| Abstract |
The growing market competition enforces companies to pursue increased efficiency and productivity, which is achieved by adopting workflow models for designing and executing their business processes. At the same time exploitation of the arising E-Service paradigm helps companies to focus on a principal business goal outsourcing secondary business goals to other organizations which constitute their business partners. This way operations of an enterprise or an organization become accessible via the web in the form of E-Services. E-Services can be distinguished into two broad categories, discrete (i.e add an object in a shopping cart, charge a credit card e.t.c) and session-oriented E-Services (i.e. teleconference, collaborative web browsing, interactive games e.t.c). Discrete E-Services have typically short duration and do not respond to asynchronous events. In the other hand session-oriented e-services have long duration and also the ability to both create (i.e. when a participant drops out of a teleconference) and respond (i.e. add a new participant to an already active teleconference session) to asynchronous events. Most of the E-Service composition languages support the definition of a top-level process which handles the interactions with the various E-Services as independent actions. Even though this model suffices in the case of discrete E-Services this is not the case for session-oriented E-Services. In the case of session-oriented E-Services the execution engine must be able to respond to asynchronous events and decide how they affect the active sessions (i.e. when a participant in an audio conference loses his connection the rest of the participants may have to be notified with a text message). This thesis studies and extends a process model and a composition and execution platform for both discrete and session-oriented E-Services. In contrast to other models the active flowchart model defines a process schema as a collection of active flowcharts, that is flowcharts coupled with the event class that enacts them, rather than defining a top-level process. A flowchart enactment can affect the state of a session modifying or event terminating it. The AZTEC platform for E-Service composition and execution is event-driven, supports explicit prioritization in the execution of active flowcharts and allows the concurrent execution of both multiple process instances as well as multiple flowcharts of the same process instance. Finally performance measures show that the system exhibits stable behaviour and low response times for both small and high event creation arrival rate.
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Γλώσσες και Πλατφόρμες Σύνθεσης Ηλεκτρονικών Υπηρεσιών
