[Koha-zebra] Incomplete CQL Support in Net-Z3950-ZOOM

[Thomas D]

I have found some issues with Net-Z3950-ZOOM for the use of CQL, as the
underlying query syntax for Koha in 3.0 and beyond.  Joshua Ferraro had made
a reasonable case that CQL should be used.  It is certainly easier to
implement semantically meaningful CQL syntax terms than numeric BIB-1
attributes only in the PQF alternative.  Semantically meaningful terms would
certainly make the code more readable and are liable to lead to fewer coding
errors.  CQL usage is already familiar to many as the query syntax in
pre-world wide web catalogues.  Furthermore, the underlying use of CQL in
SRW/SRU, next generation Z39.50 services, would make it a good choice for
the future.  

Mike Taylor. Net-Z3950-ZOOM-1.00 :  ZOOM. - CPAN. 2005.
http://search.cpan.org/~mirk/Net-Z3950-ZOOM-1.00/lib/ZOOM.pod


"scan()"

...

"All of this is done by using a single term from the PQF query as the scan()
argument. (At present, only PQF is supported, although there is no reason in
principle why CQL and other query syntaxes should not be supported in future)."

Scan has many potential very important applications for guiding user queries
based on the contents of the record instead of requiring the user to do more
guessing for what query terms may be actually present in the index for the
database of records.


"sortby()"

...

"It ought to be possible to sort by CQL query, too, but at present
limitations in the underlying ZOOM-C library make this impossible."

Is the lack of sortby() support for CQL merely a significant inconvenience
rather than something that would absolutely prevent the use of CQL when
sorting records by some element is needed?  Can the records otherwise be
sorted by a hierarchy of element in an array using Perl?  Is there an
example of how the result set can be easily accessed by elements in an array
using Perl?

It would be a shame if these issues mitigated against using CQL, the
otherwise best tool for the job.


Thomas D

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