Patent Publication Number: US-8990768-B2

Title: Software object property return method and system

Description:
BACKGROUND 
     The present invention relates generally to the field of interface devices and to their configuration and programming. More particularly, the present invention relates to techniques for manipulation of objects of industrial automation devices and their visual representations on the interface devices. 
     A wide range of interface devices are known and are presently in use in many different fields. In industrial automation, for example, human machine interfaces or “HMIs” are commonly employed for monitoring or controlling various processes. The HMIs may read from or write to specific registers such that they can reflect the operating state of various machines, sensors, processes, and so forth. The interfaces can also write to registers and memories such that they can, to some extent, control the functions of the process. In monitoring functions alone, little or no actual control is executed. In many other settings similar devices are employed, such as in automobiles, aircraft, commercial settings, and a host of other applications. In many applications, the interface may not communicate with a remote device or process, but may be operated in a stand-alone manner. 
     In these interface devices, various objects used in the interface may correlate to different controls, monitors, or any other parameter of an industrial automation device. Some of these objects may have visual representations on the interface devices, while other objects may not be visually represented but may be accessible for configuration and programming by a user. A user may desire to manipulate these objects, such as by creating new objects, deleting objects, or otherwise changing the state of an object to create and customize an interface. 
     In some instances, a user may access the interface devices via a client such as a web browser. In either case, the performance and responsiveness of the interface device or web browser may be affected by manipulation of the objects of the interface device. For example, the caching functionality of the web browser may result in caching a large amount of objects in memory, thus reducing the amount of memory available for execution of the interface. Additionally, transfer of data between the web browser, the interface device, and the industrial automation device may also affect the performance and responsiveness of the interface device and web browser. 
     BRIEF DESCRIPTION 
     The present invention provides a novel approach to interface device management and configuration designed to respond to such needs. The approach uses visual representations of a plurality of device elements operative on the interface device. A user may change the state of a device element, such as deleting the device element, and a user may also undo the operation such that the properties, connections, and text associated with a device element are restored. An entity may be created in response to the change in state of a device element and transferred to a browser running designer software or other application, so that the entity includes the properties, connections, and text of the original device element. 
     Methods, devices, and computer programs are all supported for performing these and other functions of the invention. 
    
    
     
       DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  is a general overview of a framework for an interface configuration system in accordance with certain aspects of the present invention; 
         FIG. 2  is a diagrammatical overview an interface for monitoring or controlling a process in accordance with an embodiment of the present invention; 
         FIG. 3  is an overview of certain of the functional components in an interface and a configuration station in accordance with an embodiment of the present invention; 
         FIG. 4  is an overview of certain views or containers of device elements in accordance with an embodiment of the present invention; 
         FIGS. 5A-5N  are an overview of a delete operation and undo operation on device elements of an interface in accordance with an embodiment of the present invention; and 
         FIG. 6  is a flowchart illustrating a process for a delete and undo operation on a device element of an interface in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     A number of facets, components and processes will be described through the following discussion. By way of introduction, a general system overview is in order that situates these innovations in context.  FIG. 1  is a diagrammatical representation of a control and monitoring software framework  10  for an interface in accordance with an embodiment of the present invention. The framework  10  facilitates building functional software by utilizing a module based interconnection mechanism  12 , which inherently supports dynamic manipulation and configuration. This dynamic manipulation and configuration ability facilitates efficient provision of feature-rich configuration environments for configurable interfaces. That is, as described below, individual device elements are provided as stand-alone code that can be individually programmed, pre-written for use, as in a library, customized in their function and appearance in screens, and interconnected to provide information to a user as well as monitoring and control functions. 
     The framework  10  includes two interrelated software environments that can reside on a single system (e.g., computer). Specifically, A run-time environment  14  enables an operator (e.g., a human user) to interact with an application, such as a process during run-time (e.g., during use of the interface, typically during interaction with or observance of a process in operation). A design-time environment permits a designer to configure the interface and its components. For example, a system may graphically present run-time information to an operator via the run-time environment  14  on a display (e.g., computer or interface device screen). Further, the system may include means (e.g., a keypad) for accepting operator input that can be detected and managed via the run-time environment. The environments interact as described in detail below, in innovative ways to provide greatly enhanced programming and use of the interface. 
