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RE: SOAP Encoding: Default values

From: Andrew Layman <andrewl@microsoft.com>
Date: Sat, 16 Feb 2002 20:02:05 -0800
Message-ID: <C3729BBB6099B344834634EC67DE4AE102623D46@red-msg-01.redmond.corp.microsoft.com>
To: "XML Protocol Discussion" <xml-dist-app@w3.org>
The discussion of default values in SOAP encoding is an error.  It was a
mistake to include it and we would be well advised to remove it.  This
is not to say that default values are a bad idea per se, but rather that
they occur at a higher semantic level than SOAP serialization. SOAP
serialization rules have to do with the transformation of data
representations between DLG/structs and XML syntax.  The idea of default
values appears only in terms of the interpretation of the meaning of the
data so represented.

However, the relation between absence and nulls has historically not
been subject to broad consensus, and this means that we cannot make the
specification better than it is on that subject.  The lack of broad
agreement is true, not only within SOAP discussions, but in the much
longer history of databases and programming languages generally.  For
that reason, unless the XML Protocol WG wants to solve a problem that
has eluded consensus for thirty-odd years, the rules must state simply
that accessor absence may or may not equate to a null, and what a null
means, if anything, is determined by a semantic level higher than the
SOAP encoding.  Application metadata may, of course, provide more
specific answers for any particular structure.
-----Original Message-----
From: Martin Gudgin [mailto:marting@develop.com] 
Sent: Friday, February 15, 2002 9:00 AM
To: XML Protocol Discussion
Subject: SOAP Encoding: Default values

Section 3.6[1] of Part 2[2] states;

'An omitted accessor element implies either a default value or that no
value
is known. The specifics depend on the accessor, method, and its context.
For
example, an omitted accessor typically implies a Null value for
polymorphic
accessors (with the exact meaning of Null accessor-dependent). Likewise,
an
omitted Boolean accessor typically implies either a False value or that
no
value is known, and an omitted numeric accessor typically implies either
that the value is zero or that no value is known.'
I'm not convinced that this text is at all useful. It seems to say

'If the accessor isn't there, then any number of things might be
true...'
and doesn't say much about what those things might be.

What is the paragraph *supposed* to be saying?

Gudge

[1] http://www.w3.org/2000/xp/Group/1/11/10/soap12-part2.xml#IDA5FQLB

[2] http://www.w3.org/2000/xp/Group/1/11/10/soap12-part2.xml
Received on Saturday, 16 February 2002 23:03:08 GMT

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