W3C home > Mailing lists > Public > www-ws-desc@w3.org > November 2002

Re: A proposal for supporting property binding

From: FABLET Youenn <fablet@crf.canon.fr>
Date: Mon, 04 Nov 2002 17:24:51 +0100
Message-ID: <3DC69F53.7050601@crf.canon.fr>
To: Amelia A Lewis <alewis@tibco.com>, Jean-Jacques Moreau <moreau@crf.canon.fr>
CC: www-ws-desc@w3.org

>On reviewing the proposed outline (in your original response, which set
>forth a schema-pattern for these things), so that the email binding
>could use that model, I discovered the property definition section.  I
>think that these are not necessary; only bindings of properties are
>necessary, their characterization in XML is not.  I can expound on that
>if you wish (it took more senior architects here a couple of days to
>convince me that an XML description of a feature, while possible, is
>either superfluous or insufficient, but that seems to be the case).

I am not sure exactly why  there is no good in a characterization of 
properties in XML/XML-Schema.
I agree that it is not feasible to build a parser that will implement a 
feature from an xml description.
However an xml description of a feature might be useful for other 
purposes: it allows for instance to say how are implemented features.
Let's have a signature feature with an algorithm property. This property 
tells the server which algorithm (SHA/RSA, MD5/RSA....) to use in the 
signature process. It might be useful for the server to advertise which 
algorithms it supports.
A general xml description of the algorithm property would be for instance
<property name="algorithm" xsi:type="xsd:string"/>
There is no "useful" information in this description since the client 
has to implement this feature to use it..
The xml description of the server would be something like:
    <property name="algorithm">
        <xsd:restriction base="xsd:string">
            <xsd:enumeration value="SHA/RSA"/>
            <xsd:enumeration value="MD5/DSA"/>
In this case, the server clearly indicates how to use the feature (I 
understand SHA/RSA and MD5/DSA signatures).
An xml description of a feature is therefore useful when using a subset 
of a feature and /or when using an extensible feature.
Schema validation tools can test whether the values that are assigned to 
features in the wsdl file are allowed by these features.
It is also interesting to note that feature schemas are already almost 
written for most of (all ?) known features. Why not reusing them ?

Also to be noted that this mechanism (plus the use of a wsdl:protocol 
element that is referenced from the wsdl:binding) can be useful for 
interoperability purposes: an organisation  can produce an XML profile/a 
protocol description with all the necessary features that must be 
supported plus the way they must be implemented (like use HTTP + support 
feature FOO + the property POO of FOO must have one of these values...)

Received on Monday, 4 November 2002 11:25:43 UTC

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