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Perhaps the expression "single step" was misleading, as what I meant was that the validation of the input against a W3C XML Schema can be done during the XSLT/XQuery processing using a Schema-aware processor, so that you reduce the number of individual steps in the validation process by one. As for how you use XSLT/XQuery to flag "Schematron level" validation failures, the situation is less clear and straightforward. With XSLT, you can use <xsl:message> to terminate the script, but that means you only get to report one issue, and one-at-a-time reporting and correction of issues is a painful thing for users (as users of older Borland or Altova products would well remember). On that basis, I prefer to use the XSLT/XQuery to write out an XML report of errors/warnings (aking to what Schematron does, although the Schematron XML reporting format isn't sufficient for my needs, as well as being all but undocumented). I then check that XML output and throw an exception as appropriate if there are errors. I wouldn't be using output validation except as a way to check that my error report has been correctly constructed by my script. Cheers, Tony. On Thu, 09 Aug 2007 11:55:30 +0100, Andrew Welch <andrew.j.welch@g...> wrote: > On 8/9/07, Anthony B. Coates (XML-Dev) > <abcoatesecure-xmldev@y...> 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 ;-) > -- Anthony B. Coates Senior Partner Miley Watts LLP Experts In Data UK: +44 (20) 8816 7700, US: +1 (239) 344 7700 Mobile/Cell: +44 (79) 0543 9026 Data standards participant: genericode, ISO 20022 (ISO 15022 XML), UN/CEFACT, MDDL, FpML, UBL. http://www.mileywatts.com/
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