W3C home > Mailing lists > Public > xml-dist-app@w3.org > September 2001

Re: why no doc type declaration and PIs in SOAP?

From: <Noah_Mendelsohn@lotus.com>
Date: Fri, 21 Sep 2001 10:57:44 -0400
To: francis@redrice.com
Cc: "Champion, Mike" <Mike.Champion@SoftwareAG-USA.com>, xml-dist-app@w3.org, xml-dist-app-request@w3.org
Message-ID: <OFF5CB1E1E.588D6EBB-ON85256ACD.006D87D7@lotus.com>
Francis Norton writes:

>> Why do you exclude the payload? Are SOAP payloads 
>> allowed to contain DTDs and PIs?

As I said in my previous note, having a way to allow a payload to carry an 
entire XML document would be a good thing.  Bad news:  XML itself doesn't 
allow it, one of the primary failings of XML IMO (a hierarchical format 
that can't contain itself.)  Why?  Well among other reasons, you can't 
have multiple internal subset DTD's in an XML document.  There's no 
scoping mechanism for them.   You might also want to switch encodings 
(e.g. a schema in UTF8 describing a document in BIG5, both in the same 
envelope.)  General entities can't have conflicting names in the same 
document, etc., etc.   So, a good goal, but if we don't revise XML itself 
we will have to either use encoding tricks, something like 
SOAP+attachments, etc.  You cannot in general carry a complete XML 
document, or even just an extra payload-oriented internal subset DTD, 
within what is otherwise an XML SOAP envelope document.

BTW:  the statements about schema are true.  It doesn't let you declare 
entities.  As I said in my previous note, entities are useful, but they do 
have performance implications.  I'm not convinced that for applications 
like web services messaging they are worth the cost.

Noah Mendelsohn                                    Voice: 1-617-693-4036
Lotus Development Corp.                            Fax: 1-617-693-8676
One Rogers Street
Cambridge, MA 02142
Received on Friday, 21 September 2001 11:06:11 UTC

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