     The run-time environment includes or provides access to device elements  18 . The device elements  18  are software components that may include any accessible or configurable element in a software environment. For example, the device elements  18  include software components, such as “ActiveX” controls or “.NET” components that are managed by the run-time environment  14 . “ActiveX” and “.NET” refer to object-oriented concepts, technologies and tools. Those skilled in the art will be well-acquainted with such programming approaches generally. In the present context, such standards should be taken as merely examples, and “device elements” should be understood as including any generally similar components or self-sufficient programs that can be run as quasi-independent elements, sometimes referred to as “objects”. Other standards and platforms exist for such elements, typically championed by different companies or industry groups. 
     Because such device elements are basic to certain of the inventive concepts, a few words of introduction are in order. Device elements generally include four features: properties, methods, connections (or connection points) and communications interfaces. Properties are attributes that can be adjusted, such as to define an image or representation of the element in a screen view, as well as its location on the screen, and so forth. A method is an executable function (sometimes referred to herein as the elements “functionality” or “state engine”), and defines an operation performed by execution of the element. A connection is a link between elements, and can be used to cause data (read from a memory or written to a memory) to be sent to another element. 
     Specific examples of device elements  18  may include software pushbuttons, timers, gauges, PLC communication servers, screens, and applications. In general, virtually any identifiable function may be configured as such an element. Moreover, as discussed below, such elements may communicate with one another to perform a wide range of display, monitoring operations and control functions. It should be noted that device elements  18  do not require special limitations for supporting a design mode. Also, while elements associated with an image are quite useful, particularly for screen views, many elements may not have a visual representation, but may perform functions within an HMI, such as calculations, or even management and data exchange between other elements. 
     The run-time environment typically operates using a communications subsystem  20 . The communications subsystem  20  is adapted to interconnect the device elements  18 . In practice, the communications subsystem  20  may be thought of as including the connections of the device elements. However, it may include a range of software, hardware and firmware that send data to and receive data from external circuits, such as PLC&#39;s, other computers, networks, satellites, sensors, actuators, and so forth. 
     The run-time environment typically operates using a behavioral subsystem  22 , which is adapted to manage the behavior of the device elements  18 . For example, responsibilities of the behavioral subsystem  22  may include the following: place and move device elements, modify device elements, group device elements on interchangeable screens, save and restore screen layouts, manage security, save and restore connection lists, and supply remote access to the run-time environment  14 . Here again, in practice, such behaviors may be defined as part of the profile (i.e., the “method” or “state engine”) of each device element. 
     The design-time environment  16  includes an advanced implementation of the behavioral subsystem  22  that facilitates direct or indirect manipulation of the run-time environment  14 , without impeding or compromising the behavior of the run-time environment  16 . That is, design and reconfiguration can be done even while an interface is operating. The behavioral subsystem  22  extends access to the run-time environment  14  via remote provision of the design-time environment  16 , such as in a conventional browser. The behavioral subsystem  22  allows a designer to interact with and change aspects of the run-time environment  14  of an HMI via a remote configuration station by serving the design-time environment or aspects thereof to the configuration station from the HMI. For example, an HMI coupled to a laptop via a network may provide a user with configuration capabilities by serving up a specific design-time environment to the laptop via the network. 
     Details and examples of how this may be done are provided below. In current embodiments, the design-time environment may be a product of combining Dynamic Hypertext Markup Language (DHTML) and an Active Server Page (ASP) server scripting to serve dynamic content to a browser. An ASP script is specially written code that includes one or more scripts (i.e., small embedded programs) that are processed on a server (e.g., Web server) before the page is sent to a user. Typically, in conventional usage, such script prompts a server to access data from a database and to make a change in the database. Next, the script typically builds or customizes the page before sending it to the requestor. As discussed below, such scripting is used in the present framework quite differently, such as to build screen views without prior knowledge of either the functionality of device elements, or their interrelationships. 
     By facilitating changes to device elements, the design-time environment allows the designer to make interchangeable design-time models or specialized implementations of the behavioral subsystem  22 . A specific example of a design-time implementation of the behavioral subsystem  22  includes a Web-based design-time environment, which extends access to a run-time environment on an HMI via a TCP/IP connection between the HMI and a remote device. The Web-based design-time environment facilitates management of the device elements without compromising run-time performance or security. In one specialized implementation the behavioral subsystem  22  gives designers the ability to manipulate aspects of the run-time environment  14  using a Web browser that is capable of accessing a related interface or HMI. As noted above, and as described in detail below this is achieved by using a combination of dynamic content, scripting, and configuration of the device element properties. 
