Subject: Re: [xsl] Simple Map Expression Grammar definition in the XPath 3.0 Recommendation From: "Michael Kay mike@xxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> Date: Sat, 10 May 2014 19:44:32 -0000 |
This continues a long tradition of the way the XPath grammar is defined. For example, in XPath 1.0, we have AdditiveExpr ::= MultiplicativeExpr | AdditiveExpr '+' MultiplicativeExpr | AdditiveExpr '-' MultiplicativeExpr meaning that an AdditiveExpr does not necessarily contain a +/- operator, and leading to messy phrases like: "An EqualityExpr (that is not just a RelationalExpr) or a RelationalExpr (that is not just an AdditiveExpr) is evaluated ..." In my book I chose to refer to an AdditiveExpr than actually contains a +/- operator as a "non-trivial AdditiveExpr" In the XSLT 3.0 spec we have also had to address this problem when classifying expressions for streamability: " expressions are classified according to the most specific production rule that they match....", so 3*2 is classified as a MultiplicativeExpr even though it is also a (trivial) instance of AdditiveExpr. Perhaps there is a better way of doing it, but it's certainly not an error. Michael Kay Saxonica On 10 May 2014, at 19:29, Dimitre Novatchev dnovatchev@xxxxxxxxx <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote: > The W3C XPath 3.0 Recommendation XPath 3.0 grammar defines Simple Map > expression in this way > (http://www.w3.org/TR/2014/REC-xpath-30-20140408/#id-map-operator): > > [34] SimpleMapExpr ::= PathExpr ("!" PathExpr)* > > It follows from this rule that a SimpleMapExpr is, among other things, > any PathExpr -- because "*" means "zero or more". > > It seems rather weird to call an expression that doesn't contain any > instance of the simple map operator, a "simple mapping expression". > > My guess is that the rule was meant as: > > [34] SimpleMapExpr ::= PathExpr ("!" PathExpr)+ > > According to this rule, a SimpleMapExpr should contain at least one > instance of the simple map operator. > > Hope that this problem is acknowledged and the correction is included > in the Errata. > > -- > 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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