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Termination Condition for Event Handlers in Workflow Management Systems

IP.com Disclosure Number: IPCOM000020712D
Original Publication Date: 2003-Dec-10
Included in the Prior Art Database: 2003-Dec-10
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Abstract

Event handlers, as specified for example in the Business Process Execution Language for Web Services standard proposal (see the appropriate OASIS TC homepage), provide for the processing of sets of activities parallel to the main part of a business process managed by a workflow management system..Event handlers are associated with scopes or the whole process. They are activated when the process navigates into the scope with which the event handler is associated and are de-activated when the process is ready to navigate out of the scope. An activated event handler is started when an appropriate message is sent to the process or a timer goes. The event handler finishes upon completion of the enclosed activities. Navigation of the process does not continue until all event handlers have completed. A process waits indefinitely if the event handler does not finish. Adding a termination condition to the event handler provides for specification of conditions under which an event handler should terminate.

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Termination Condition for Event Handlers in Workflow Management Systems

Workflow management system support the definition and execution of business processes. A detailed description of such a system and its capabilities can be found in the book authored by F. Leymann and Dieter Roller, Production Workflow: Concepts and Techniques, Prentice Hall, 2000. Description of business processes is done either by some graphical end user interface or more importantly by some language. The purpose of the language is to define precisely all functions that can be used when describing business processes. One of these functions that can be defined for a business process are event handlers. Event handlers are either associated with a set of activities, usually called a scope or a sphere or with the whole process. An event handler is activated when navigation through the process enters the scope or in the case of an event handler attached to the process, when the process is started. An event handler is deactivated when navigation is ready to leave the scope or in the case of an event handler associated with the process, when the process finishes. When the scope or processes, event handlers are allowed to complete; event handlers are considered to be short-running only. Event handlers are instantiated as the result of an external message or the triggering of a timer. The body of an event handler consists of a set of activities that are carried out when the event handler is instantiated. As an event handler is expected to finish very quickly, certain activities are basically excluded for usage in an event handler. Typical examples are the repetitive execution of a set of activities or the waiting for a timed trigger to go off. This undesirable limitation can be overcome by introducing the notion of termination conditions for event handlers.

    The Business Process Execution Language for Web Services (BPELWS), jointly authored by BEA, Microsoft*, IBM**, and Siebel and submitted by the companies to OASIS for standardization, is such a language for defining business processes. Explanation in this disclosure are made in terms of BPEL4WS constructs. However this is for illustration purpose only; any other method for describing business processes including other languages can be substituted for explaining the concept of termination conditions for event handlers.

    Event handlers are specified in BPEL4WS via the eventHandlers element as follows :

<scope>

<eventHandlers>

<onMessage>

<onAlarm>

</eventHandlers>

</scope>

    Event handlers that are activated via an external message are defined via the onMessage element; event handlers that are activated via a timer are defined via the onAlarm ele...