Re: [xsl] Using for-each w/ page-sequence results in "NC105 ID already exists in this document" error

["G. Ken Holman" <gkholman@xxxxxxxxxxxxxxxxxxxx>]

At 2007-09-19 16:53 -0400, Sharon_Harris@xxxxxxxxxxxxxxxxxxxx wrote:
> I am unable to generate a PDF file using a for-each loop before a page
> sequence if I am using IDs.I am using XSLT 1.0 and Apache FOP.

There is no relationship between XSLT's for-each and XSL-FO's page-sequence.

To diagnose your situation, use XSLT to create an instance of XSL-FO 
and then inspect XSL-FO to determine what the problem is.  That will 
then tell you where you went wrong in your XSLT.

> I have a couple of page sequences defined. In 1 page sequence, I have a TOC
> with IDs that point to elements that are outputted in a 2nd page sequence.

Those should be ref-id= attributes and not id= attributes.  Check 
your XSL-FO instance to make sure <page-number-citation> is using ref-id=.

> The 2nd page sequence is for Lessons and starts with a for-each loop
> calling a Lesson element that will output all the lesson content within the
> body of the Lesson page sequence. However, I encounter the following error:
> "NC105 ID already exists in this document".

This tells me that when you open up the generated XSL-FO file you 
will find id= being used more than once.

> I have unique ID prefixes specified in all Lesson children elements that
> are to be listed in the TOC so I am unsure why the IDs are repeated for
> each instance of the Lesson element.
>
> I have tried creating the Lesson page sequence without using a for-each
> loop and merely using <apply-templates select="//Lesson" mode="activity">

Note that the use of "//" is the most common way of making a very 
inefficient stylesheet.  If you think you need "//", think again 
because you may not need to incur the overhead.

> and this outputs fine except that the page sequence instructions do not
> repeat for every instance of the Lesson element. For example, I specify
> that the 1st page of each lesson should not have a header but only the 1st
> instance of the Lesson element has no header displaying but all other
> Lesson element instances have a header on the 1st page. But I do not run
> into the issue that the IDs are not unique for each instance of a Lesson
> element.

By not including a code fragment from your stylesheet, it is not 
possible to comment on where you might be wrong.

> Am I correct in thinking that in order to get the page sequence to start
> over for each instance of the Lesson element, that I need to have a
> for-each statement before the page sequence?

No, that is not correct.  Any XSLT instruction at all can be used to 
create any XSL-FO instruction at all.  In fact, you don't need XSLT 
(I have a Python program on my web site that uses XSL-FO as a page 
layout language, with no XSLT involved whatsoever).

In fact, a "push-oriented" stylesheet using <xsl:apply-templates/> 
can in many ways be more flexible and maintainable than a 
"pull-oriented" stylesheet using <xsl:for-each>.

> If so, how do I ensure the IDs are unique for every instance of the 
> Lesson element?

By inspecting the XSL-FO instance to determine where your duplicate 
identifiers are being specified using id=, and then finding where in 
your XSLT the result tree with those extraneous identifiers are being 
generated, then changing the XSLT accordingly.

I hope this helps.

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

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