RE: [xsl] Calculating cumulative values - Abel's solution

[Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>]

At 02:14 PM 8/31/2007, you wrote:
> One day I'll understand the lingo!  What I meant was that I was hoping the
> output would be identical to the input except for the addition of the new
> cumulative attributes y2 and y3.  Is this called an "identity
> transformation"?

Simon,

An identity transformation is one in which the output is identical to 
the input, with allowances made for changes that aren't supposed to 
count, such as the order of attributes. In other words, "tag 
fidelity" is not required, but as far as the XML document-as-tree is 
concerned, you get out just what you put in.

While pure identity transforms are sometimes useful (for example, you 
may want to transcode character sets), it is much more common to want 
your output to be nearly identical, not perfectly identical, to your 
input, and indeed such transformations are very common in XSLT. This 
describes your case exactly.

These transformations commonly use the "identity template" -- which 
is one or another variant of a template that copies a node into the 
output, and then applies templates to its children (those who haven't 
memorized it can find it easily on the web) -- plus one or two other 
templates to introduce just the changes wanted. For this reason, 
these transforms are often called "identity transforms" although 
strictly speaking, they might be better described as "near-identity 
transforms" or "modified copying transforms".

Cheers,
Wendell



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Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
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