       FIG. 2  is a diagrammatical representation of a control and monitoring system  24 , such as for industrial automation, implementing the framework described above in accordance with an embodiment of the present invention. The system includes an HMI adapted to interface with networked components and configuration equipment. The system  24  is illustrated as including an HMI  26  adapted to collaborate with components of a process  28  through a control/monitoring device  30  (e.g., a remote computer, programmable logic controller (PLC) or other controller). The HMI  26  may physically resemble existing hardware, such as a panel, monitor or stand-alone device. 
     Collaboration between the HMI  26  and components of the process  28  may be facilitated by the use of any suitable network strategies. Indeed, an industry standard network may be employed, such as DeviceNet, to enable data transfer. Such networks permit the exchange of data in accordance with a predefined protocol, and may provide power for operation of networked elements. As noted above, while reference is made in the present discussion to networked systems and to systems incorporating controllers and other equipment, the HMI  26  and programming techniques described may be equally well applied to non-networked components (e.g., GPS displays, game displays, cell phone displays) and to networked systems outside the industrial automation field. For example, the arrangements and processes described below may be used in facilities management, automotive and vehicular interfaces, computer numeric control (CNC) machines, point of sale (POS) systems, control interfaces for commercial markets (e.g., elevators, entry systems), and so forth, to mention only a few. 
     The run-time or operation environment constructed and managed by a corresponding behavioral subsystem, is stored on and resident in the HMI  26 . For example, such a behavioral subsystem can be adapted to load the application configuration framework (e.g.,  10 ) from a storage location, such as during initial manufacture or setup of the HMI. When loaded, the stored application framework may be adapted to create screens and locate user interface device elements (actually images or pictorial representations corresponding to the elements) in the screens. These applications, screens, and user interface elements are each types of device elements. As described below, the HMI  26  includes a stored application that dictates the layout and interaction of the device elements. The Web-based design-time environment, which is based on a run-time engine, is also loaded and resident on the HMI. The design-time environment may be adapted to handle advanced features (e.g., security management) for both design-time and run-time environments. 
     The HMI may be adapted to allow a user to interact with virtually any process. For example, the process may comprise a compressor station, an oil refinery, a batch operation for making food items, a mechanized assembly line, and so forth. Accordingly, the process  28  may comprise a variety of operational components, such as electric motors, valves, actuators, sensors, or a myriad of manufacturing, processing, material handling and other applications. Further, the process  28  may comprise control and monitoring equipment for regulating process variables through automation and/or observation. The illustrated process  28  comprises sensors  34  and actuators  36 . The sensors  34  may comprise any number of devices adapted to provide information regarding process conditions. The actuators  36  may similarly include any number of devices adapted to perform a mechanical action in response to an input signal. 
     As illustrated, these sensors  34  and actuators  36  are in communication with the control/monitoring device  30  (e.g., a PLC) and may be assigned a particular address in the control/monitoring device  30  that is accessible by the HMI  26 . The sensors  34  and actuators  36  may be in direct communication with the HMI  26 . These devices may be utilized to operate process equipment. Indeed, they may be utilized within process loops that are monitored and controlled by the control/monitoring device  30  and/or the HMI  26 . Such a process loop may be activated based on process inputs (e.g., input from a sensor  34 ) or direct operator input received through the HMI  26 . 
     The server software on the interface permits viewing of the development environment, and direct reconfiguration of the interface (particularly of the device elements and their associated appearance and functionality) without the need for special viewing or configuration software. This benefit flows from the fact that the device elements and the design-time environment itself is resident in the HMI, and “served up” by the HMI to a browser or other general purpose viewer on the configuration station. In other words, necessary support for external computer workstations (e.g., laptop and desktop computers) may be reduced or eliminated. It should be noted that reference to a “browser” for viewing and modifying configuration of the interfaces is not limited to Web browsers or to any particular browser. References to a browser are intended to be exemplary. More generally, the term “browser” is utilized herein to reference software which includes any general purpose viewer. 
     The HMI  26 , through the programming of the device elements as described below, may be thought of as including instructions for presenting one or more screen views, and device elements executed upon interaction with the HMI by reference to the screen views (e.g., pressing a button, touching a location of a screen, and the like). The screen views and device elements may be defined by any desired software or software package. For example, the screen views and device elements may be called by or executed by an operating system  38 . The device elements, as discussed above, in accordance with present embodiments, are objects conforming to “.NET” or “ActiveX” standards. The operating system itself may be based upon any suitable platform, such as Window CE. As referenced herein, the device elements and tools support Web services or technology for transmitting data over networks (e.g., the Internet). These device elements thus follow a set of rules regarding information sharing and are adapted for use with various scripting and programming languages, as described below. Such device elements enable provision of interactive content to outside applications such as a LAN, WAN, an intranet, an extranet, or even the World Wide Web. Accordingly, the operating system  38  and the various device elements facilitate dynamic configuration of the HMI  26  through a browser by allowing configuration access (e.g., serving up) to the browser. 
