RE: RE: Concerned about the increasing reliance on XPath
On Mon, 2011-05-09 at 15:52 -0400, Costello, Roger L. wrote: > Hi Mike, > > > What does your "assessment" step really do anyway? You didn't say. > > There are many ways that one may wish to analyze an XML instance document. For the "purchase XML instance document" we may wish to analyze it to determine: > > - is the value of <Total> a decimal value (and nothing else) > - will the instance document, when evaluated, trigger unexpected and undesirable actions > - is the value of <Total> equal to the sum of its Item siblings > - perform an algebraic data type analysis At this point you're into what I think of as "pipeline validation", where you have a series of steps, typically a sequence, and maybe use XProc to orchestrate it. For example, one step could calculate Total values, another could go to a database and populate product descriptions based on part numbers, another could check the Totals are right :-) and so on... In most cases there's not much point carrying around precomputed values - see Third Normal Form for relational databases for why duplicated information is usually a warning flag. But computing it on the fly, processing the augmented document, and then checking the constraints still hold, that's another matter. I would almost certainly expect to have the logic _outside_ the document in most cases, but e.g. an XML-serialized spreadsheet might not. Liam -- Liam Quin - XML Activity Lead, W3C, http://www.w3.org/People/Quin/ Pictures from old books: http://fromoldbooks.org/
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