[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: XPath 1.5? (was RE: typing and markup)
Jonathan Robie wrote: > I think that optimization of // is a more compelling way to use knowledge > of complex types. Suppose you have a pattern like this: > > //address > > Without knowledge of the complex types involved, this requires examination > of all elements in the document to see if they are "address" elements. > Looking at the schema for a particular invoice document, it is easy to see > that the above pattern can only match shipping or billing addresses found > in customers. The optimizer can rewrite the above pattern as follows: > > /customer/billing/address | /customer/shipping/address > This might be expressed using a general constraint system (but using an xpath to name a class) as: intersectionOf(//address , schema) = unionOf( /customer/billing/address, /customer/shipping/address) The effect is that a (static) analysis using such straightforward logical devices results in the "rewriting" of a query/transform, making it _easier_ for the XSLT programmer, who can then feel free to use "//address" without worrying about speed, etc. just like why we have compilers _and_ interpreters, rather than programming in machine language. Jonathan
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