     For example, such configuration access includes access for instantiation of device elements. In other words, new device elements can actually be created and implemented from the browser. Again, it should be noted that the browser does not require actual functional access. Indeed, in one embodiment, requests via the browser result in a “draw” sequence of operations based on data functionality and content of device elements in a container, thus allowing illustration of the device element representations and access to their configuration without actually serving up functional aspects. This allows for configuration via a remote workstation without necessitating technical support for the remote workstation. Such aspects are described in greater detail below. 
     In addition to the operating system and device elements as described above (and as described in greater detail below), the HMI  26  includes an application or application layer  40 . The application, which may itself comprise a device element, facilitates access to and acquisition of information from the various device elements of the HMI. In particular, the application  40  represents a first level in a multi-level device element that can be enumerated for execution. The application  40  in a practical implementation may comprise a user application in the form of an XML page. The user application is then interacted with by the user or operator, as well as by the designer as described in greater detail below. 
     The screen views and device elements may be described as independent executable pieces of software. In a present implementation, the screen views are defined by appropriate code written in a markup language (e.g., Hypertext Markup Language or HTML). Thus, the configuration of graphical interface screens for the HMI  26  may be performed without the use of conversion programs. Further, by programming of the device elements, the screen views may be developed directly on the HMI  26  via resident server software (designated as server  42 ) that makes the resident development environment available for remote access. Specifically, in one embodiment, representations of certain device elements (e.g., ActiveX controls) are served up to the browser without serving up the software components themselves. Because a development or design-time environment may be accessed via a browser, the need to download changes to the screens and to update remote configuration software applications can be eliminated. 
     As noted above, device elements may include functionality by which they read from or write to specific memory or registers of memory, typically in other devices (but which could also be within the HMI). For example, a particular function may correspond to writing to or reading from a register  32  of control/monitoring device  30 . In a simple case, for example, an object simply accesses a piece of data (e.g., a state of a component as determined by a sensor), and generates an output signal to write a value corresponding to the state of a different networked device. Much more complex functionality can, of course, be configured. In an industrial control and monitoring context, for example, such device elements may emulate operation of a range of physical components, such as a momentary contact push button, a push button with delayed output, a switch, and so forth. Many pre-programmed device elements may be available for use by the HMI  26 . Such functional modules may be accessible via a network, or may be resident on the HMI  26 , or resident on a separate device directly linked to the HMI  26 . In this way, an HMI supplier or software supplier may provide many possible building blocks from which screens and complex control and monitoring functions may be programmed. Indeed, a library  44  of available device elements may reside on the HMI  26  to facilitate configuration of the HMI  26 , as described below. The screen instructions may call upon the device elements for performing desired functions based upon operator inputs, and these instructions may be programmed into versions of the pre-programmed elements. For example, the operator may provide initiating inputs by touching a location on a touch screen or depressing keys on a keyboard. Based upon the screen instructions and the device elements associated with the instructions (e.g., with specific locations triggering calls or execution of pre-configured device elements) the desired functions may then be executed. Accordingly, the operator is enabled to interact with a process, typically to change screen views, write to registers, or command the generation of other output or control signals. In a stand-alone implementation, the interactions may simply recall or store data, change screens, and so forth. 
     One or more separate interface screens may be employed, with some HMIs having many such screens and a great number of device elements. Each device element may, in turn, be uniquely programmed to consider specific inputs, perform specific functions, and generate signals for specific outputs. A plurality of such device elements can be loaded and hosted in a single software “container” (e.g., ActiveX container) as described below. 
     The HMI may be configured by interacting directly with a panel or screen on the HMI itself (if one is present), but in many cases configuration will be performed from a remote configuration station  46 . For example, access is provided directly to the resident library  44  and/or operating system  38  and application  40  via a browser  48  or similar application. In a present implementation, no other specialized software is required at the configuration station  46 . Indeed, the server  42  resident on the HMI  26  may provide access to the device elements in library  44 . By storing the device elements in library  44  directly on the HMI  26 , the risk of version conflicts and so forth are eliminated or reduced. Additionally, the HMI may be directly connected to the configuration station, or accessed by reference to an IP address (Internet Protocol address) assigned to the HMI  26 . 
