Re: [xsl] Where is the DTD for XSL

Subject: Re: [xsl] Where is the DTD for XSL
From: "G. Ken Holman" <gkholman@xxxxxxxxxxxxxxxxxxxx>
Date: Tue, 02 Sep 2003 07:56:04 -0400
At 2003-09-02 16:55 +0530, Sanghamitra Das wrote:
When we write an xsl, we get some error if the XSL is not proper. How the
validation actually happens?

The XSLT processor performs validation on the input XSLT stylesheet.

Where is the DTD for XSL?

There is no DTD for XSL.

Can any one tell me the logic behind the process.

DTD syntax is not expressive enough to describe all the required constraints for an XSLT stylesheet. The XSLT processor has to work on the entire document anyway in order to complete its task, so it is in a position to do all of the required validation algorithmically instead of relying on a declarative expression in an external grammar. Everyone's result vocabulary is potentially unique and there is no way a standards committee could constrain everyone's possible outputs."; This link has the DTD.

This is not true, the link has a non-normative DTD fragment used to help a reader understand the gist of the requirements, but the collection of parameter entities supplied must be tailored to your result vocabulary in order for it to be utilized as a standalone grammatical expression of an instance of a stylesheet.

Even then, it is impossible to express all of the constraints using DTD semantics. Take, for example, <xsl:template>. This element requires either the name= attribute, the match= attribute, or both of these attributes, but not neither of these attributes. This cannot possibly be expressed in the DTD semantics for a document model.

But in the namespace we use this <xsl:stylesheet
xmlns:xsl="";  version="1.0">

Namespaces have *nothing* to do with document models and are *only* used to distinguish constructs from the XSLT vocabulary from constructs of other vocabularies you utilize in your stylesheet. There is no other purpose for namespaces than vocabulary distinction in XML instances.

The question remains, even if it *were* possible to express all of the constraints in DTD semantics (which isn't possible), why is an external standalone grammatical expression of the XSLT document model important to you when the XSLT processor is already fulfilling the constraint validation checking on your stylesheets?

I hope this helps.

.......................... Ken

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