Re: [xml-dev] A single, all-encompassing data validation language - good

["Andrew Welch" <andrew.j.welch@gmail.com>]

On 8/9/07, Anthony B. Coates (XML-Dev) <abcoatesecure-xmldev@yahoo.co.uk> wrote:
> I was not in any sense confused.  Perhaps you would care to re-read what I
> wrote.  Cheers, Tony.

Ok, sorry if I suggested you were and you weren't - you said:

====
Schematron is a useful complement, but in the past, I've always found that
it, too, was too limited for what I needed, and so I found myself using
XSLT instead.  Recently I've been using XQuery, which I think has a lot to
recommend it as a language for encoding a layer of data validation that is
at a level above what the schema languages do.  The integration of both
XSLT 2.0 and XQuery (in some implementations) with W3C XML Schema means
that you can do this level of data validation in the same single step as
the Schema validation, which can be helpful.
====

and I enquired which implementation you were referring that would
allow you to "do this level of data validation in the same single step
as
the Schema validation", which you replied:

====
I've seen it demonstrated using the commercial version of Saxon
(www.saxonica.com).  I believe the Altova XML Query Processor also has
support, although it may not be fully debugged yet (but is said to be
making progress).  I'm sure there are others, but I don't know which
ones.  The W3C list of XQuery implementations is here:

http://www.w3.org/XML/Query/#implementations

but this doesn't tell you which implement Schema-awareness.  I know that
some implementations apparently do not intend to implement it.  I'm sure
the vendors of XQuery processors that are Schema-aware won't be shy to
post a note to that effect on this list, but it would be helpful if the
W3C page captured that information, which it doesn't right now.
====

...which made me think you were just talking about schema aware
transforms/XQueries.

The only way I can think of using an SA processor with XSLT/XQuery to
"validate" the source XML *and* apply some extra checks using
XSLT/XQuery in a  *single step* is to use input validation (or copy
the entire input to the result and use result validation for those
processors that only support result validation) along with the kind of
checks that would cause the validation to fail:

<xsl:if test="$foo > $bar">
  <xsl:message terminate="yes">Foo should never be greater than
Bar</xsl:message>
</xsl:if>

Without terminating at that point you'd need to output something to
the result and then have an extra step to check the result (which
means a proprietary output format and some code to check the output,
but you'd be able to get the full list of failures rather than just
the first.)

However, using input validation with a transform that terminates when
a check fails is an appealing option, and available now...

(I'm sure that's what you meant ;-)

-- 
http://andrewjwelch.com