     Access control schemes may be used to limit the ability to change screens and device elements. For example, a password or user access status may be required to gain such access. Further, in a presently contemplated embodiment, the configuration station automatically recognizes the HMI or the terminal on which the HMI is resident as a device upon being coupled to the configuration station (e.g., similar to an external memory or drive). Thus, once connected to the configuration station, the HMI may simply be “recognized” as a device that can be accessed (providing the configuration screen and tools described below). 
     Once the device elements then resident on the HMI  26  are accessible to the configuration station  46 , aspects of the HMI  26  can be modified or updated directly on the HMI  26  via the communication link from the configuration station  46 . For example, a user may wish to update a particular HMI graphic to provide data, such as historical data or trending relating to information being received from a newly installed sensor  34 . Additionally, the user may find it desirable or convenient to update the HMI graphic for presentation of such data while in an off-line mode (e.g., without immediately implementing the changes). In such a scenario, the user may link to the library  44  of available device elements via the configuration station  46  and use them to modify the HMI graphic or functionality in a development environment. 
     It should be noted that additional device elements can be added to the library  44 . For example, if a trending device element is not resident on the HMI  26 , a user can download such an element to the HMI  26  from a configuration library  50  resident on the configuration station  46 . Alternatively, a user could access the trending device element from a resource library  52  accessible via a network (e.g., the Internet), either directly to HMI  26  or through the configuration station  46 . This may be particularly beneficial because new and improved device elements can be downloaded to the HMI  26  individually and on a periodic basis, thus adding new functionality without necessitating the periodic release of new conversion programs or HMI operating systems, or run-time or design-time environment software. The development environment may provide links to such libraries. Further, in embodiments using embedded code (e.g., operating system, server software, device objects, etc.), because the embedded code resides on the HMI  26 , version conflicts with the embedded code may be avoided and the necessity for configuration station software upgrades may be eliminated. 
       FIG. 3  is a high-level flow diagram representing interaction between an HMI and a configuration station. More detail regarding such processes is provided below. In general, a platform for the HMI and configuration station will include the operating system or executive software  38 , application software  40 , as well as any communication software, a microprocessor, a network interface, input/output hardware, generic software libraries, database management, user interface software, and the like (not specifically represented in  FIG. 3 ). In the illustrated embodiment, a design-time platform and a run-time platform interact within the HMI. The design-time platform provides views that are served as the design-time environment  16  to a desktop personal computer platform (e.g., running a suitable operating system, such as Windows XP, Windows Vista, or Linux) and the run-time platform cooperates with the design-time platform via the operating system (e.g., Windows CE, Linux). The design-time platform provides dynamic server content  54 , while the run-time platform displays views on the HMI itself (if a display screen is provided on the HMI). The design-time environment  16  is displayed in a browser  48  (e.g., Web browser or other general purpose viewer). 
       FIG. 3  represents at a very high level how the design-time environment  16  interacts with the operating system  38 , application  40  and run-time environment  14 . The arrow  56  represents dynamic exchange of content between the HMI  26  and configuration station  46 . In general, interaction with the design-time environment is the task of a designer  58  who initially configures the HMI screens or views, device elements, their functions and interactions, or who reconfigures such software. The run-time environment is generally interacted with by an operator  60  directly at the HMI. It should be noted that while the design-time environment  16  has specific needs, in a current embodiment, it depends heavily on the operating system, application and run-time environment. The design-time environment  16  and the run-time environment  14  may utilize certain base technologies (e.g., DHTML, HTML, HTTP, dynamic server content, JavaScript, Web browser) to operate respectively in the design-time platform and run-time platform. While, in the illustrated embodiment, the run-time environment  14  and the design-time environment  26  reside on separate platforms, in some embodiments they may reside on the same platform. For example, the design-time platform and run-time platform may be configured as or considered a single platform. 
     In one embodiment of the present invention, a design-time Web implementation is utilized. This design-time Web implementation offers the speed and flexibility of software running on the design-time platform by using a Web browser (e.g.,  48 ) with DHTML support from the HMI, as noted by the dynamic server content  54  in  FIG. 3  and as described below. DHTML is used to perform dynamic manipulation of Web content in the design-time environment  16 . Further, the dynamic server content  54  is used in the HMI to serve dynamic Web content to the design-time environment  16 . This dynamic client-server environment allows the Web browser to simulate an application running on the design-time platform without requiring a piece of software compiled for a related processor. 
       FIG. 4  is a diagram illustrating one or more device elements in a design-time environment in accordance with embodiments of the present techniques. The diagram includes interactions illustrated by relationships between a display  100  (e.g., a screen for browser display), a property editor  102 , and an HMI  26 . 
