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RE: The purpose of bindings

From: Glen Daniels <gdaniels@sonicsoftware.com>
Date: Fri, 9 Apr 2004 12:36:06 -0400
Message-ID: <80A43FC052CE3949A327527DCD5D6B2728003C@MAIL01.bedford.progress.com>
To: "Jeff Mischkinsky" <jeff.mischkinsky@oracle.com>
Cc: "WS-Description WG" <www-ws-desc@w3.org>


+1 to Jeff's comments.

--Glen

> 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.
> 
> Hi,
>    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.
> 
> HTH,
>    jeff
> 
> 
>> 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. 
>> 
>> Anne
>> 
>> 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 bindings. 
>>> 
>>> 
>>> 
>>> 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 12:36:49 GMT

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