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[XSL-LIST Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: comparing nodesets to each other
 IMO the general problem of finding the differences between any 2 XML documents is, shall we say, challenging. Something that helps such an operation is being extremely precise about what constitutes a difference, and being able to formulate precedence rules in comparision operations. An earlier respondent illustrated the need for this with an example that "added" a node in the second document. It's very likely *you* have a good idea of what you're after, but in these types of problems you'll get the most help if you can express your "rules for comparision" in [formal] written form. Consider the following documents: doc1.xml ======= <doc> <chapter n="1"/> <chapter n="2"/> </doc> doc2.xml ======= <doc> <chapter n="1"/> <chapter n="2"> <para n="1"/> </chapter> </doc> What *exactly* would you like in your final output? Do you want to see only the node <para n="1"/>? Do you want to see <para n="1"/> and all its parent nodes? You see where this is going? It helps to be precise. Also, while writing a "general" differencing algorithm would be worthwhile, it's probably not simple. To start you'll have better luck if you constrain your problem, as it relates to your domain. One way to do this is by identifying a least granular level for your purposes--perhaps a node or "level" below which identifying differences is superfluous. In the example above, you could say: --chapter nodes are compared by their "n" attribute --if there are any differences betweein 2 <chapter> nodes or any of their descendents, the entire <chapter> node is considered "changed", and that of doc2.xml is output I've done this type of "constrained" comparision with success. Here's another approach to consider: preprocess each xml document to a "standard" format, then use a textual diff tool. The idea here is that you apply an XSL transform to doc1.xml so that <chapter> nodes are sequential, their descendents are ordered is a specific way, etc. Do the same with doc2.xml. Then use a diff tool ( eg: beyondcompare, from http://www.scootersoftware.com/ ) to check differences. Note, this method is susceptible to line-breaks, so it's not trivial to implement. Regards --A From: "Kai Hackemesser" <kaha@xxxxxx> Reply-To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx Subject: Re: comparing nodesets to each other Date: Mon, 11 Apr 2005 18:18:47 +0200 (MEST) _________________________________________________________________ Dont just search. Find. Check out the new MSN Search! http://search.msn.click-url.com/go/onm00200636ave/direct/01/ 
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