Capability is provided for script code to access external resources as abstract references, delaying the binding to the actual resources until the deployment definition step  206 . As a result, the visual layout and behavior of the applications are specified independently of the target platforms. External resources the script code can manipulate include Java methods, images and databases. While presenting the visual aspect of a form, the designer tool  200  generates an XML representation  204  containing the full specification of the abstract form, including the interactive behavior of the form. The developer may choose to perform part or all of the tasks of the visual design step  202  by directly editing this file, using the text-editing feature of the visual design module  226 .  
         [0046]     During the deployment definition step  206 , the developer defines one or more deployment targets  230  for the current application using the deployment module  228 . The characteristics of the deployments for an application are stored in an XML document, namely the project file  208 . Each deployment target  230  corresponds to a specific platform  242 , and comprises the description of the client profile and the accessed servers. For each abstract resource referenced during the visual design step  202 , the developer specifies its actual location and settings.  
         [0047]     During the export deployment step  210 , the developer actually deploys the required files on the client device  238  and the server  236 , using the deployment module  228  of the designer tool  200 . When the developer requests the deployment module  228  to export the deployment, the designer tool  200  creates all the files required by the deployment and copies the files and the resources either to the client or to the server according to the deployment definition.  
         [0048]     During the test platform step  240 , the developer tests the application in the context of each of the platforms  242  defined during the previous development steps, using the test module  244 .  
         [0049]      FIG. 3  illustrates the client and server processing runtime stacks of various architecture embodiments. The processing stack comprises three principal layers: the resource manager  320 , the processor  306 , and the User Interface (UI) Manager  300 . Two types of stacks are defined: the client stack  308 , which includes the three layers named above, and the server stack  318  which excludes the UI Manager  300 . By providing similar processing stacks on the client device  326  and on the server  328 , improved flexibility in the deployment of applications, is provided since most of the applications&#39; logic may be run uniformly on either the client or on the server.  
         [0050]     Within the processor  306 , the form builder  314  handles the transformation of form specifications into displayable interactive forms. The form builder  314  analyzes the form specification to check if additional resources are required, including data, image or methods. The requests for the resources are passed to the resources manager  320 , as needed. For example, the form specification may specify that a visual grid be filled with data extracted from a database table. The form builder  314  is in charge of performing this task. The developer may use script code within the form specification to define how the form may be constructed, making the construction process more flexible. If the form contains script code, the script engine  316  compiles it.  
         [0051]     The UI Manager  300  interacts with the input and output capabilities of the client device  326 , such as screen, keyboard, touch screen, sound card or mouse. These elements are specific to the device and are managed by the operating system of the device. The display manager  302  handles the creation of the visual layout of the forms, using the visual controls available on the client device, such as buttons, text fields or grids, as expressed in the displayable interactive form created by the form builder  314 . When interest for an event has been registered within a form, the event manager  304  is in charge of notifying the corresponding component of the form whenever the event occurs, and if script code has been associated with the event on the component, the script engine  316  is in charge of running the corresponding code.  
         [0052]     The resource manager  320  receives the requests for external resources, either from the processor  306  or from the event manager  304 . The resource manager  320  includes connectors  324  to access the different types of resources. Available resources include, for example: 
        Databases 
            Table: a table from a database, such as JDBC and XML databases     Query: an SQL query on a JDBC database or an XML query to an XML file    
            Multimedia 
            Image file: a file containing an image     Multimedia stream: a link to a video or sound streaming server or to a file containing video or sound data     Graphics    
            Network Files 
            XML file: an XML document stored as a file, which is parsed into a Document Object Model (DOM) tree    
            Methods 
            A Java class: a user defined class implementing some complex business logic    
            EJB: Entreprise Java Beans     File System: access to the local storage     Other Device Resources 
            Device specific resource (IrDA, bar code)    
            Functional Resources 
            Payment: secure payment     Identification: secure identification     Location service: a service providing the geographical location of the device    
               
 
         [0072]     When the returned resource is an XML document, the resource manager  320  parses the XML file and returns the DOM representation of the XML document.  
