> Date: Wed, 3 Nov 2004 11:01:14 -0600
> From: "Thomas G. Habing" <[log in to unmask]>
> As part of developing a CQL parser [...]
Hi, Thomas, it's good to hear from you. I _was_ going to ask why
you're writing your own CQL parser when there are already free ones in
four different languages; but then I realised you're probably writing
in Visual Basic -- right?
> I have been collecting sample queries. My sample test page is:
> You can click on a sample query to generate the XCQL equivalent.
What a useful page!
> However, there seem to be a few examples floating around, such as:
> title = ((dinosaur and bird) or dinobird)
> that do not seem to be supported by the BNF, either the 1.0 or 1.1
> versions. My questions is are these valid queries, or am I miss
> reading the BNF?
You are not misreading the BNF; on the contrary, the BNF is
miswritten. You are correct that, as currently written, the offical
CQL grammar arbitrarily prohibits such perfectly reasonable and useful
author=(kernighan or ritchie)
There is no good reason for this prohibition (indeed, I am
hard-pressed even to think of a _bad_ reason for it), so three of the
four well-known parsers (my Java one, Adam's C one and Ed Summers's
Perl one) all go right ahead and parse this in the obvious way,
generating the obvious XCQL which cannot possibly be interpreted as
meaning anything other than what it obviously means. And, as you
noticed, my tutorial also goes right ahead and tells people to use
this useful construction.
The correct outcome here is for the CQL grammar to be fixed. I don't
see that happening before v1.2, which is not slated for any time soon,
but when 1.2 comes around I will dedicate 23 hours a day to making
sure this piece of brain damage is excised from the specifications.
In the mean time, a choice confronts you in the development of your
parser: either you can stick to the letter of the what the official
grammar says, and make a less useful piece of software; or you can
make something that your users will not keep emailing you with
Tricky call, huh? :-)
/o ) \/ Mike Taylor <[log in to unmask]> http://www.miketaylor.org.uk
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-- Jane MacDonald.
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