     The design-time environment represented by the configuration screen or display  100  includes static content  104  and dynamic content. The dynamic content includes images corresponding to any displayed or represented device elements  106  (e.g., virtual on/off button, gauge). In one embodiment of the present techniques, the image is specified by an image tag in HTML and is part of a JPEG file created by the HMI as described below. The static content  104  may be created by the ASP server or it may preexist in an HTML file. It should be noted that, in some embodiments, designated designers only can edit the static content  104 . 
     In the representation of  FIG. 4 , the device element representation  106  is contained within a view container  108 . As will be appreciated by those skilled in the art, a container generally defines a portion of a processing space in which certain device elements are opened and ready for use. The container  108  may thus correspond to a first view container that includes only the elements viewable within the current screen. As discussed above, many such screens may be provided in the HMI. Other screens, such as alternative control or interface screens may be provided in other view containers, such as a container  110 . In general, to speed the operation (e.g., changing between screen views) of the HMI, such view containers are predefined and associated with one another by definition of the individual device elements with which they are either associated or within which representations of the device elements are provided. A global container  112  is defined that include all of the device elements necessary for the various view containers, as well as other elements that may not be represented in any view container. As illustrated in  FIG. 4 , therefore, view container  108  includes the virtual button  106  which performs a “jog” function and is manifested by a representation in a first screen. New container  110  includes several components, such as a “start” button  114 , a “stop” button  116 , a virtual gage  118  and a digital readout  120 . The global container  112 , then, will include all of these device elements for the various view containers, as well as any device elements  122  that are required for operation of the viewable device elements but that are not themselves viewable. Such device elements may include elements that perform computations, trending, communications, and a wide range of other functions. 
     All device elements that are needed for the various views are opened during operation of the HMI and remain open in a single global container  112 . However, utilizing aspects of current technologies, known as “tear-offs” any device elements that are not required for viewing or operation of a current view (i.e., a view currently displayed on the HMI or configuration station view) are reduced in size to reduce the memory requirements, processing requirements, and to facilitate operation of the HMI. The “torn-off” device elements nevertheless remain open and active such that change in between screen views is extremely rapid and efficient from memory utilization and processing standpoints. 
       FIG. 4  also illustrates a property editor  102  in which a user may access various properties of the element  106 . As discussed above, the element  106  may also include connections and text associated with the element  106 , which may also be configured by the user via an editor, similar to the property editor  102 . 
     In an embodiment, the property editor  102  may interact with the HMI  26  a query string from the browser  48  to a server  96  (e.g., HTTP server) that is resident on the HMI  26 . The server  96  cooperates with an ASP server  98  including a dynamic-link library (DLL)  122  to receive and respond to queries. The DLL  184  allows for storage of executable routines as separate files, which can be loaded when needed or referenced by a program. In the example set forth above, upon receiving the call, the page is reloaded by the ASP server  98  and the query string is initially parsed resulting in evaluation of the move command. Server side scripts then access the device element  18  related to the image  106  and to update its location property. The new property information is then updated on the page and the page is passed to the browser  48 . 
       FIGS. 5A-5M  depict a change in the state of a device element, e.g., the deletion of a device element, and the corresponding undo operations in accordance with an embodiment of the present invention. As explained further below, to improve performance and responsiveness of the browser  48 , in order to save data for later undo operations, modifications to the state of a device element on the browser  48  result in a capture of the state of an device element and a transfer of the state information to the HMI  26 . Additional changes in the state of a device element will result in additional states being captured and sent to and stored on the HMI  26 . In this manner, a user of the browser  48  may manipulate the state of a device element and rely on previously stored states for undo operations without suffering a decrease in performance of the browser  48 , HMI  26 , or interface and application running in the browser  48 . 
     Beginning with  FIG. 5A , a web browser  48  includes a display  100  having static content  104  and dynamic content, as described above. A user may view and manipulate device element representations  106  and  200  contained within a view container  108 . The device element representation  106  corresponds to the device element  18  on the HMI  26 . Additionally, the device element representation  200  corresponds to a device element  202  on the HMI  26 . 
     As mentioned above, the device element representations  106  and  200  may be any type of device element, e.g., object, such as a control, a gauge, an indicator, etc. Additionally, various non-viewable device elements may be included in a global container that may be required for the interface the user is managing or configuring. In an embodiment, a user may desire to configure an interface by adding or removing device elements in the view container  108 , or, alternatively, in a global container. 
