RE: [xsl] sequential navigation problem - FOLLOWUP

[Jakob.Fix@xxxxxxxxxxxxxxxxx]

Just to followup on the several ideas proposed for
my sequential navigation issue.

To reduce the processing time (from 3 hours for 15MB
when using the catch-all expressions below), I have
modified my chunker stylesheet in the following way:

- I call a "preprocessing" template that simply scans
  the source document and creates another document
  (prevnext_index.xml) containing a nodeset of all
  nodes I am interested in, *in*document*order*.
  This gives me the following document:

  <bv:nodes>
    <bv:node ID="ACTR.00.B36A178001BE2A74" GI="PART">Part A -
Classification and Surveys</bv:node>
    <bv:node ID="ACTR.01.2B02E5C001BE13AE" GI="CHAP">Chapter 1 - Principles
of classification and class notations</bv:node>
    <bv:node ID="ACTM.03.9FCE36C001BDFCD4" GI="SECT">Section 1 - General
Principles of Classification</bv:node>
    [ ... and another 1800 lines or so ... ]
  </bv:nodes>

- Later on, in the main part of the stylesheet, when
  chunking a fragment, I retrieve the previous and next
  information recorded in the index file using this bit:

    ...

    <xsl:variable name='index.document'
      select='document(concat("file:/", $base.dir, "/",
$index.file.name))'/>

    <xsl:param name="previous.fragment"
      select="$index.document/bv:nodes/bv:node[@ID = current
()/@ID]/preceding-sibling::bv:node[1]"/>
    <xsl:param name="next.fragment"
      select="$index.document/bv:nodes/bv:node[@ID = current
()/@ID]/following-sibling::bv:node[1]"/>

    ...

- This cuts processing time to only 25 minutes, plus 1
  and a half minutes for creating the index document.
  Not too bad for my needs.  But is it "elegant" ;-)?

Thanks to everybody for your help!

Cheers,
Jakob.








"Michael Kay" <michael.h.kay@xxxxxxxxxxxx>@lists.mulberrytech.com on
12/06/2002 10:39:55 AM

Veuillez répondre à xsl-list@xxxxxxxxxxxxxxxxxxxxxx

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Pour :    <xsl-list@xxxxxxxxxxxxxxxxxxxxxx>
cc :
Objet :   RE: [xsl] sequential navigation problem (long)

Ref. Message:

> Jeni, David,
>
> Thanks for your responses.  Thanks for pointing out the error
> in my logic.
>
> I am currently using the catch-all expressions, which works ok,
>
>   (ancestor::* | preceding::*)
>     [self::PART or self::CHAP or self::SECT or self::ART or
>      self::SYMBOLS or self::APPENDIX or self::SART][@ID][last()] and
>   (descendant::* | following::*)
>     [self::PART or self::CHAP or self::SECT or self::ART or
>      self::SYMBOLS or self::APPENDIX or self::SART][@ID][1]
>
Most decent XSLT processors are likely to optimize the [1] predicate by
stopping the search when the first node has been found; but optimizing
[last()] is much more difficult.

My first thought was to rewrite this as:

(ancestor::*[self::part.....][@ID][1]
   or
 preceding::*[self::part....][@ID][1])
  and
(descendant::*[.....][@ID][1]
  or
 following::*[.....][@ID][1])

and see if this speeds it up.

But on reflection, the [1] and [last()] predicates are redundant in a
boolean context: if there are any nodes selected, there will be a first
node and a last node. So it might be enough simply to get rid of the [1]
and [last()] predicates in your expression.

Rearranging the two branches of the "or" might also help: the biggest
cost will come when the first branch does a long search and finds
nothing. The above is probably best, but I don't know your data.

Now I'll go away and tweak the Saxon optimizer so it gets rid of a
trailing [last()] predicate on a path expression used in a boolean
context...

Michael Kay
Software AG
home: Michael.H.Kay@xxxxxxxxxxxx
work: Michael.Kay@xxxxxxxxxxxxxx




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