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Subject: Re: [sca-assembly] NEW ISSUE (v1.2): Remotable interface compatibilityshould not be restricted to a WSDL 1.1 mapping
- From: Mike Edwards <mike_edwards@uk.ibm.com>
- To: OASIS SCA Assembly <sca-assembly@lists.oasis-open.org>
- Date: Tue, 29 Jun 2010 10:13:03 +0100
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.
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6
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