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Subject: RE: [soa-rm-ra] about NCOIC Service Interface Pattern
+1 An example of a stable interface is one we specified for a Deliver component: inputs are the package to deliver, the address where to deliver, and a properties set that can convey the required conditions for delivery. The property set could (details still being worked) conform to an XML schema (or other formalism) and would begin with something identifying the schema, etc. being used. If new conditions are required over time, you update the schema. It is up to the receiver to adequately understand and comply with the properties or return appropriate faults if that is not possible. Note, this is completely independent of SLAs, governance policy, etc. Such things may have bearing on how a conformant service is designed and operated, but this is separate from the design and implementation of the stable interface. Ken --------------------------------------------------------------------------- Dr. Kenneth Laskey MITRE Corporation, M/S H305 phone: 703-983-7934 7515 Colshire Drive fax: 703-983-1379 McLean VA 22102-7508 From: mpoulin@usa.com [mailto:mpoulin@usa.com] Rex, this is so hot topic that I could not resist looking into it briefly. I read, probably 1% of the material but it's happened that Interface Stability just jumped into my eyes: 2.4.9 Interface Stability {SOA}[1]To achieve interface stability through design, the following SOA structure requirements apply: a. Service Level Agreements (SLA)s or equivalently named contractual instruments shall contain Explicit Operational Agreements. b. Explicit Operational Agreements shall contain interface definitions. c. Explicit Operational Agreements should contain a governance policy d. The authentication and authoritization process for who can examine published contracts shall be standards based.. e. Interface artifacts shall be published in a registry/repository or other object, e.g., ESB. f. Interface Definitions shall be standards based, e.g., WSDL, XSD, etc. g. The SLA shall contain performance characteristics associated with each interface. h. SLAs shall be maintained between the Provider and individual Consumers or classes of Consumer i. Versioning processes may be contained in a separately defined governance process. Governance principles are described in the NCSF. A NCOIC governance pattern is under consideration. To my taste, copied content has almost nothing to do with "Interface Stability". I think that stability of service interface is about how the interface can work in the changing environment, changing behaviour model and related messages. For example, Interface Definitions shall be standards based, e.g., WSDL, XSD, etc" does not contribute into the stability, IMO, because someone may (should not be restricted from) publish (ing) a non-standardised but immutable (100% stable) interface. Moreover, common (not thought through) use of WSDL leads to constant changes if the interface, i.e. minimal stability. In the essence, it is not a standardisation that important, but the usability pattern is important. And the latter has escaped aforementioned list. An example of interface stability: 'adding or removing data elements of the exchange messages should not result in the change of interface'. I can say the same thing regarding the operations and use WSDL (in a smart way) to implement this. Anyway, thank you very much for such interesting material. - Michael -----Original Message----- Hi Guys, Hi Folks, I will have a conflict of meetings today: I will be able (now) to participate in the first and the last 30 min time-windows only. Please, plan my presentation on the Management Model accordingly. Sorry, - Michael -- Rex Brooks President, CEO Starbourne Communications Design GeoAddress: 1361-A Addison Berkeley, CA 94702 Tel: 510-898-0670 [1] SOA (Service Oriented Architecture), NC(net centric), & SW(software) are solution categories. They are used here to map the solutions in sections 2.4 and 2.5 to these categories. See Appendix C, section 5.3 for a summary of this mapping. |
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