Subject: RE: [xsl] Incremental Update: change a portion of the XML and the XSLT operates on just that portion From: "Michael Kay" <mike@xxxxxxxxxxxx> Date: Wed, 20 Jan 2010 20:06:30 -0000 |
I think incremental transformation was one of the motivations for making XSLT a declarative, function language. There has been research work to try and make this a reality, sufficient to prove that it can be done: see for example http://www.research.ibm.com/people/v/villard/Papiers/incxslt/incXSLT.html but it has not found its way into mainstream products. One reason, I think, is that experience has shown that with modern hardware, "rendering" stylesheets are usually extremely fast on the kind of documents that are viewed interactively, and re-rendering the entire document is a feasible proposition, meaning there is not much incentive to make it faster. Regards, Michael Kay http://www.saxonica.com/ http://twitter.com/michaelhkay > -----Original Message----- > From: Costello, Roger L. [mailto:costello@xxxxxxxxx] > Sent: 20 January 2010 16:25 > To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx > Subject: [xsl] Incremental Update: change a portion of the > XML and the XSLT operates on just that portion > > Hi Folks, > > 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 what's 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? > > /Roger
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