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Subject: Re: [sca-assembly] NEW ISSUE (v1.2): Remotable interface compatibilityshould not be restricted to a WSDL 1.1 mapping


Hi Bryan,

Yes, thanks for throwing that information into the mix.

I note, from the current CD05 rev1 draft, lines 2787, 2788:
"An interface is defined in terms of a WSDL 1.1 portType with the arguments and return of the service operations described using XML schema."  (Hmmm, that "s" in "schema" should be capitalized - editorial nit.)

While this statement does not appear to influence any normative constraints, it certainly aligns with the expectations that everyone brings to bear on WSDL 1.1.

If you allow for the notion that WSDL 1.1 with alternate type systems aligns with SCA Assembly's remotable concept, then we *definitely* need more text around how type systems should be determined to be compatible.  In a sense, you're just "squeezing the balloon", in that the problem pops up in a different place, but has exactly the same implications.

Should we change the issue in question to be:
"Remotable interface compatibility should not be restricted to a WSDL 1.1 mapping, nor should it be restricted to WSDL 1.1 using XML Schema."

... or maybe that's two issues?

-Eric.

P.S. http://www.w3.org/TR/wsdl20-altschemalangs/

On 07/16/2010 10:57 AM, Bryan Aupperle wrote:
OF1FB3C125.FD6C460C-ON85257762.00607CD7-85257762.0062ADD4@us.ibm.com" type="cite">I realize that we have not opened this issue yet. but I recognize the validity of allowing transport representations other than XML documents.

Having said that, there seems to be an assumption here that WSDL 1.1 requires a XML 1.0 data format and the use of the XSD type system.  This is not correct.  WSDL 1.1 explicitly allows for other type systems and also notes that the XSD type system can be used even if the data format is not XML 1.0.  I am not sure if the WS-I Basic profiles require either the use of the XSD type system or an XML 1.0 data format, but I do not believe that the Assembly spec currently says anything about WSI-Basic Profile compliance.

An excellent view of how a view of the XSD type system can be used with other data formats is defined in the Data Format Description Language (DFDL) specification (being defined by an Open Grid Forum WG - http://forge.gridforum.org/projects/dfdl-wg/)   The public review draft is here: http://www.ogf.org/Public_Comment_Docs/Documents/2010-03/draft-gwdrp-dfdl-core-v1.0.pdf  DFDL allows data to be mapped between native formats (binary, textual) and information sets – and thus XML.  The information set is described using XSDL types and annotated constructs. The data can contain any character in ISO 10646, including those not legal in XML documents. In addition to facet validation, assertions can be added to test data during parsing. Allows data from native representation to be excluded from the information set, information set values to be calculated on parse and native representation data to be calculated on generation.

I am not positive that DFDL will cover all of the use cases Eric notes, but it would appear that:
1) A number of the are currently possible
2) The assembly spec could be clearer and more robust in the treatment of this topic.

Bryan Aupperle, Ph.D.
STSM, WebSphere Enterprise Platform Software Solution Architect
WW Center of Excellence for Enterprise Systems & Banking Center of Excellence Application Integration Architect

Research Triangle Park,  NC
+1 919-254-7508 (T/L 444-7508)
Internet Address: aupperle@us.ibm.com



From: Mike Edwards <mike_edwards@uk.ibm.com>
To: OASIS SCA Assembly <sca-assembly@lists.oasis-open.org>
Date: 06/29/2010 05:14 AM
Subject: Re: [sca-assembly] NEW ISSUE (v1.2): Remotable interface compatibility should not be restricted to a WSDL 1.1 mapping






Logged as:
http://www.osoa.org/jira/browse/ASSEMBLY-235

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


From: Eric Johnson <eric@tibco.com>
To: OASIS SCA Assembly <sca-assembly@lists.oasis-open.org>
Date: 28/06/2010 18:56
Subject: [sca-assembly] NEW ISSUE (v1.2): Remotable interface compatibility should not be restricted to a WSDL 1.1 mapping






Target: sca-assembly-1.2-spec-wd01.doc

Title: Remotable interface compatibility should not be restricted to a WSDL 1.1 mapping

Description:

The latest version of the Assembly specification (sca-assembly-1.1-spec-cd05), in section 6.2, defines interface compatibility in section 6.2.1, item #6 "for checking the compatibility of 2 remotable interfaces which are in different interface languages, both are mapped to WSDL 1.1 (if not already WSDL 1.1) and compatibility checking is done between the WSDL 1.1 mapped interfaces."

There are various reasons why this will fall over and not behave as expected.

False positives:
  • Some other interface kind may impose data type semantic restrictions which are not apparent in a WSDL 1.1 representation.  WSDL 1.1 uses XML Schema 1.0 types for its representation of data.  Unfortunately, there are limitations here, where XML Schema largely focuses on the syntactic representation, and not as much on the semantic values.  Some random examples:
    • all odd numbers/all even numbers
    • string validation via regular expressions, where some semantic is required on a portion of the string.  Example - credit card numbers
    • string contents - XML Schema "string" type allows for a subset of all possible characters.  This means that certain characters cannot be represented in XML Schema representations, and must be somehow mapped.
  • Object networks - representing a network of objects serialized to XML, certain objects should be serialized at most once, and then referenced.  Creating and enforcing the linking of representations is at best an imperfect alignment, as there are numerous ways that this can be accomplished, depending on the type of the object network.  Unfortunately, something conforming to the XML Schema requirements could easily not align on the semantic requirements, either in generating a request, or receiving a response.
False negatives:
  • Intrinsic to mapping to WSDL are choices about how that mapping might be done.  For example, implementations might map JMX to WSDL in myriad ways.  Forcing the consumer and provider to do so in a way that offers up a WSDL 1.1 mapping as part of the component type could lead to a declaration of "incompatible" even where the JMX interfaces are, in fact compatible (albeit, at runtime, the implementation of the JMX conduit must be shared)
  • Bad compromises - certain existing bindings (binding.jms) allow for possibility of sending Java Objects via JMS.  To not be able to call these bindings remotable is a mockery of the notion of "remote", however, forcing a mapping of a generic Java Object to some XML representation will have "binding" trade-offs.  Implementers will then have to invest time to "maximize compatibility", whereas if they simply used existing interfaces compatiblity would simply be there.
(Partial) Proposal:

Remoting compatibility should not be restricted to WSDL 1.1 mappings.  Interface type definitions ought to be allowed to at least define a compatible relationship with themselves.

-Eric.






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