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(_at_)gmail(_dot_)com
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> 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
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