Subject: Re: [xsl] Seemingly incorrect example of function subtyping in XDM 3.0 From: Michael Kay <mike@xxxxxxxxxxxx> Date: Wed, 26 Feb 2014 09:02:07 +0000 |
I believe the example is correct. I find it useful to think of "substitutability" rather than subtyping. If the requirement is for a function that accepts a string as an argument, then it's OK to supply a function that accepts any item as an argument. So function(item()) is substitutable for function(xs:string). Michael Kay Saxonica On 26 Feb 2014, at 05:45, Dimitre Novatchev <dnovatchev@xxxxxxxxx> wrote: > In the W3C XDM 3.0 Proposed recommendation at the end of section: > "2.8.1 Functions" (http://www.w3.org/TR/xpath-datamodel-30/#function-items) > > the last example says: > > "function(item()) as item() is a subtype of function(xs:string) as item()" > > I believe that the correct statement is: > > > "function(xs:string) as item() is a subtype of > function(item()) as item() " > > Could someone, please, confirm whether the example in the XDM 3.0 Spec > is correct, and if yes, then what is the chain of rules that leads to > this statement? > > > -- > Cheers, > Dimitre Novatchev > --------------------------------------- > Truly great madness cannot be achieved without significant intelligence. > --------------------------------------- > To invent, you need a good imagination and a pile of junk > ------------------------------------- > Never fight an inanimate object > ------------------------------------- > To avoid situations in which you might make mistakes may be the > biggest mistake of all > ------------------------------------ > Quality means doing it right when no one is looking. > ------------------------------------- > You've achieved success in your field when you don't know whether what > you're doing is work or play > ------------------------------------- > To achieve the impossible dream, try going to sleep. > ------------------------------------- > Facts do not cease to exist because they are ignored. > ------------------------------------- > Typing monkeys will write all Shakespeare's works in 200yrs.Will they > write all patents, too? :) > ------------------------------------- > I finally figured out the only reason to be alive is to enjoy it.
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