Re: DOCBOOK-APPS: DocBook XML / XSL Problems (attribute tests seemalways true)

[Bob Stayton <bobs@caldera.com>]

> From: Benjamin Peter <benjamin@tolkbib.de>
> 
> Hello,
> 
> I have spent several hourse on the problem I posted before and have 
> found out that:
> 
> I am not getting chapter, section, figure numbers because the test
> for @label will be true even if I have no label attribute in the tag.
> 
> Example:
> 
> a) the xml fragment:
> <figure><title>My Sample Figure</title>
> <graphic fileref="sample.jpg"/>
> </figure>
> 
> b) the matching template that will generate the label (fragment)
> 
> I have modified this to tell me whether a @label was found which
> will override the automatically generated id.
> 
> Running it against above xml file (saxon 6.4.2, docbook xml 4.1.2)
> will output 'Label found:'
> 
>    <xsl:choose>
>      <xsl:when test="@label">
>      <xsl:message>
>          Label found:
>          <xsl:value-of select="@label"/></xsl:message>
>        <xsl:value-of select="@label"/>
>      </xsl:when>
>      <xsl:otherwise>
> 	 <!-- Generate the label automatically -->
>      </xsl:otherwise>
>    </xsl:choose>
> 
> c) working template:
> 
> When I modify the line that tests for @label to read
> 
>      <xsl:when test="@label and not(string-length(@label)=0)">
> 
> everything works fine.
> 
> 
> The same problem occurs in several other cases (e.g. an existing but
> empty @scale in graphic will render as an image with a width of "%" in
> HTML :-(
> 
> I understand that the modification of the templates is merely a way to 
> pinpoint my problem, not the solution. I have however no idea what the 
> solution might look like.
> 
> If anyone else has this problem and a solution along with it, please 
> drop me a line.

Perhaps upgrade to Saxon 6.4.4.  I just tried it and I get
figure numbers ok.  If a missing 'label' attribute
generates a true value for test="@label" as your test
demonstrates, then that has to be a bug in the XSL
processor.  An empty node or empty string is false (quoting
Michael Kay's XSLT Programmer's Reference 2nd ed. page
453).

bobs
Bob Stayton                                 400 Encinal Street
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                                            email: bobs@caldera.com