     In  FIG. 5A , to manipulate a device element, a user may first select the device element representation  106  as indicated by dashed area  204 . A user may choose to change the state of the device element  18  by the interface loaded in the browser  48 , such as by deleting device element representation  106 . Various other changes to the state of a device element  18  may be performed by a user, such as various levels of deletes, changing the properties of a device element  18 , changing the connections of a device element  18 , etc. The delete or other state change command may be sent to the HMI  26 , as indicated by arrow  206 . 
     As illustrated, the device element  18  may include various data, such as properties  208 , connections  210  (e.g., connections to other device elements), and text  212 . The visual representation of the device element  106  on the browser  48  is representative of the device element  106  and all of the additional properties  208 , connections  210 , and text  212 , which are stored on the industrial automation device  30 . Similarly, the device element  202  may include data such as properties  214 ,  216 , and  218 . As only visual representations  106  and  200  of the device elements  18  and  202  is displayed in the browser  48 , the data associated with the device elements  18  and  202  is not stored on the browser  48 , thus freeing up memory or other resources of the browser  48 . 
     As mentioned above, a user can manipulate device element representation  106 , such as by deleting the representation  106 . In an embodiment, deleting the representation  106  may delete the device element  18  from the HMI  26 . Alternatively, in other embodiments a delete command or a variation thereof may delete the device element representation  106  from the view container  108  but retain the device element on the HMI  26 . 
     In the event that a user deletes the device element representation  106 , a user may subsequently desire to undo the delete command or other change in state of the device element  18 . To facilitate storing of the data necessary for the undo operation, i.e., the state of a device element at the moment a user changes the state, the various properties, connections, and text of the device element may be bundled together and stored as an entity. For example, as illustrated in  FIG. 5B  and arrow  219 , as a user executes a delete operation on the device element representation  106 , the HMI  26  “bundles” all of the data of the device element  18  being copied into a separate entity  220 . In an embodiment, the entity  220  may be referred to as a “Blob.” The entity  220  may include data to capture the state of the device element  18 , such properties  222 , connections  224 , and text  226  that correspond to the properties  208 , connections  210 , and text  212  of the device element  18  being deleted. Although the data of a device element may be stored in the entity  220 , the entity  220  is not usable as the device element itself, but instead is used for storing, serializing, and transferring a device element and all of its associated properties, connections, and text. Additionally, as mentioned above, creating the entity  220  on the HMI  26  where the device element  18  is stored ensures that the undo operation will include all of the data associated with the device element  18 . 
     As illustrated in  FIG. 5C , after the entity  220 , the entity  220  may be serialized and transferred to the web browser  48 , as indicated by arrow  228 , such as via HTTP or any suitable protocol. In one embodiment, the entity  220  may formatted in Extensible Markup Language (XML) format. In other embodiments, the entity  220  may be described in any suitable format. Further, in some embodiments, the entity  220  may be compressed before serialization and transfer, to minimize the size of the entity  220  and increase the speed of the transfer. Additionally, in alternate embodiments, the entity  220  may be stored in a non-volatile memory of the HMI  26 , such as saved to a hard disk drive, flash memory, etc. 
     As illustrated in  FIG. 5D , the entity  220  may now be stored in the application running the web browser  48  after completion of the delete operation. The delete operation is completed on both the browser  48  and the HMI  26 . For example, the device element  18  may be removed from the HMI  26 , such that only device element  202  is left on the HMI  26 . Similarly, the device element representation  106  is deleted from the browser  48 , leaving only device element representation  200 . 
     To insure future undo operations, the web browser  48  and any application executing therein only stores the entity  220 . Because the entity  220  is smaller than the device element  106 , such as through data aggregation and compression as discussed above, the entity  220  uses significantly less resources of the web browser  48  and associated computer. Additionally, the web browser is only storing entities for undo operations, such as for the state of those device elements that have been changed, so not all device elements or entities thereof need to be stored. 
       FIGS. 5E  though  5 H illustrate deletion of another device element  202  and stacking of “blobs” for subsequent undo operations. As shown in  FIG. 5E , a user may select another device element representation  200 , as shown by dashed area  230 , to change the state of device element  202 , such as by deleting. As previously stated, because of the previous delete operation on device element  18 , an entity  220  is stored on the browser  48  that includes the state of device element  18  at the moment of deletion. 
     Similar to the deletion of device element  18 , once a user selects device element representation  200  and initiates a delete operation, the delete operation is communicated to the HMI  26  (arrow  232 ) and an entity  234 , or “blob,” is created on the HMI  26  to capture the state of device element  202 , as in  FIG. 5F . The entity  234  may include the properties  214 , connections  216 , and text  218  of device element  202 . As stated above, the entity  234  is used for storing, serializing, and transferring the data that includes the state of device element  202  at the time of deletion. 
