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Motivation | The Dialog Control Framework | The Dialog Flow Notation | Conclusion | References | Slides
A Dialog Control Framework for Hypertext-based Applications
The strict separation of user interface design, application logic implementation, dialog flow specification and dialog control logic in the Dialog Control Framework presented here has a number of advantages: Firstly, it enables a high degree of flexibility, reusability and maintainability for the components of all four layers. Secondly, presentation channel-independent applications can be built with minimal redundancy: Only the dialog masks and dialog flow specifications have to be adapted for different channels, while the application logic can be implemented only once and the dialog control logic is already provided by the framework. Finally, since the central dialog control logic is aware of the whole dialog flow specified for an application, it can provide mechanisms for the realization of complex dialog constructs. For example, the application developer can use context-independent dialog modules that may be nested, aborted and resumed without having to worry about event handling, stack management and resume point identification.
The associated Dialog Flow Notation is essential for providing the specification of the dialog flow to the framework. Since it does not require a detailed knowledge of the underlying protocols and technologies, but instead works with three relatively intuitively understandable concepts ("masks contain what the user sees, actions contain what the system does, and compounds contain transactions the user can perform"), it can also be used by people without programming experience, such as representatives of the application's target audience, usability experts and user interface designers. Therefore, the notation's dialog graph diagrams can be used as a communication tool throughout the software development process. In addition, the graphical dialog flow specifications can be transformed into XML documents by following a set of simple rules, allowing for a very efficient transition from specification to implementation.
This thesis provides the foundation for this approach to dialog control in hypertext-based applications by defining the basic concepts, elements and rules of the Dialog Flow Notation and providing a prototypical Dialog Control Framework implementation. Further research should examine how the robustness of the framework in unforeseen situations can be increased (e.g. when the user clicks the browser's Back button), how parameters can be associated with events to make them more flexible means for transporting information, and how the framework can be optimized to handle high load in a production environment.
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