         [0073]     The requester  310  handles the communications between the client and the server. The exchange of data is structured essentially in the form of XML messages, either in a text format or a compiled format. The compiled format is managed by the compiled XML module  312 , and is more efficient, as the size of the transferred data is reduced. Additionally, it saves the trouble of translating objects into XML on the server and the reverse on the client.  
         [0074]      FIG. 4  shows a broad description of the three primary deployment profiles. Each of these profiles will be later described in a more detailed fashion, in  FIGS. 5, 6 ,  7 . An additional specific profile, namely the applet profile, represents an example of a mix of the three primary profiles, and is illustrated in  FIG. 8 : 
        Thin Connected Client  404 : On the server  408 , the resource manager retrieves the deployed form from the server storage. The processor on the server  408  retrieves additional resources, if necessary, and processes the form. The processor then sends the processed form to the UI manager on the client device  406 , which generates the interface on the device&#39;s display.     Thick connected client  402 : On the server  408 , the resource manager retrieves the form specification from the server storage and sends the form specification to the processor on the client device  406 . On the client device  406 , the processor retrieves additional resources if necessary, processes the form specification and passes the processed form to the UI manager, which generates the interface on the device&#39;s display.     Stand-alone  400 : On the client device  406 , the resource manager retrieves the form specification from the local storage resource and passes the form specification to the processor. The processor retrieves additional resources if necessary, processes the form specification and passes the processed form to the UI manager, which generates the interface on the device&#39;s display.          
         [0078]     In each of these modes, including the stand-alone mode, external data can be incorporated through a connector to an external resource. For example, the client device  406  may query a network database or an XML data server on the web.  
         [0079]     An additional mode, the applet deployment mode, can be thought of as a combination of the thin and the thick connected client profiles. However, in this case, the client runtime is not an application but an applet running inside a web browser supporting Java. With this model, the user can access the same application without installing specific runtime software on the client. The use of an applet constrains the deployment, because standard restrictions for applets apply, such as restricted access to local resources and to servers.  
         [0080]     The process of presenting a form on the client device is now described within an embodiment of an architecture. The process will be illustrated for each of the main deployment profiles described above in  FIG. 4 . In the following figures, thick arrows represent the flow of information between stack layers. Notice that, in some embodiments, the grayed layers in the figures represent layers that are actually available on the computing system, although they are not used in the represented deployment profile. Alternatively, in some embodiments, the grayed layers may be absent.  
         [0081]      FIG. 5  illustrates the flow of information within the client and server stacks, for the thin connected profile.  
         [0082]      501  The process starts when the user raises an event on the device interface  10 , associated with an action provoking the presentation of a new form.  
         [0083]      502  The event manager  14  intercepts the event and sends the request to the requester  21 .  
         [0084]      503  The requester  21  transmits the request as an XML message to the listener  35  on the server  36 .  
         [0085]      504  The listener  35  analyzes the request and sends a command to the resource manager  34  to retrieve the XML file  520  containing the form specification. The resource manager  34  then parses the XML document into a DOM tree.  
         [0086]      505  The parsed DOM tree of the form specification  520  is passed to the processor  30 . The screen builder  32  uses this DOM tree to construct a new DOM tree representing the displayable interactive form. During this processes, the script engine  33  may be invoked in order to execute the construction of script code if any.  
         [0087]      506  As part of the construction process, the processor  30  may invoke the resource manager  34 , requesting some data from a database  521  to populate the displayable interactive form.  
         [0088]      507  The processor integrates the data in the form as specified in the form specification  520 .  
         [0089]      508  The listener  35  gets the DOM tree representing the visual form constructed by the processor  30 , generates the XML representation of the visual form and sends it back to the requester  21 . The requester then uses an XML parser to construct a DOM tree representing the displayable interactive form.  
         [0090]      509  Alternatively, the listener  35  may return a compiled version of the visual form to the compiled XML module  20  of the client device  22 , which in turn constructs a DOM tree representing the displayable interactive form.  
