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Re: The purpose of bindings

From: Jeff Mischkinsky <jeff.mischkinsky@oracle.com>
Date: Fri, 09 Apr 2004 08:59:11 -0700
Message-Id: <>
To: Anne Thomas Manes <anne@manes.net>, Jacek Kopecky <jacek.kopecky@systinet.com>, WS-Description WG <www-ws-desc@w3.org>

At 08:10 AM 4/9/2004, Anne Thomas Manes wrote:

>I haven't been involved in the conversation, but it occurs to me that it 
>isn't appropriate to define authentication, authorization, 
>confidentiality, etc requirements and constraints in an interface definition.
>An interface is a *reusable*, abstract definition. Any number of service 
>providers should be able to implement an interface. Authentication, etc, 
>constraints apply to a specific implementation of an interface.

   I think I have partially different view. I start from WSDL is the 
contract. The contract may include the kinds of constraints that are 
mentioned above. If  an authentication constraint, e.g., is included as 
part of the interface definition, then all the bindings need to respect it.
I have a hard time with the notion of "implementation-specific" as having 
an absolute meaning. In my experience, one person's 
"implementation-specific" information is another person's interface 
information. I think it depends upon where you sit.

Note: I'm not saying that is inappropriate to have implementation-specific 
information. Just that it is an application design choice at what level in 
the abstract/concrete binding/implementation hierarchy one associates 
various constraints.


>Likewise, a binding is a *reusable*, concrete mapping of an abstract 
>interface to a set of protocols. Any number of service providers should be 
>able to implement a binding. Hence you really shouldn't specify 
>implementation-specific information in a binding.
>Information that applies to a specific implementation should be defined in 
>a separate definition.
>At 03:57 AM 4/9/2004, Jacek Kopecky wrote:
>>Hi all,
>>during yesterday's call we discovered it may be unclear what the purpose
>>of bindings is, which makes very fuzzy the line of what should be in a
>>binding and what should be in an interface.
>>Here's my take:
>>In WSDL, an Interface describes the application-level interface with all
>>information necessary for the application. A Binding describes how the
>>interface is realized on the wire.
>>The main part of what the interface describes is the operations, message
>>formats and exchange patterns. Additionally, using features (or
>>extensions like policy or whatnot) an interface may specify other
>>constraints, e.g. the necessity of authentication, confidentiality of
>>communication, transactionality etc. Finally, an interface may describe
>>important properties of operations and messages, e.g. web safeness or
>>cacheability of results.
>>A binding must be able to transfer the messages of its interface's
>>operations, following the message exchange patterns, to an endpoint.
>>Additionally, a binding must realize all features that an interface
>>mandates and it must follow all constraints specified in the interface,
>>e.g. the HTTP binding may realize communication confidentiality by
>>mandating the use of HTTPS, or the SOAP binding may realize
>>confidentiality by mandating the use of XML Encryption in the messages.
>>Finally, a binding may take advantage of the properties described in its
>>interface, for example by allowing opportunistic pre-invocation of
>>web-safe operations or by allowing caching of cacheable results.
>>To summarize, the boundary is in the application - information important
>>for the application goes into interfaces, implementation details go into
>>My on-line presence may be very sparse next week, so please be patient
>>if any clarifications are necessary.
>>Share and enjoy,
>>                    Jacek Kopecky
>>                    Systinet Corporation
>>                    http://www.systinet.com/
>Anne Thomas Manes
>VP & Research Director
>Burton Group

Jeff Mischkinsky                      jeff.mischkinsky@oracle.com
Consulting Member Technical Staff     +1(650)506-1975
Director, Web Services Standards      500 Oracle Parkway M/S 4OP9
Oracle Corporation                    Redwood Shores, CA 94065
Received on Friday, 9 April 2004 11:57:02 UTC

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