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Subject: Re: [sca-assembly] Summarizing the state of ASSEMBLY-235
- From: Mike Edwards <mike_edwards@uk.ibm.com>
- To: OASIS SCA Assembly <sca-assembly@lists.oasis-open.org>
- Date: Thu, 17 Feb 2011 15:47:13 +0000
Eric,
I'm sorry that this has been left lonely
and uncommented on. We're clearly enjoying event processing too much.
There is a comment inline. I think
that it would also help if you could describe at least one concrete example
of
a mapping that you'd like us to support.
Yours, Mike
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Dr Mike Edwards
| Mail Point 146, Hursley
Park
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STSM
| Winchester, Hants SO21
2JN
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SCA & Services
Standards
| United Kingdom
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Co-Chair OASIS SCA
Assembly TC
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IBM Software Group
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Phone:
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Mobile:
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e-mail:
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From:
| Eric Johnson <eric@tibco.com>
|
To:
| OASIS SCA Assembly <sca-assembly@lists.oasis-open.org>
|
Date:
| 15/12/2010 01:26
|
Subject:
| [sca-assembly] Summarizing the state
of ASSEMBLY-235 |
In a previous
email I proposed something similar to the following
change. This time I tried to be more precise, so that this is more
than just directional.
Change 6.2.1 #6, 6.2.2 #6, and 6.2.3 #6 in the following pattern:
Replace text that reads:
"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.
For checking the compatibility of 2 local interfaces which are in different
interface languages, the method of checking compatibility is defined by
the specifications which define those interface types, which must define
mapping rules for the 2 interface types concerned."
... with the following ...
"The interfaces, whether local or remotable, must map onto a common
interface description language, and that the two interfaces are compared
on the basis of that common interface description language. See section
Comparing Interface Descriptions of Different Types for a discussion."
... and then add a section 6.2.4:
6.2.4 Comparing Interface Descriptions Of Different Types
A variety of interface descriptions for services exist. Examples of well-known
types include XML-RPC, CORBA, REST, WSDL 1.1, WSDL 2.0, SNMP, and JMX.
Implementations ought to use the interface type mappings that best
preserve the semantics of the underlying exchange.
To establish a basis of comparison between two different interface definition
types, the implementation has to map one or both of the interface descriptions
to a common definition type. The implementation has to identify that
common type, and ought to keep possible conversion errors to a minimum
by eliminating spurious conversions, and selecting the form with the best
semantic relevance. For example, if one interface description type
maps to WSDL 1.1, and the other interface type is WSDL 1.1, then the SCA
implementation ought to compare on the basis of WSDL 1.1. When neither
interface type can directly convert to the other interface type in question,
and conversion to WSDL 1.1 is possible, implementations SHOULD map both
interface descriptions to WSDL 1.1.
<mje>
The question is - who defines
the mapping?
If I've got <interface.x.../>
and <interface.y.../>, who says what the mapping between x and y
is for some actual interfaces of each type?
Is this to be described
in either or both of the specifications for x and y - or is it simply left
to the SCA runtime to pick what it pleases?
I am somewhat concerned
by the potential for lack of portability here, if runtimes are left free
to choose what they will. I think the current
formulation of the SCA
spec aims to get consistency between runtime implementations. How
can we ensure this for the relaxed case?
</mje>
Justifications for the above:
The specification already allows for the use of remotable interfaces defined
using something other than WSDL 1.1. For example, a Java JMX interface
description can be marked remotable. The existing rules only reject
the notion of compatibility when the two interfaces being compared are
of different types, but don't actually reject the notion of remotability
being applied to said interface types. As a possible example, XML-RPC
can be represented by a variety of description languages.
The above change relaxes a constraint that imposes on an implementation
the need to declare incompatibility where none may exist. Specifically,
by allowing additional scenarios to interoperate, the composers will be
able to express interface definitions that more closely align to their
implementation language, and the semantics of the underlying problem, rather
than by restricting themselves to the subset of the interface description
that maps to WSDL 1.1.
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
3AU
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