         [0091]      510  The DOM tree is passed to the UI Manager  11 , which generates the corresponding User Interface controls.  
         [0092]      511  The form is displayed on the device&#39;s interface.  
         [0093]      FIG. 6  illustrates the flow of information within the client and server stacks, for the thick connected profile.  
         [0094]      601  The process starts when the user raises an event on the device interface  10 , associated with an action provoking the presentation of a new form.  
         [0095]      602  The event manager  14  intercepts the event and sends the request to the requester  21 .  
         [0096]      603  The requester  21  transmits the request to the listener  35  on the server  36   
         [0097]      604  The listener  35  analyzes the request and sends a command to the resource manager  34  to retrieve the XML file  620  containing the form specification.  
         [0098]      605  The listener  35  gets the XML document representing the form specification  620  and sends it back to requester  21 . The requester then uses an XML parser to construct a DOM tree representing the form specification.  
         [0099]      606  Alternatively, the listener  35  may return a compiled version of the form specification to the compiled XML module  20  of the client device  22 , which in turn constructs a DOM tree representing the form specification.  
         [0100]      607  The parsed DOM tree of the form specification is passed to the processor  15 . The screen builder  17  uses this DOM tree to construct a new DOM tree representing the displayable interactive form. During this processes, the script engine  18  may be invoked in order to execute the construction script code if any.  
         [0101]      608  As part of the construction process, the processor  15  may invoke the resource manager  19 , requesting some data from a database  621  to populate the displayable interactive form.  
         [0102]      609  The processor then integrates the data in the form as specified in the form specification  620 .  
         [0103]      610  The DOM tree is passed to the UI Manager  11 , which generates the corresponding User Interface controls.  
         [0104]      611  The form is displayed on the device&#39;s interface.  
         [0105]      FIG. 7  illustrates the flow of information within the client stack, for the stand-alone profile.  
         [0106]      701  The process starts when the user raises an event on the device interface  10 , associated with an action starting the execution of script code.  
         [0107]      702  The event manager  14  intercepts the event, gets the script code associated with the event, and passes it to the processor  15 . The script engine  18  executes the script code.  
         [0108]      703  Within the execution of the script code, a new form is utilized. A command is sent to the local resource manager  19  requesting to retrieve the local XML file  720  containing the form specification, which is parsed into a DOM tree.  
         [0109]      704  The parsed DOM tree of the form specification is passed to the processor  15 . The screen builder  17  uses this DOM tree to construct a new DOM tree representing the displayable interactive form. During this processes, the script engine  18  may be invoked in order to execute the construction script code, if any.  
         [0110]      705  As part of the construction process, the processor  15  may invoke the resource manager  19 , requesting some data from a database  721  to populate the displayable interactive form.  
         [0111]      706  The processor integrates the data in the form as specified in the form specification  720 .  
         [0112]      707  The DOM tree is passed to the UI Manager, which generates the corresponding User Interface controls.  
         [0113]      708  The form is displayed on the device&#39;s interface.  
         [0114]      FIG. 8  illustrates the flow of information within the client and server stacks, for the applet profile. The client runtime runs within a Java compatible HTML browser  800  and the server  801  is a web server.  
         [0115]      802  The browser loads the applet client runtime code from the web server  801 . The client runtime then runs within the browser&#39;s JVM.  
         [0116]      803  The user raises an event on the HTML browser  800 , associated with an action starting the execution of script code.  
         [0117]      804  The event manager  14  intercepts the event, gets the script code associated with the event, and passes it to the processor  15 . The engine  18  executes the script code.  
         [0118]      805  Within the execution of the script code, a new form is required. A command is sent to the requester  21  requesting to retrieve a form from the server.  
         [0119]      806  The request is transmitted to the listener  35  within an HTTP request to the web server  801 .  
         [0120]      807  The listener  35  analyzes the request and sends a command to the resource manager  34  to retrieve the XML file  820  containing the form specification. The resource manager  34  then parses the XML document into a DOM tree.  
