Thursday, August 02, 2007

The Information Model for Composite Services is not about Solving Service Versioning

The business process information model (BPIM) is not intended for solving versioning issues for a specific service, that can be solved using message duck-typing or consumer-driven contracts. The BPIM is for mediating semantics between independent and autonomous services, allowing the services to be composed into biz processes and still be able to evolve each service separately. The autonomous SOA tenet should be used to achieve shared services and interchangeagility rather than focusing solely on reusability. A service is not autonomous before you can use the scissors on parts of a business process and replace the service by e.g. outsourcing it.

Indeed, service versioning is important for the evolvability of the service itself, but the BPIM is about the agility of the business processes in your service-oriented solution.

Do not confuse the BPIM with the EAI CDM, they are similar concepts at different architectual layers. The BPIM will contain a subset of the common information model (CIM), but is rather focused on the data+business documents and semantics of the business events and processes that the information model encompasses. Design the BPIM based on the CIM, ensuring that the model is canonical for each business process domain. The BPIM is targeted at the service composition layer, not at the data access services layer.

Related reading: SOA doesn’t need a Common Information Model

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