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Subject: Namespace URI Design and Dereferencing

Dear SCA Technical Committees

In response to Sanjay's request for cross-TC consistency in Namespace URI Design & Dereferencing, please find attached the document discussed and agreed by the Steering Committee. It is now submitted back to each TC with a recommendation for adoption.

Graham J Barber,

OASIS OpenCSA Steering Committee Secretary & Vice-Chair,
Program Director, SOA Partnerships,
Internal:                              245702,  External: +44 (0)1962 815702
Secretary (Carol):          245395,                    +44 (0)1962 815395
Cellphone (Worldwide):                                    +44 (0)7880 734005

Subject: Namespace URI Design and Dereferencing
Title: Namespace URI Design and Dereferencing

Dear Steering Committee,

Following are some issues along with my proposed resolutions related to the namespace URI design and dereferencing that seem to apply to multiple OpenCSA TCs. I request the Steering Committee to deliberate upon these issues and recommend a set of resolutions for consistent adoption by all the OpenCSA TCs.


1>  What namespace URI format should be used by the different Open CSA TCs?
http://docs.oasis-open.org/OpenCSA/[defGroupName]/[yyyymm], the [defGroupName] stands for a group of semantically related definitions (e.g. SCA-Common to stand for the definitions commonly provided by the different OpenCSA TCs)  and [yyyymm] represents the year-and-month when the namespace URI came into existence (via a Committee Draft vote).

   OASIS guideline for URI design [1] recommends that the http scheme namespace URIs defined by the OASIS TCs to begin with:
http://docs.oasis-open.org/[tcShortName]/, where the [tcShortName] is the short name of the TC (e.g. SCA-Assembly, SCA-Bindings, etc). When more than one TCs provide definitions for the same namespace URI, there is a conflict as to which TC's short name should be used in the shared namespace URI. By design, the different OpenCSA TCs are going to produce artifacts that are closely related to each other, and therefore the guideline of compartmentalizing namespaces based upon TC names seems rather artificial and restrictive. This proposal  resolves the possible conflict by using short name of the member section (i.e.OpenCSA) instead of the short name of any TC in the URI design.

    The [defGrouptName] part of the URI can be used to compartmentalize namespaces based upon the semantic grouping of definitions. The definitions pertaining to any given [defGroupName] may be specified by more than one OpenCSA TCs.  For example, a namespace URI of http://docs.oasis-open.org/OpenCSA/SCA-Common/[yyyymm] may be defined by the SCA Assembly TC as well as the SCA Bindings TC, SCA Policy TC, etc.

    This proposal should also work for the case where an OpenCSA TC wants to design a namespace URI for its exclusive use. In this case, the TC should ensure that the value of the [defGroupName] is unique across all the OpenCSA TCs.

    We should consider the design and change of namespace URI as a separate issue from the versioning of the artifacts providing definitions for that namespace URI. Namespace URI is typically changed only when some definitions belonging to that namespace undergo backward incompatible changes. There are situations where the version number of artifacts may change but the namespace URI may remain the same. For example, a TC may decide to bump up the version number of a specification (e.g. use 1.5 instead of 1.1) to reflect some newly added changes, however if the changes are backward compatible then there is as no need to change the namespace URI.

    This proposal does not use the version number of artifacts providing definitions in the namespace URI design, but instead uses year and month of when the namespace URI was first adopted by the TC. If the namespace URI must undergo a change due to introduction of some non-backward compatible changes in the future, then the new namespace URI can reflect the year-and-month of its adoption by the TC. For example, if the SCA Assembly TC votes on its first Committee Draft in Nov 2007, the namespace URI for the assembly definitions would look like - http://docs.oasis-open.org/OpenCSA/SCA-Common/200711. Now, if the SCA Assembly TC later introduces some non-backward compatible changes and votes on a Committee Draft (say in Feb 2009) including those changes, then at that time a new namespace URI should be introduced which would look like - http://docs.oasis-open.org/OpenCSA/SCA-Common/200902

2> Should a namespace URI defined by the OpenCSA TCs be dereferenceable? If yes, what document should be returned when the namespace URI is dereferenced?

   Proposal: Any namespace URI defined by the Open CSA TCs should be dereferenceable, and a RDDL 2.0 document describing the namespace should be retrieved upon dereferecing the namespace URI. The RDDL 2.0 document at the namespace URI should include pointers to the various artifacts providing definitions for the namespace along with a brief introduction for each artifact, description of the namespace change policy, etc. As an example, we could refer some of the RDDL based namespace description documents created by the OASIS WS-RX TC [2].

    When definitions for a namespace URI are provided by more than one OpenCSA TCs, it is recommended that a single TC be identified as responsible for collecting references to the relevant artifacts owned by other OpenCSA TCs and creating a single information document for that namespace URI. Following the same example as used before, the information document for the namespace URI http://docs.oasis-open.org/OpenCSA/SCA-Common/[yyyymm]  should be owned by the SCA Assembly TC.

[1] http://docs.oasis-open.org/specGuidelines/namingGuidelines/resourceNamingV07.html#URI-Design

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