         [0121]      808  The parsed DOM tree of the form specification is passed to the processor  30 . The screen builder  32  uses this DOM tree to construct a new DOM tree representing the displayable interactive form. During this processes, the script engine  33  may be invoked in order to execute the construction script code if any.  
         [0122]      809  As part of the construction process, the processor  15  may invoke the resource manager  34 , requesting some data from a database  821  to populate the displayable interactive form.  
         [0123]      810  The processor then integrates the data in the form as specified in the form specification  820 .  
         [0124]      811  The listener  35  gets the DOM tree representing the visual form constructed by the processor  30 , generates the XML representation of the visual form and sends it back to the requester  21 . The requester then uses an XML parser to construct a DOM tree representing the displayable interactive form.  
         [0125]      812  The script that started the loading process of the form may perform some additional initializations, further manipulating the DOM tree.  
         [0126]      813  The DOM tree is passed to the UI Manager  11 , which generates the corresponding User Interface controls.  
         [0127]      814  The form is displayed on the device&#39;s interface.  
         [0128]     It should be noted that the applet profile is just one example of mixing the main profiles illustrated in  FIGS. 5, 6  and  7 . Capability is provided for mixing these profiles in many other ways. That is, a given application running on a given client device may combine the behavior of the three profiles. For example, an application on a PDA device may be developed to run in a thin client mode when connected to the corporate server within an intranet, thus taking advantage of real-time data, as illustrated in  FIG. 5 . Alternatively, when the same application recognizes the unavailability of a valid network connection, it may automatically revert to a stand-alone mode, using a local database that has been automatically synchronized during the connected mode. The same application may then run anywhere, such as at a customer&#39;s site.  
         [0129]     By reference to  FIG. 2 , an embodiment of the present invention comprises a visual design module  226 , used by the developer during the visual design step  202 .  FIG. 9  illustrates with more details of one example of a visual design module, in which the visual design module may comprise a project browser panel  901 , a properties browser panel  902 , and a preview and XML source panel  903 .  
         [0130]     The developer uses the building elements available from the visual design module to create the forms. For example, the following building elements may be provided: 
        Box  904 : A container for other objects.     Bulletinboard: A container for other objects, which may be placed at arbitrary locations.     Button  905 : An action initiator.     Checkbox: A Boolean indicator.     Grid: A container for tabular data. Sub-objects include columns and rows.     Image: A container for a picture.     Menulist: A drop-down selection list of menu items     Spring: A flexible spacing element to be used between other objects.     Text  906 : characters and labels.     Textfield  907 : An entry field.     For: A loop element to integrate data from a data source        
 
         [0142]     A building element may be given specific attributes, such as background color and font size through the properties browser  902 . Such built-in attributes are available for each building element and are presented within the built-in attributes tab  908 . Custom attributes may also be added to an element within the custom tab  909 .  
         [0143]     To define the behavior of the form, scripts may be added to the events presented within the event tab  910  of the properties browser. A building element has an associated list of built-in events that may be linked to script code. The script code may define the interaction code, the business logic and the computations required to process the event.  
         [0144]     External data may be used to customize the screen during the construction phase of a form; a for building element may be used for this purpose. Examples include populating a list of values in a menulist element or a grid element, with data extracted from a database table. Alternatively, the external data may be accessed by some script code executed during the processing of an event. One example includes checking a username and password against a credentials database table when a user validates a login form.  
         [0145]     When writing script code, the developer accesses the data sources and other resources like images as abstract resources, without specifying the physical location and connectivity properties of the resources. The mapping to actual resources is done in a later step. There is no means, during this phase, to state whether the resource will be located on the client device or on the server. This is a feature that allows a given application to be deployed on several different deployment targets.  
         [0146]     The visual design module translates the form specification  911  into an XML document that may be viewed and edited within the XML Source tab  912 . The hierarchical structure of XML is very well suited to represent visual components of a user interface. The developer may use the visual features of the visual design module; alternatively, the developer may directly edit the XML document representing the current form.  
