> Date: Mon, 14 Nov 2005 11:21:34 -0500
> From: "Ray Denenberg, Library of Congress" <[log in to unmask]>
> 
>> I still wonder how people can call something a standard that is not
>> publically available. CCL is very poorly documented -
> 
> LC and the SRU Editorial board will soon unveil what we think is
> dramatically improved documentation.

Ray, that particular criticism was of the CCL (ISO 8777)
documentation, not CQL!  (But I can see how you'd be getting used to
having the SRU/CQL pages criticised :-/ )

> Date: Mon, 14 Nov 2005 11:30:53 -0500
> From: Sebastian Hammer <[log in to unmask]>
>
>>> There isn't a mapping between CCL and CQL, but if you'd like to write
>>> one up, then I'm sure that it would be appreciated by many :)
>>
>> CCL is very poorly documented - you can use it in many OPACs in
>> some way but libraries seem to hide it from the user. If you send
>> me a PDF of ISO 8777 I can try to summarize the differences and
>> commonalities with CQL.
> 
> Unfortuantely, ISO8777 doesn't even describe the language that lucidly 
> -- the stnadard predates context-free grammars (at least I hope it does 
> -- otherwise, I don't know what their excuse would be).

I think that excuse is pretty unlikely to stick.  According to the
Wikipedia article on BNF,
	http://en.wikipedia.org/wiki/Backus-Naur_form
it was invented as part of creating the rules for Algol 60.  So
presumably it goes back to the 1950s.  Whereas the most recent version
of ISO 8777 is dated 1993, according to the ISO store:
	http://www.iso.org/iso/en/CatalogueDetailPage.CatalogueDetail?CSNUMBER=16192
(It would be interesting to know the date of the first edition,
though.)

> Adam put quite a bit of effort into capturing the essence of the
> language in a BNF notation.. that might actually be the easiest
> place to start. You'll find it at
> http://www.indexdata.dk/yaz/doc/tools.tkl#CCL

(The opening sentence of this section is my favourite in the whole of
the YAZ manual, and a classic example of phlegmatic Danish
understatement: "Not all users enjoy typing in prefix query structures
and numerical attribute values" :-)

But to summarise the relationship between CCL and CQL: the intention
when CQL was being design (initially by Ralph, and subsequently by the
SRW editorial board as a whole) was that it should be pretty much a
superset of CCL, and that it therefore sets out to provide
_additional_ syntax rather than _alternative_ syntax.  So what you
would hope to find is that most CCL queries are also CQL queries with
the same interpretation, but that you go on to say much more in CQL.

... whether that goal was fully realised is open to debate.

 _/|_	 ___________________________________________________________________
/o ) \/  Mike Taylor  <[log in to unmask]>  http://www.miketaylor.org.uk
)_v__/\  "The idea behind PhyloCode is to get all the bickering done
	 now so the future generations don't have to worry about it" --
	 T. Michael Keesey