Re: XML and XPATH: How do they work?
Hi, On 6/29/05, Joe Schaffner <schaffner.joe@g...> wrote: > XPath looks like some kind of expression language for naming objects, as in > "pathname", not a "link". (I'm guessing that XML objects, being > hierarchical, need some kind of name syntax, like a "pathname".) Not sure what an XML object might be, but xPath is simply a query language for traversing node-trees, and a very good one as such. > The 'link' abstraction in XML is a bit more complicated than I expected, so > I'll need more time to read the documentation. Of course, that depends on just how you model and want to implement your data. > My names <prev> and <next> come from linked list programming in C. They are > unidirectional, so you need one for both directions. They serve as > navigation. Navigation should not be part of your datamodel nor dataset, but be a separate implementation detail. Here's how I'd do your XML stuff; <term id="some.id.x"> <label lang="en">Fiddle</label> <label lang="no">Fele</label> </term> <term id="some.id.y"> <label lang="en">Chin</label> <label lang="no">Hake</label> </term> And when you need a relationship between the two; <relationship of.type="played.on"> <member refid="some.id.x" role="instrument" /> <member refid="some.id.y" role="method" /> </relationship> Then it makes sense to just create a set of words that describe your relationships (of.type and role attributes) (also known as an ontology). This can now all come together in a user interface without any hardwireing. You may want to look at canonical XML for a better understanding of id and refid attributes and somesuch. xLink is when you need (well, mostly) cross-document linking, and *especially* cross-domain cross-linking. Basically my advice would be to keep it simple unless you really have to. > But they are also logical, maintaining either alphabetical order, or the > arbitrary order chosen for the models... These should be part of the interface logic of your application, not be an integral part of datamodel nor dataset. > It looks like there is more than one way to skin a cat. There are often too many, which makes the simple solution hidden. "When facing the sunshine, you won't see the shadows" :) Alexander -- "Ultimately, all things are known because you want to believe you know." - Frank Herbert __ http://shelter.nu/ __________________________________________________
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