1. A DAPT IST-2001-37126 Task model as input for future deliverables Simon Woodman University of Newcastle

2. A DAPT Bologna Meeting February 2003 Aims and Objectives We need language to specify CSs Expressive to model arbitrarily complex services Deliverable D7 The task model is the first stage of developing the composition language

3. A DAPT Bologna Meeting February 2003 Tasks – Graphical Notation Single input set Multiple output sets –One output set for normal termination –Many output sets for abnormal terminations Each input and output set can contain one or more objects –object = wsdl:part Relationship to WSDL –Task ≈ wsdl:operation –Input/Output sets = wsdl:message and wsdl:fault IS OS1 OS2

4. A DAPT Bologna Meeting February 2003 Dependencies Data Dependencies –Tasks will only be started when all the data they require is available Temporal Dependencies –Tasks will only be started when another task has started/finished A A B B

5. A DAPT Bologna Meeting February 2003 Compound Tasks Tasks can be composed from compound tasks –Allows for recursive task composition A B E C D

6. A DAPT Bologna Meeting February 2003 Genesis Tasks The task definition is instantiated at run-time –Allows for just-in-time instantiation –Allows for recursive execution of defined workflows A A’ B

7. A DAPT Bologna Meeting February 2003 Flexible Task Model Event/Notification model The task model developed allows for: –Compensation tasks Forward Error Recovery Backward Error Recovery (compensating tasks) –Alternative tasks This can be used to provide Application Level Fault Tolerance

8. A DAPT Bologna Meeting February 2003 Notation So far we have mainly seen the graphical notation Newcastle is developing an XML based language which describes tasks in the task model shown

9. A DAPT Bologna Meeting February 2003 Relationship to other technologies BPEL – Consortium from IBM, Microsoft and BEA Systems –Developed from WSFL and XLANG WSCI – published by BEA Systems, Intalio, SAP, Sun Microsystems

10. A DAPT Bologna Meeting February 2003 Questions?