         [0147]     By reference to  FIG. 2 , an embodiment comprises a deployment module  228 . When the form specifications have been created during the visual design step  202 , the developer proceeds to the define deployment step  206 , interacting with the deployment module  228 . The developer starts defining the platforms on which the application will run. Each platform may be characterized by: 
        The client device environment (e.g., the Java version, the device&#39;s profile).     A list of the form specifications deployed on the platform. Especially, some forms may not be deployed in all the platforms.     The involved servers.     The accessed databases and resources.        
 
         [0152]     Platforms can also be added or modified at any time. When a new platform is added, the designer tool  200  updates the relevant data.  
         [0153]     When the platforms have been defined, the developer requests the deployment module  228  to prepare the deployment of the platforms. The deployment module  228  analyzes the form specifications listed in the platforms, especially the scripts contained by the forms, and determines the involved abstract resources. A resource is either: 
        A form resource: a resource used during the construction process of the form. Since the construction process may be uniformly performed on the server or on the client device, the developer can consider performance issues when deciding where to locate the form resources.     Event resource: a resource used during the processing of an event of the form. Event processing is performed on the client device.        
 
         [0156]     For each abstract resource determined during the preparation process, the developer defines a mapping to an actual resource. Therefore, the developer sets the type of the resource, its location and its properties. For example, if the resource is a database table, the settings may include a reference to a database resource and the name of the table. Some resource definitions may be shared by different elements in one form or across different forms. External resources may be defined only once and used anywhere in the application.  
         [0157]     Once the deployment has been defined in the define deployment step  206 , the developer proceeds to the export deployment step  210 , using the deployment module  228  of the designer tool  200 . When the developer requests the deployment module  228  to export the deployment, the designer tool  200  creates all the files required by the deployment and copies the files and the resources either to the client or to the server according to the deployment definition. Alternatively, the developer may export the required files to an intermediary storage, such as a local disk, and later copy them to the final target. On the client  238 , the files to deploy include ready-to-deploy form specifications  216  and resources  218 . On the server  236 , the files to deploy include ready-to-deploy form specifications  220 , resources  222  and the server configuration file  224 . Several files and resources may be deployed, including images, queries or other resource files used by the application.  
         [0158]     By reference to  FIG. 2 , an embodiment comprises a test module  244 . After the deployment has been exported, the developer proceeds to test  240  the application. In accordance with one aspect, a process is provided to test applications on different platforms. Testing applications on small devices is a good way for the developer to get the real feeling of the user interface and to check the actual behavior of the application. The defined process promotes an iterative approach for testing. As discussed previously, the design step  202  can be performed only once for all the targeted platforms. To simplify the first testing iterations, the developer can define a test platform  242  on which to deploy the application, with the developer&#39;s desktop used as a client  238 . The deployment may include a server  236  accessible from the desktop in order to simulate the real-world environment. The developer then tests the application on this platform  242 . Once the functionalities are tested on the desktop test platform, the developer may proceed to test the application for each real targeted platform  242 . In one embodiment, the designer tool  200  interacts with device emulators to proceed to test the application against specific devices. If the actual client device is connected to the developer&#39;s desktop, the designer tool  200  may deploy the required files directly on the device when the deployment function is run.  
         [0159]     Embodiments of XML descriptors are now described by reference to  FIG. 10 . The XML syntax used in the different steps of the development process is described. The example illustrating the syntax is a simple window with a menulist containing a list of train stations extracted from a database.  
         [0160]     During the visual design phase  1041 , the developer visually defines the form  1011  and the designer tool generates the corresponding XML representation of the visual form specification  1001 . Conversely, the developer may edit the XML representation  1001 , and the designer tool will generate the corresponding form on the screen. In the example presented in  FIG. 10 , the visual components visible on the screen have corresponding elements in the shown descriptor example1.xml, for instance the menulist  1030 . The XML tag &lt;for&gt;  1023  is used to fill the menulist  1030  with items extracted from a database. The tag represents a loop on each item retrieved from the data source, and the value of the attribute datasource=“stations”  1021  names the source of the data to be used by this loop. This name is the name of the abstract resource representing the data source, and does not necessarily correspond to a physical database name. A mapping with an actual resource will be defined later. In the &lt;for&gt; declaration, the attribute cursor-name=“s”  1024  defines the cursor object used within the loop to access the items retrieved from the database. Within the loop definition, the access to the item&#39;s content is performed through the syntax s.field(‘STATION_NAME’)  1022 , giving access to the STATION_NAME field of the current item.  
