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Re: Validate **against** a schema OR validate **with** a

• From: rjelliffe@a...
• To: "xml-dev@l..." <xml-dev@l...>
• Date: Fri, 23 Jan 2009 15:04:11 +1100 (EST)

> Defaulting values came from SGML days and DTDs..  So it's been around for
> a
> while.  Many folks have wanted the validation and augmentation steps
> separate though no real progress on that.

Adding default information and other properties is a very respectable
thing for a schema language to do, IMHO.

The difficulty is when 1) there is no processing model that guarantees it
will happen (with SGML and perhaps XML entities the augmentation is
required), and 2) when the augmentation does not have a natural or formal
XML form and so requires a change in technology. Unreliability and
uselessness are rarely a sweet spot.

The dis-integrated committee processes at W3C makes it difficult to get
any resolution of these, it seems to me. I am not sure that the
(numerical, at least) dominance of database company reps and semantic web
people on the W3C TAG helps put it on the radar either.

What is happening, I think, is that because of the complexity of XSD, the
unreliability of PSVI augmentation, and the lack of PSVI-in-XML,
developers end up using XSLT to do defaulting, either by preprocessing or
(probably more often) by copying the defaulting code in each transform
they write. As far as defaulting goes, XSD has been a major step backwards
for markup processing, but I suppose it is an issue essentially irrelevant
if you assume you have a DBMS in the picture.

Cheers
Rick Jelliffe

• Follow-Ups:
  • RE: Validate **against** a schema OR validate **with** a schema?
    • From: "Michael Kay" <mike@s...>
  • Re: Validate **against** a schema OR validate **with** a schema?
    • From: DavePawson <davep@d...>