Syd: Simpler XPath to select @xml:id attrs; bug fix: double-escape '<'

2015-10-15T02:43:55Z

Simpler XPath to select @xml:id attrs; bug fix: double-escape '<'

Syd: added page

2015-10-02T22:56:28Z

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It is often convenient to validate XML documents against RELAX NG schemas ''without'' using the “DTD Compatability” feature of RELAX NG. (Particularly when
using certain wildcard patterns, as this feature can cause a “conflicting ID-types for attribute "id" from namespace "http://www.w3.org/XML/1998/namespace" of element …” error. Personally, I think getting notified of the conflict is good, but it should be a warning, not an error.) However, when DTD Compatability is turned off, the RELAX NG validator no longer tests that the values of your ID attributes (which, in TEI, means your <tt>@xml:id</tt> attributes) are unique across all IDs in your document.

Here are three slightly different ways to test for unique <tt>@xml:id</tt> attributes in ISO Schematron.

BTW, in oXygen this feature can be turned on and off in <tt>Options > Preferences… > XML > XML Parser > RELAX NG</tt> pane by checking or unchecking the <tt>Check ID/IDREF</tt> box. The easy way to get to it is to filter for the string “IDREF”, which does not appear in any other preference panes. At least this works in oXygen 17.

<pre><nowiki><?xml version="1.0" encoding="UTF-8"?>
<sch:schema xmlns:sch="http://purl.oclc.org/dsdl/schematron" queryBinding="xslt2"
xmlns:sqf="http://www.schematron-quickfix.com/validator/process">

<sch:p>This Schematron schema contains three different ways of doing
exactly the same thing: checking that each and every @xml:id
attribute in the input has a unique value.</sch:p>
<sch:p>I do not know which of these three methods, or some other, is
“best”, and I’m not sure there is any way to know. While #2 has the
shortest XPath, I think #3 is easier to understand. But if you think
#1 or #2 is easier to understand, by all means use it.</sch:p>
<sch:p>Note that none of these rules check that the value of @xml:id
is a valid identifier, or even that it is present. They only check
for uniqueness.</sch:p>
<sch:p>Written 2015-10-02 by Syd Bauman. Copyleft.</sch:p>

<sch:pattern>
<sch:rule context="//@xml:id">
<sch:let name="myID" value="normalize-space(.)"/>
<sch:report test=" ../ancestor::*/@xml:id[ normalize-space(.) eq $myID ]
|
../preceding::*/@xml:id[ normalize-space(.) eq $myID ]
">#1 The @xml:id "<sch:value-of select="."
/>" on <<sch:value-of select="name(..)"
/>> duplicates an @xml:id found earlier in the document</sch:report>
</sch:rule>
</sch:pattern>

<sch:pattern>
<sch:rule context="//@xml:id">
<sch:let name="myID" value="normalize-space(.)"/>
<sch:report test="//*[ current()/.. >> .]/@xml:id[ normalize-space(.) eq $myID ]
">#2 The @xml:id "<sch:value-of select="."
/>" on <<sch:value-of select="name(..)"
/>> duplicates an @xml:id found earlier in the document</sch:report>
</sch:rule>
</sch:pattern>

<sch:pattern>
<sch:rule context="//@xml:id">
<sch:let name="myID" value="normalize-space(.)"/>
<sch:report test="../(ancestor::*|preceding::*)/@xml:id[ normalize-space(.) eq $myID ]
">#3 The @xml:id "<sch:value-of select="."
/>" on <<sch:value-of select="name(..)"
/>> duplicates an @xml:id found earlier in the document</sch:report>
</sch:rule>
</sch:pattern>

</sch:schema>
</nowiki></pre>

[[Category:Schematron]]

@@ Line 23: / Line 23: @@
    <sch:pattern>
-     <sch:rule context="//@xml:id">
+     <sch:rule context="@xml:id">
        <sch:let name="myID" value="normalize-space(.)"/>
        <sch:report test=" ../ancestor::*/@xml:id[ normalize-space(.) eq $myID ]
@@ Line 29: / Line 29: @@
                           ../preceding::*/@xml:id[ normalize-space(.) eq $myID ]
                          ">#1 The @xml:id "<sch:value-of select="."
-                         />" on &lt;<sch:value-of select="name(..)"
+                         />" on &amp;lt;<sch:value-of select="name(..)"
                          />> duplicates an @xml:id found earlier in the document</sch:report>
      </sch:rule>
@@ Line 35: / Line 35: @@
    <sch:pattern>
-     <sch:rule context="//@xml:id">
+     <sch:rule context="@xml:id">
        <sch:let name="myID" value="normalize-space(.)"/>
        <sch:report test="//*[ current()/.. >> .]/@xml:id[ normalize-space(.) eq $myID ]
                          ">#2 The  @xml:id "<sch:value-of select="."
-                         />" on &lt;<sch:value-of select="name(..)"
+                         />" on &amp;lt;<sch:value-of select="name(..)"
                          />> duplicates an @xml:id found earlier in the document</sch:report>
      </sch:rule>
@@ Line 45: / Line 45: @@
    <sch:pattern>
-     <sch:rule context="//@xml:id">
+     <sch:rule context="@xml:id">
        <sch:let name="myID" value="normalize-space(.)"/>
        <sch:report test="../(ancestor::*|preceding::*)/@xml:id[ normalize-space(.) eq $myID ]
                          ">#3 The @xml:id "<sch:value-of select="."
-                         />" on &lt;<sch:value-of select="name(..)"
+                         />" on &amp;lt;<sch:value-of select="name(..)"
                          />> duplicates an @xml:id found earlier in the document</sch:report>
      </sch:rule>

Xmlid uniqueness.sch - Revision history

Syd: Simpler XPath to select @xml:id attrs; bug fix: double-escape '<'

Syd: added page