Re: [sca-assembly] [ASSEMBLY-195] import and export of the same namespacefor some testcases - PROPOSAL

[David Booz <booz@us.ibm.com>]

Jim,

Why do you assume that:

1. References to X from artifacts in B will resolve to the version of X
contained in C
2. References to X from artifacts in A will resolve to the version of X
contained in B

is a problem or is somehow an invalid or incorrect behavior for XML
artifacts?

Are you asking for additional functionality that would enable the OSGI uses
behavior when desired or necessary (similar to what we have in the SCA-J
specs)?

Dave Booz
STSM, BPM and SCA Architecture
Co-Chair OASIS SCA-Policy TC and SCA-J TC
"Distributed objects first, then world hunger"
Poughkeepsie, NY (845)-435-6093  or  8-295-6093
e-mail:booz@us.ibm.com


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  |Jim Marino <jim.marino@gmail.com>                                                                                                                 |
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  |OASIS Assembly <sca-assembly@lists.oasis-open.org>                                                                                                |
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  |03/18/2010 12:38 PM                                                                                                                               |
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  |Re: [sca-assembly] [ASSEMBLY-195] import and export of the same namespace for some testcases - PROPOSAL                                           |
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Comments inline.
On Mar 11, 2010, at 4:36 PM, Mike Edwards wrote:


      Folks,

      I propose that ASSEMBLY-195 is Closed with No Action

      ASSEMBLY 195 is concerned about testcase contributions which both
      import and export the same namespace.

      The claim is made that this behaviour is not explicitly defined in
      the Assembly specification and that it could
      lead to cyclic dependencies that would cause an error.

      However, I think that the Assembly specification is very clear about
      the meaning of import and export statements
      in Section 10.2.1 and there is a specific normative statement -
      ASM12023 - that indicates that any resolution of an
      artifact through an import statement must only be a one-deep search
      and that searches do not recurse through
      multiple levels of Contributions.

      As a result, cyclic dependencies of the kind mentioned in this issue
      are not possible.

      The claim that there needs to be a definition of an import/export
      pair in the Assembly spec is also unnecessary,
      since its meaning is well defined by ASM12023, with no ambiguity.


To be precise, the claim is that the Assembly spec is unclear about what
the runtime should do in this situation, not that it will lead to cyclic
dependencies. After rereading the paragraph cited, I still do not think
ASM12023 is clear on the appropriate behavior. As I mentioned in a previous
post, consider the following:

Contribution A ---(resolve {urn:foo}bar) ---> Contribution B ---(resolve
{urn:foo}bar) ---> Contribution C
   ---(resolve {urn:foo}bar) ---> Contribution C


Assuming contributions B and C both contain an artifact X in {urn:foo:bar}
and Contribution B imports and exports (resolve {urn:foo}bar), the
following may result:

1. References to X from artifacts in B will resolve to the version of X
contained in C
2. References to X from artifacts in A will resolve to the version of X
contained in B

Note that this behavior is different than OSGi and there are directives in
the former that can be used to avoid this from happening.

At a minimum, I think this needs to be clarified in the assembly spec as
users will invariably encounter this.  Import/export of the same namespace
is valuable in some situations but it needs specification.

Another way to look at this is: what normative statement is import/export
of the same namespace testing?

Jim




      Yours,  Mike.

      Strategist - Emerging Technologies, SCA & SDO.
      Co Chair OASIS SCA Assembly TC.
      IBM Hursley Park, Mail Point 146, Winchester, SO21 2JN, Great
      Britain.
      Phone & FAX: +44-1962-818014    Mobile: +44-7802-467431
      Email:  mike_edwards@uk.ibm.com






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