Event vs Services to initiate a BPEL process in AS11

Since As11 supports both events and services to initiate a SOA composite ( may be having a BPEL process within it), there is always a question around when to use events and when to use service invocation to start the process.

The decision can be based on the following understanding of the events and service patterns.

Events

• Events are suitable for a decoupled integration.
  
• Events are one way messaging (no request response pattern and correlation)
  
• The publisher does not know about the subscribers (there might not be subscribers too)
• The publisher is not blocked for the execution of the subscriptions
• Events support 1:n fan out (multiple subscribers for the same event)
  

Service invocations

• Service invocation is a tight integrations with the service provider
• Service invocation supports request response patterns (sync or async)
• Synchronous service invocation is blocked till the execution of the service completes.
• Async Request response pattern is often supported via WS-adderessing and correlation

SpringOSGi M1 available for download...

This week SpringOSGI reached the first milestone. The availability to download it, added another OpenSource to OSGi(different than OGSI which is Open Grid Services Infrastructure) list of opensources.

http://sourceforge.net/project/showfiles.php?group_id=73357&package_id=227224

The list now goes on..Apache Felix, Equinox OSGi, KnopherFish OSGI, OXSA, Newton, and many others.

This year seems to be a good year to OSGI. Recently IBM and Cisco announced to develop Unified Communications and Collaboration(called UC2) platform based on OSGI. UC2 would not be an open source. So to increase the adoption by developers and industry, these companies would make UC2 freely available.

Anyway, coming back to OSGi which now has many mobile-telecom device vendors on its board. OSGIs start in 1999, it started with JSR-8 ( which was withdrawn). However, quite a few Mobile related JSRs like 232, 239, 246 (Mobile Specs) have come up based on works/concepts from OSGI ( and some JSRs like JSR 277 partially specified features thus became controversial) and some more are coming up JSR291 (Dynamic components) etc

Some of the concepts related to versioning, lifecycle managements, and various other services may find way beyond devices related to Web Services. Off-course, Webservices being stateless, there is already a debate whether 'lifecycle' management makes sense to Webservices or not. However, it all depends on what we makes sense as lifecycle management in the domain.