More correctly, you mean Step[Index]/Step[Index]/Step[Index],
but that's fine as that is handled by the definition of AxisStep as it
includes Predicate.
However removing FilterExpr entirely
removes PrimaryExpr and all it brings with it, like literals and function
calls and the use of "." so your change on its own simplifies
things too much. What I think you would need is:
I can see (at least) one problem with only
allowing FilterExpr to appear on its own, namely that you lose the ability
to use "." in conjunction with a path, so even the above is not
sufficient.
Looking at what we have done in the original
spec, all we did was edit the BNF to remove things we didn't support, making
what resulted easily comparable to standard XPath 2.0. The resultant BNF
implies several things that we do not support in DFDL, so we qualified
the BNF with some notes. For example, DFDL only allows the use of Predicates
to index arrays, so there is a note saying that a Predicate must result
in an integer else it's an SDE. I think we should do the same for errata
2.101 - leave the BNF alone and add a new note to the list. And beef
up the words at the start of section 23.4 to make it clear how the BNF
should be read.
Also noticed that the BNF in the spec is
not stand-alone as the constructs for StringLiteral etc are not reproduced,
and rely on the reader reading XPath 2.0 spec.
Regards
Steve Hanson
Architect, Data Format Description Language (DFDL)
Co-Chair, OGF
DFDL Working Group
IBM SWG, Hursley, UK smh@uk.ibm.com
tel:+44-1962-815848
From:
Mike Beckerle <mbeckerle.dfdl@gmail.com>
To:
dfdl-wg@ogf.org,
Date:
05/02/2013 23:08
Subject:
[DFDL-WG] what
do we allow in DFDL expressions after "/"
Sent by:
dfdl-wg-bounces@ogf.org
In reexamining the grammar for the DFDL expression language, I have the
following question
In a path Step/Step/Step[Index]
What can Step be? I know it can be ".." or parent::QName or child::QName
or just an NCName or QName,
Those are all what the XPath grammar calls AxisStep.
anything else?
The grammar can be changed in a very small way from the original
XPath grammar if the above are the only possibilities.
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