> Date: Thu, 24 Nov 2005 14:03:02 +0000
> From: Rob Sanderson <[log in to unmask]>
> 
>>> What is the benefit of having a marc context set, rather than a
>>> profile which maps marc fields to semantically named and defined
>>> indexes?
>>> 
>>> eg 245 -> dc.title
>>> 999 -> yourPrivateContextSet.yourPrivateField
>> 
>> Surely it's obvious.  If you already have a MARC database which you
>> search in other ways, and want to add an SRU interface to it, then the
>> obvious way to do that is by using a set of indexes that let you
>> trivially translate all the searches you're used to doing.  There
>> really is nothing to be gained in defined private context sets with
>> pricate indexes for such a database.
> 
> If all you are doing is searching your own database, why do you need
> SRU/CQL at all?

So that other people can search it too, of course.  It's not at all
hard to imagine a metasearcher of library catalogues that uses the SRU
MARC profile.

And more generally, it's stupid for us to tell people "You don't want
to use SRU for <x>".  If they want to use SRU, we should give them the
tools they need to do so.

> If you want others to search your database, then how will they know
> what your 999 field means?  Equally, how will they know if your
> database is UKMARC, USMARC, FINMARC etc with all of their cute
> little variations? How are they going to know that you've put notes
> in 521a and 520d, but not 500a?

Pish tish.  These are merely problems to be solved, not reasons to
declare the whole enterprise pointless.  The bottom line is that we
can't predict what people will want to use this for, so we shouldn't
try to prescribe.  "Mechanism, not policy".

> Or you could send 'xxx.noteText any foo' and do the right thing of
> leaving it up to the database to interpret that index against its
> own data.

Yes.  SRU/MARC servers can indeed also support this.

> How do I know that any given SRU interface is to a MARC database?

Explain?  Out-of-band agreement?

> I think I'm searching a "GENERAL NOTE" field with 500a, but actually
> it's "SEE ALSO FROM TRACING--PERSONAL NAME" (whatever that means :))
> And if so, how does a machine know if it's searching a bibliographic
> database or an authority database?

Don't Do That, Then.  This is a problem of resource discovery.

> Also, SRU doesn't allow for the concept of a MARC database any more
> than it allows for the concept of an XML database, a PDF database, a
> JPG database or any other format.

Sure it does.  SRU doesn't say anything one way or the other on the
subject, and nor it should.

> In short, if there's nothing to be gained by using semantically
> aligned searches, what's the gain of using CQL and/or SRW/U at all?

As we all agree, there is a very great deal to be gained by using
semantically aligned searches.  But just because this is a
particularly excellent solution, we shouldn't try to impose on every
problem.

 _/|_	 ___________________________________________________________________
/o ) \/  Mike Taylor  <[log in to unmask]>  http://www.miketaylor.org.uk
)_v__/\  "Bonjour, Betty-Muriel, c'est nous!" -- Monty Python's Flying
	 Circus.