Re: Dividing documents based on size of contents

Cheers
Chris

I think this is a case for "sibling recursion" - in fact, it's the example I
use on training courses, if I think the group is capable of tackling the
problem (it tends to cause significant headache, and people are typically
amazed how after 3 hours head-scratching, the answer turns out to be about
ten lines of code).

It's probably easiest to do this in two phases: the first phase copies the
documentDivision elements, inserting a <documentBreak/> element where
appropriate, and the second phase uses for-each-group
starting-with="documentBreak" to create the document elements.

The sibling recursion works like this

<xsl:template match="documentDivision">
<xsl:param name="size-so-far" as="xs:integer"/>
<xsl:variable name="new-size-so-far" as="xs:integer"
select="$size-so-far + count(pagebreak)"/>
<xsl:variable name="start-new-document" as="xs:boolean"
select="$new-size-so-far gt 100"/>
<xsl:copy-of select="."/>
<xsl:if test="$start-new-document">
<documentBreak/>
</xsl:if>
<xsl:apply-templates select="following- sibling::documentDivision[1]">
<xsl:with-param name="size-so-far"
select="if ($start-new-document) then 0 else $new-size-so- far"/>
</xsl:with-param>
</xsl:apply-templates>
</xsl:template>


and then you start the process off with

<xsl:template match="document">
  <xsl:apply-templates select="documentDivision[1]"/>
</xsl:template>

Regards,

Michael Kay
http://www.saxonica.com/
http://twitter.com/michaelhkay

-----Original Message-----
From: Chris von See [mailto:chris@xxxxxxxxxxxxx]
Sent: 27 May 2009 02:54
To: xsl-list
Subject:  Dividing documents based on size of contents

Hi all -

I have what I think is a fairly simple problem, but I'm
having trouble with the implementation in XSLT.  Any help you
could give would be greatly appreciated.

I have a document which is subdivided into multiple sections,
with each section, in turn, divided into pages as shown below:

<document>
	<documentDivision>
		... arbitrary content ...
		<pagebreak />
		... arbitrary content ...
		<pagebreak />
	</documentDivision>

... arbitrary number of <documentDivision> elements ...

</document>

Each <documentDivision> section of the document can have an
arbitrary number of <pagebreak> elements, and an arbitrary
amount of content between <pagebreak>s.

I'd like to be able to break the input <document> into
multiple <document>s, each of which has the minimum number of
<documentDivision> sections that give it a <pagebreak> count
~100 pages.  I'd like to break the input at
<documentDivision> boundaries, but I don't need the output
documents to be equally sized or to be exactly 100 pages long
- just as close to that size as I can reasonably get while
maintaining the <documentDivision> boundaries.

So for example if I have an input document that looks like this:

<document>
	<documentDivision>
		... content containing 50 <pagebreak /> elements ...
	</documentDivision>
	<documentDivision>
		... content containing 50 <pagebreak /> elements ...
	</documentDivision>
	<documentDivision>
		... content containing 127 <pagebreak /> elements ...
	</documentDivision>
	<documentDivision>
		... content containing 5 <pagebreak /> elements ...
	</documentDivision>
	<documentDivision>
		... content containing 23 <pagebreak /> elements ...
	</documentDivision>
	<documentDivision>
		... content containing 78 <pagebreak /> elements ...
	</documentDivision>
</document>

the output documents should look like this, with each output
document being "close" to 100 pages in length:

<!-- This doc has enough <documentDivision> elements to give
exactly 100 pages. --> <document>
	<documentDivision>
		... content containing 50 <pagebreak /> elements ...
	</documentDivision>
	<documentDivision>
		... content containing 50 <pagebreak /> elements ...
	</documentDivision>
</document>

<!-- This doc has a single <documentDivision> element with
127 pages - close enough! --> <document>
	<documentDivision>
		... content containing 127 <pagebreak /> elements ...
	</documentDivision>
</document>

<!-- This doc has a three <documentDivision> elements of 5,
23 and 78 pages each - close enough! --> <document>
	<documentDivision>
		... content containing 5 <pagebreak /> elements ...
	</documentDivision>
	<documentDivision>
		... content containing 23 <pagebreak /> elements ...
	</documentDivision>
	<documentDivision>
		... content containing 78 <pagebreak /> elements ...
	</documentDivision>
</document>

I've been able to figure out how to get the number of
<pagebreak>s per <documentDivision> and how to calculate the
number of <pagebreak>s in any given group of
<documentDivision> sections, but what I'm not sure of is how
to maintain information about the point at which I last
created a new output document so that I can determine what
group of <documentDivision> elements has a page count around
100 and should therefore be used to create a new output
document.  It seems that the best way to carry this context
would be via params to xsl;apply- templates, but I'm not
clear on how to set up the XSLT code so that the state gets
maintained as I iterate through <documentDivision> elements.
It also seems like there should be some XPath expression that
I can use with xsl:for-each-group, but I can't quite figure
out how to write that such that each group has only the
minimum number of <documentDivision> elements needed to
accumulate 100-ish pages.

Do you have any guidance on ways to do this?  I think I'm
just having a mental block, and a swift kick in the right
direction should do the trick.

Thanks
Chris

Chris von See
Senior Geek
TechAdapt, Inc.
2910 Heights Dr.
Bellingham, WA  98226

E: chris@xxxxxxxxxxxxx
P: +1 360 223 1514
F: +1 360 544 0112