On Thu, 17 Jul 2003, Matthew J. Dovey wrote:

> Essentially this is reintroducing eSpec into SRW?

Yes.  We need it in Z39.50, and I think we need it here too.

> But will this actually solve the problem sited. If you are sending a DC
> record with no title, odd's are you will still send no title if it was
> eSpec for title (it would just be an evening emptier record).

Not for title, the example was overly simple, but say that you want a
particular field or fields which may or may not get mapped from
whatever schema they're actually in into your simple request schema
(likely DC for a simple display).

But equally, say that they aren't there in a long long DC record.  You
just throw the entire record away after retrieving and parsing it.  At
least if it's not there using XPath you get a simple diagnostic saying
it's not there rather than having to go look for it.

For example, EAD has a multilevel structure.  I might want to say give me
the first component element within the structure.  Or the second. Or I
might want just a field from the first component, like its title or date.
Either I ask for the entire record (and these things get Very Large) or I
make up a schema which I know means 'the first component within the
structure'

Likewise, I might want lines 1-5 of a full text encoded in TEI.  Or ...
include other examples here where you don't want to retrieve the entire
document just to throw 99% of it away.  Even /xhtml/head/title would save
a good deal of irrelevant data being moved around.

I don't really buy the 'XPath is open to abuse' argument ... if so we
should get rid of it from sort.  Just because it's expressed in XPath
doesn't mean you have to do it that way.  You could simply have a big look
up table.  Or you can run it in a protected environment. Or ...


Rob

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