Re: [xsl] Incremental Update: change a portion of the XML and the XSLT operates on just that portion

Subject: Re: [xsl] Incremental Update: change a portion of the XML and the XSLT operates on just that portion
From: "James A. Robinson" <jim.robinson@xxxxxxxxxxxx>
Date: Wed, 20 Jan 2010 08:35:17 -0800
My impression is that this bit you quote is theoretical right now,
that there aren't any XSLT engines that can perform that kind of analysis.

So performing that kind of work would end up having to be programmed at
the application level instead of being something the engine could just
figure out.


> On page 987 of the book, "XSLT 2.0 and XPath 2.0" the author Michael Kay discusses the advantages of functional programming. One of the main benefits, he argues, is the ability to do incremental updates. Here is a paragraph that really captured my interest:
> 
> ------------------------------------------------------
> We want to get away from static pages; if you're showing a map of traffic congestion hotspots in your area, then when the data for a particular road junction changes, you want the map updated in real time, and it should be possible to do this without recalculating and redrawing the whole map. This is possible if there's a direct relationship--a function--between whats shown at a particular place on the map display and a particular data item in the underlying database. So if a program is decomposed into a set of smaller, independent functions, each relating one piece of the output to one piece of the input, then we have the potential to do this on-the-fly updating.
> ------------------------------------------------------
> 
> Wow!  I want to do that.  But how?
> 
> Suppose that I have an XML document and an XSLT transform. The XSLT transform processes the entire document and outputs, say, an HTML document. Later, I update one portion of of the XML document. How do I get the XSLT to operate on just the updated portion? And how does the XSLT update just the relevant portion of the HTML document?

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James A. Robinson                       jim.robinson@xxxxxxxxxxxx
Stanford University HighWire Press      http://highwire.stanford.edu/
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