         [0161]     To deploy the form, the developer first defines a deployment platform  1031 , named jdk1.3 in the example, and adds the form  1034  example1 to this platform. The developer: then launches the prepare deployment process on the designer tool. The designer analyzes the forms and finds in the form  1011 , as a consequence of the value of the attribute  1021 , an unknown abstract resource named stations  1035 . This resource is listed as a Form Resource because it is used within a &lt;for&gt; declaration. At runtime, &lt;for&gt; declarations are used during the construction of the form, and not during the processing of an event. The properties of the deployment represented on the properties browser  1012  correspond to a deployment definition contained in the XML project file  1002 . This file contains the list of the form specifications included in the project and the deployment definitions  1040  for the client and the server, and indicates all the resources used in the project.  
         [0162]     The developer defines a database by adding an element  1033  under the databases  1032  element in the project browser. The developer defines properties of the added database by providing suitable values for the database component properties on the properties browser  1012 , including the database&#39;s type and the settings for accessing the physical database. The corresponding syntax  1036  in the project file  1002  indicates that a database named localXML is located in a directory xmldb and corresponds to an XML file.  
         [0163]     In order to bind the stations data-source to the localML database, the developer sets the properties  1012  attached to the stations resource  1035  to the following values: 
        Type: Table. The resource is a database table        
 
         [0165]     Database Name: localXML. Corresponds to the logical name of the database containing the table  
         [0166]     Table Name: train.stations. Corresponds to the physical name of the table in the database.  
         [0167]     These settings are represented in the XML project file  1002  as: &lt;prebind name=“stations” databasename=“localXML” tablename=“train.stations” type=“table”/&gt;.  
         [0168]     The next step is the export deployment step. During this step, the designer tool generates the ready-to-deploy form specification  1003 . The designer tool combines the visual form specification  1001  with the contents of the project file  1002 , thus binding the abstract resources contained in the form specification with the physical resources as specified during the deployment definition  1040 . The binding syntax  1043  for the table is:  
         [0000]     &lt;prebind name=“stations” action=“table” protocol=“local” resource-name=“train.stations”db=“localXML”/&gt; 
         [0169]     The prebind tag is used to define a binding for a resource used during the construction of the form and corresponds to a form resource. Conversely, a bind tag is used to define a binding for a resource used during the processing of an event and corresponds to an event resource. The associated properties are: 
        Name: the logical name of the resource     Action: designs the type of action to be performed by the runtime when processing the bind or prebind elements. In the example, the table value indicates that data must be retrieved from a database table. The possible values for this attribute and the corresponding actions are: 
            query: retrieve data by querying a database     table: retrieve data from a database table     method: access a java method     file: retrieve a text file or an XML file     form: open a new form     openDatabase: connect to a database    
            resource-name: the name of the resource, database table in the example     db: the logical name of the database        
 
         [0180]     One major issue affecting the user experience with mobile devices is the latency when moving from form to form within an application. This is due to the connection and transfer time for the forms, and the poor performance of the devices&#39; processor. Embodiments provide additional capabilities, which may dramatically improve the perceptible performance of a mobile application. 
        Caching: If a form has been downloaded and processed by the device, the form remains in the device&#39;s memory as a processed form, and may be quickly and frequently accessed as required. The client runtime manages the list of loaded forms it can keep in memory, releasing cached forms as needed.     Pre-fetching: designated forms may be downloaded, processed by the device, and stored into the cache, during the idle time of the device&#39;s processor, even before the form has been explicitly requested by the user interaction within the application. Idle time typically occurs during user interaction. The client runtime may later access the form from the cache as required, without apparently incurring any download or processing time.