[Bug 29983] [XSLT30] Scanning expressions and function calls

https://www.w3.org/Bugs/Public/show_bug.cgi?id=29983

--- Comment #9 from Michael Kay <mike@saxonica.com> ---
I was asked to produce a revised proposal trying to fix the errors in my
previous version.

So I started thinking: are there any differences between scanning expressions
and motionless patterns, and if so, what are they, and can we justify them?

I came to the conclusion that there are no significant differences.

There are differences of exposition: we say for motionless patterns that for
predicates:  "The expression immediately contained in the predicate is
motionless, when assessed with a context posture of striding, and a context
item type set to the static type of the expression to which the predicate
applies, determined using the rules in 19.1 Determining the Static Type of a
Construct." - while for scanning expressions we simply say that the predicate
must be motionless.

So I propose that we align the concepts, and redefine "scanning expressions" as
follows  (remembering that we are talking here about relative path expressions
only):

A relative path expression is a *scanning expression* if and only if it is the
*equivalent expression* of some *motionless pattern* P.

With that change to the definition, I see little need to change the Note
introduced by comment #3, other than to change the sentence "The subset of
expressions that qualify as scanning expressions is therefore very similar to
the subset that qualify as motionless patterns." - change "very similar to" to
"the same as".

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Received on Thursday, 17 November 2016 22:24:00 UTC