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Subject: Re: [ebsoa] Does SOA Require Registry-Based Dynamic Discovery?
Joseph: No it does not IMO. The SOA Manifesto When we elected to pursue the SOA reference model, we started analyzing architectures that claim to be SOA and looked at the abstract elements that are present in 100% of all SOA's. There is a concept of service advertisement - a concept of advertising the service description (including contract) to the community of potential service consumers. This could be implemented as a registry but that limits the wire format to a push or pull mechanism. If we want to support multi-cast and broad-cast (think how Blue tooth components advertise to each other) then a registry or directory may not be the ideal mechanism. A P2P broadcast protocol does have advantages in certain implementations. Now - that is the reference model answer. If you ask the question in the context of web services or ebXML, then the answer may be different. ebXML does require a registry currently, according to the architecture. This in itself may be wrong and not applicable to all ebXML implementations. It is possible to have a CPP on a file server somewhere rather than a full blown architecture including a registry. IMO - the current architecture should be updated to reflect this. Also - web services do not require the use of a UDDI directory. You can simply analyze WSDL instance files to determine binding parameters to invoke/consume a service. There are 5 basic components of SOA that we have identified at this time, although at an abstract level, there may only be 4 since the contract details may be deemed part of the service specification (description). What are the elements of the SOA RM? · Services · Advertisement & Discovery Mechanism · Specification of services (including security parameters & constraints, reusability & repurpose-ability). · Specification of associated data model. (optionally) an explicit contract offer Q: What is the SOA Reference Model? A: The SOA reference model is a framework for understanding significant relationships among the entities in a service oriented environment, and for the development of consistent standards or specifications supporting that environment. The SOA reference model is based on a small number of unifying concepts and may be used as a basis for education and explaining standards to a non-specialist. Q: How does the SOA RM relate to the pattern concept? A: SOA RM IS A PATTERN! Q: How does “infrastructure” fit into the reference model? A: The reference model’s purpose is to act as a guide for those designing an SOA infrastructure. Q: Does the SOA reference model require definition of core infrastructure? A: No. Q: What is a service? A: A service is a contractually defined behavior that can be implemented and provided by a component for use by any component solely based on the contract. Q: What is advertising? A: Service must somehow communicate its service descriptions in a manner that is accessible to potential consumers. Q: What is discovery? A: A potential consumer obtains information about the existence of a service and its applicable parameters / terms. Discovery does not constitute authorization to execute against the service. Q: What does specification of services mean? <>A: Technical parameters, constraints, policies that come together to define terms of invocation. The latter may also include the contract so we still have lots of analytical work to do. Duane Nickull -- *********** Senior Standards Strategist - Adobe Systems, Inc. - http://www.adobe.com Vice Chair - UN/CEFACT Bureau Plenary - http://www.unece.org/cefact/ Chair - OASIS eb SOA TC - http://www.oasis-open.org/committees/tc_home.php?wg_abbrev=ebsoa ***********
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