Kris,
this sounds very
familiar to me. Once I had to make a reporting module with PDF generation. When
I looked at the existing reports (about 50-60 of them), I found out that they
are all (surprise!) similar :)
Actually, now I
think that I found an example of self-similar fractals in reporting domain,
maybe I can claim for Turing award :)
Seriously,
after few hours of thinking I came to
conclusion that they all can be constructed with a limited number of elements,
which can be nested and combined. I called them "layoutlets".
By nesting and joining 3-4 layoutlets, one can generate unlimited
variety of report layouts.
As far as I
remember, I identified three main structural layoutlets for my reports:
list, vertical-list and table. I also had some other stuff, like row,
column, multi-line row etc.
So, when I
extracted data from DB, I put it into content XML. Something
like:
<resultset
name="master">
<row><col id="1">Wow</col>
<resultset
name="nested"><row><col
id="1">Meow</col></row></resultset>
</row></resultset>
This has a nested
resultset. Next step was to write stylesheet which makes as you call it
"structural" XML, I called it layout sheet. This would use my layoutlets, which
are defined as templates in a separate stylesheet library (I called it generic).
Example:
<xsl:template match
="row[../@name='master']"
mode="list">
<xsl:call-template
name="row-list">
<xsl:with-param
name="columns"><xsl:call-template
name="list-columns"/></xsl:with-param>
<xsl:with-param
name="is-nested" select="true()"/>
</xsl:call-template>
</xsl:template>
The above
template uses "row-list" layoutlet to render the "master" resultset. "row-list"
template is defined in generic layoutlet library. I can cimply change this
layoutlet, and all reports will be affected. "row-list" renders coumns of the
row as a vertical list using XSL-FO. At the end I get XSL-FO file and make
PDF out of it using FOP or something else.
So, the report
specifi stylesheet only has to map resultsets in content XML to appropriate
layoutlets (generic templates). What's interesting is that layoutlets are
orthogonal, so I can combine them in any order. Orthogonality also is very good
for stylesheet languages, as you know, because it makes template writing very
straightforward.
cheers,
Argyn
Let me know what you guys think about this.
The general idea these days is to seperate content logic and style, as
cocoon does very well. However, I think it is even better if you can seperate
structure from style. The way i have done this in the past is with template
calling in xsl. However, I think it would be much cleaner to have two style
sheet transformations in cocoon, one that takes content to structure, and
another that takes structure to style.
For example, if I had an employee database that output xml like this
(content):
<employee id=2>
<name>Some
Name</name>
<phone>343234234</phone>
...
</employee>
I would then transform it to some structural language like this:
<box title="[EMAIL PROTECTED]">
<section
title="details">
....
</section>
<section
title="some other section">
</section>
</box>
And then finally transform the structural elements to some sort of
presentational form.
Preferably the structural language would consist of as few as possible
elements, maybe a couple types of box's, a couple types of lists, a couple
types of sections, etc.
Do people do stuff like this already, and if so are there any good xml
languages that one could use to describe structure?
Kris
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