Re: Adam Bosworth Article - what does "directaccess" m ean?
At 11:15 AM 1/16/2003 -0500, W. E. Perry wrote: >Jonathan Robie wrote: > > > In XQuery, you can remain loosely coupled while improving the figure/noise > > ratio of your code. The following computes the PE Ratio for IBM: > > > > let $stock := document("stocks.xml")/stock[@id="IBM"] > > return $stock/price / ($stock/revenues - $stock/expenses) > > > > I do think this is more elegant than the equivalent SAX or DOM. It is no > > more tightly coupled. > >Oh yes it is. This code presupposes 1) a document of a given name; I was trying to write something equivalent to Adam's DOM sample, which does specify the name. However, I agree that there can be real advantages to accessing this through input() so that any document can be accessed in this manner: let $stock := input()/stock[@id="IBM"] return $stock/price / ($stock/revenues - $stock/expenses) >2) a specifically-labelled ("IBM") ID on an element in that document; 3) >specifically-labelled 'price' and 'revenue' information items which are 4) >specifically presupposed to be part of that document (as opposed to say, >separately computable or capable of being looked up in some place of greater >local interest, such as the last trade in a particular market) Walter, either the DOM program or the XQuery program can look up the names before using them, and that does provide more flexibility, but again, I was trying to compare apples to apples, and the DOM fragments that Adam shows do not do this. >and 5) [most crucial of all unexamined assumptions here] presupposed to be >in a form >against which the computation expressed in the code is directly executable >(though, of course as 'real' XML the only form that they would necessarily be >in is Unicode text). No, the XQuery I showed you does not make this assumption. The data might be in an XML document that can be accessed and parsed using the document() function, or it might be in a view of some other resource such as a relational database. Jonathan
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