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Re: The purpose of bindings

From: Anne Thomas Manes <anne@manes.net>
Date: Fri, 09 Apr 2004 11:10:35 -0400
Message-Id: <6.0.1.1.2.20040409110153.040d0100@localhost>
To: Jacek Kopecky <jacek.kopecky@systinet.com>, WS-Description WG <www-ws-desc@w3.org>

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.

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 
Received on Friday, 9 April 2004 11:11:54 GMT

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