Mike Taylor wrote:
>>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,
>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:
>(It would be interesting to know the date of the first edition,
Yep.. and the ISO standard is based on other standards that go further
back... I've heard rumors that it was originally a Danish specification,
which would be particularly ironic since one of the fathers of Algol and
BNF (Peter Naur) was a Dane.. still legendary around the institute of
Computer Science in Copenhagen for his draconian approach to grading papers.
>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
>(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" :-)
We do enjoy the occasional, carefully chosen understatement.
>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.
AFAIK, one of the crucial differences (unless this was changed in CQL?)
is that the CCL spec doesn't require quotes around multi-word terms...
this makes the grammar and parsing of CCL queries somewhat more challenging.
Sebastian Hammer, Index Data (US)
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