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RE: Action 2003-01-21 for Umit

From: Jacek Kopecky <jacek@systinet.com>
Date: 03 Mar 2003 14:50:01 +0100
To: Martin Gudgin <mgudgin@microsoft.com>
Cc: Umit Yalcinalp <umit.yalcinalp@oracle.com>, WS Description WG <www-ws-desc@w3.org>
Message-Id: <1046533100.1023.26.camel@localhost.localdomain>

> I think anything which is of type xsd:base64Binary or xsd:hexBinary can
> be serialized as an attachment. The binding would specify such a
> serialization for a given element using either a SCD or an XPath.

What I don't get is why these two XS simple types are so special. Why
can't I have a decimal or a string attachment? I understand that a
decimal has few or no problems with being transferred in XML (characters
permitted in a decimal don't cause any XML escaping), but data size
growth caused by XML escaping is only one of the reasons for
attachments, isn't it?

Some of the reasons for attachments (I'm sure these are not all of
them): 

      * XML parsing costs
      * data size growth due to XML escaping (like &lt; or base64)
      * process streaming (the rest of the message is available before
        the attachment is, so I can send the attachment after the XML
        message and thus improve performance)

I'm nervous about validation, too, because if a base64Binary element is
actually sent as an attachment, the attachment identifier has to be in
the message somewhere - where is it? An attribute on the element is the
logical place but it wouldn't validate.

XML Schema is a language for the description of an infoset structure. I
think the Attachment Feature Task Force of the XMLP Working Group has a
proposal that makes the attachments parts of the message infoset - how
does this relate to XML Schema usage? Would XML Schema be able to
describe an infoset with attachments?

Anyhow, I believe we want to allow different type systems (and schema
languages) to be used with WSDL. I trust the proposal for removing
message doesn't change that. So, can we think of wsdl:message as a
simplistic type system allowing by design combining other type systems
in parts of one piece of data (the message)? Is it not a useful one?

I don't know how XML Schema supports other type systems (like saying
this infoset item here is actually described using a different schema
language). The parenthesized example leads me to think that because
other type systems don't need to care about infoset, XML Schema is
actually not combinable with such type systems.

I'd keep the message, I find it useful at least in combining different
type systems.

Best regards,

                 Jacek Kopecky
                 Systinet Corporation
                 http://www.systinet.com/
Received on Monday, 3 March 2003 08:50:08 GMT

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