Re: [xsl] Why does this XPath expression work fine when run

You're confusing two things here.

Firstly, there's an absolute rule that an assertion can only look within the
subtree of the element on which it is defined. In other words, an assertion on
an element can make that element invalid, but it can't make other elements
invalid (other than containing elements of course). That's fundamental to the
XSD concept that the outcome of validation is not just a yes/no answer, but an
annotated document (PSVI) in which valid and invalid elements can be
distinguished.

Secondly, the spec says that by default, assertions can't see comments and
PIs. In other words, users can add comments and PIs to the instance without
worrying about whether the schema allows them. Again, that's based on a theory
about what comments and PIs are intended for. But here the spec relaxes the
rules, and says that "at user option" comments and PIs can be made visible to
assertions. Saxon provides such an option (--assertionsCanSeeComments:true on
the command line). But they're only visible if they're in the subtree of the
element being validated.

Michael Kay
Saxonica


> On 2 Dec 2019, at 18:12, Costello, Roger L. costello@xxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Thank you Graydon and Ken.
>
> If I understand correctly, you are saying that the XPath expression in an
XSD 1.1 assert may not reference comment fields. Correct?
>
> Okay, I will switch back to XSD 1.0 and express assertions using Schematron.
The XPath works fine in Schematron:
>
> <sch:rule context="xhtml:html/xhtml:head">
>    <sch:assert
test="xhtml:style/following-sibling::comment()[1]/starts-with(., '[if gte mso
9]>&lt;xml>')">
>        	Two comments may occur following the
> 	style element; they must contain a
> 	well-defined content
>    </sch:assert>
> </sch:rule>
>
> /Roger
>
> -----Original Message-----
> From: G. Ken Holman g.ken.holman@xxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
> Sent: Monday, December 2, 2019 12:50 PM
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx; xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject: [EXT] Re: [xsl] Why does this XPath expression work fine when run
inOxygen but fails when used in an XSD 1.1 assert element?
>
> The data model within which an assertion is evaluated is comprised only of
the element itself, not its siblings. You are looking at siblings.
>
> Per the specification:
>
> https://www.w3.org/TR/xmlschema11-1/#sec-cvc-assertion
>
> I hope this helps.
>
> . . . . . . Ken
>
> At 2019-12-02 17:27 +0000, Costello, Roger L. costello@xxxxxxxxx wrote:
>> Hi Folks,
>>
>> Below is a sample XHTML document. Immediately following the <style>
>> element is a comment. I want to ensure that the value in the comment
>> starts with this string:
>>
>>        [if gte mso 9]><xml>
>>
>> Using Oxygen, I ran the following XPath query (the <head> element is
>> the context node):
>>
>> *[local-name() eq
>> 'style']/following-sibling::comment()[1]/starts-with(., '[if gte mso
>> 9]>&lt;xml>')
>>
>> The result of running the query is:
>>
>>        true()
>>
>> Perfect!
>>
>> Next, I put the query into an XML Schema 1.1 assert element:
>>
>> <xs:assert test="*[local-name(.) eq
>> 'style']/following-sibling::comment()[1]/starts-with(., '[if gte mso
>> 9]>&lt;xml>')" />
>>
>> When I validated the XHTML document against the XML Schema, I got this
error:
>>
>> Assertion evaluation ('*[local-name(.) eq
>> 'style']/following-sibling::comment()[1]/starts-with(., '[if gte mso
>> 9]><xml>')') for element 'head' on schema type 'headType' did not succeed.
>>
>> Why does the XPath query work fine when run in Oxygen but fails when
>> used in an XSD 1.1 assert element?  /Roger
>>
>> Here's the XHTML document:
>
>
> --
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