     As illustrated in  FIG. 5G , the second entity  234  may be transferred to the browser  48  (arrow  236 ) to store for any subsequent undo operations. Both the previously created entity  220  and the second entity  234  are stored in the browser  48 . The entities  220  and  234  and any subsequently created entities may be stored according to a last-in-first-out (LIFO) principle, so that the next undo operation will case the last received entity to be transferred back to the HMI  26 . In  FIG. 5H , after completion of the delete operation, the device representation  200  is deleted from the browser  48  and, correspondingly, the device element  202  is deleted from the HMI  26 . 
       FIGS. 5I-5N  illustrate an undo operation that restores a device element from a stored entity in accordance with an embodiment of the present invention. As shown in  FIG. 5I , a user may desire to undo the deletion of device element  202  by selecting the appropriate undo command from the interface of the application in the browser  48 . As illustrated by the dashed area  236 , after a user initiates the undo operation the device element representation  200  may appear in the browser  48 , and the undo operation is communicated to the HMI  26  (arrow  238 ). As stated above, the undo operation may cause the last received entity to be transferred to the HMI  26 . For example, as shown in  FIG. 5J , for the undo operation of the deletion of the device element  202 , the entity  234  may be transferred back to the HMI  26  as illustrated by arrow  238 . The previously received entity  220  remains stored on the browser  48 . 
     As shown in  FIG. 5K , once the HMI  26  receives the entity  234 , the HMI  26  deserializes and unpacks the entity  234 , restoring the device element  202  on the HMI  26 . Additionally, in some embodiments the entity  234  may be compressed before sending to the HMI  26 , thus the HMI  26  may also decompress the entity  234 . Because the entity  234  stored the connections  214 , properties  216 , and text  218  of the device element  202  at the time of the change in state of the device element  202 , e.g., the delete operation, the restoring the device element  202  from the entity  234  restores the device element  202  to its state just prior to the delete operation. In this manner any change in state may be preserved for subsequent undo operations. 
     A user may also desire to undo the change in state, e.g., deletion, of other device elements, such as device element  18 . As shown in  FIG. 5L , a user may initiate an undo operation of the deletion of device element  18 , as shown by the appearance of device element representation  106  and dashed area  240 . Again, the undo operation may be communicated to the HMI  26 , as shown by arrow  242 . During the undo operation, the entity  220  is transferred to the HMI  26 , as illustrated in  FIG. 5M  by arrow  242 . Again, in one embodiment the entities may be stored and accessed according to a last-in-first out, so that an undo of the previous operation causes the next-oldest entity to be transferred t the HMI  26 . As stated above, once the HMI  26  receives the entity  220 , it deserializes and unpacks the entity  220 , and may also decompress the entity  200  if the entity has been compressed before transfer. Because the entity  200  was created just prior to the change in state, e.g., deletion, of the device element  18 , upon restoration of the device element  18  from the entity  234 , all the properties  208 , connections  210  and text  212  associated with device element  18  are restored, as shown in  FIG. 5N . Thus, as a result of two consecutive undo operations, the device elements  18  and  202  are restored to the HMI  26 , as depicted by the device element representations  106  and  200 . 
       FIG. 6  illustrates a process  300  illustrating the undo operation execution as described in  FIGS. 5A-5L  in accordance with an embodiment of the present invention. Initially, a user may select a visual representation of a device element in a screen of a web browser (block  302 ) running in an application, e.g. a design application for configuring an industrial automation device. A user may then select a delete operation on the selected device element (block  304 ). The initiation of the delete operation is communicated to the HMI (block  306 ), which then creates an entity that includes all of the properties, connections, and text included with the design element (block  308 ). 
     Once the entity for a design element is created, the entity may be compressed to reduce the size of the entity (block  310 ). After compression, the entity is serialized and transferred to the web browser and design application (block  312 ), via HTTP or any other suitable protocol. The HMI  26  may delete the device element from the HMI, and the corresponding device element representation may be removed from the browser  48  (block  314 ). A user may then select an undo operation on the selected device element (block  316 ). The initiation of the delete operation initiates transfer of the entity to the HMI (block  318 ). The industrial automation device deserializes and unpacks the entity, creating a copy of the original device element (block  320 ). Thus, at the end of the operation, the device element (block  322 ) is restored on the HMI in the same state as before the deletion. 
     While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.