If this is a real requirement I believe the only sensible solution is the
straightforward one (that I think Matthew is suggesting), that is, add
another parameter -- next version of course. Call it something like
'container', with two sub-parameters (1) name/id of a container schema, e.g.
mets; and (2) one or more "base" schema name/ids, e.g. mods, rec, dc. Or,
if we insist that we cannot have structured parameters in the request then a
space separated list of schema names where the first is a container and
those following are base schemas. Or this could be defined as an extension.
But the point is, don't make it any more complicated than that -- in
particular don't overload the existing schema parameter. Hopefully we've
learned that lesson from Z39.50, where ironically it was almost the exact
same problem we were solving more than 10 years ago, widely cited as a
requirement, we spent enormous effort solving it for version 3, and it was
never widely implemented, if at all -- I don't know if the reason was that
the solution was so complicated or if people decided it really wasn't a
requirement after all. But (1) we really did make it more complicated than
it needed to be, and (2) we really didn't adequately scope out the problem.
I think we've learned our lesson about overloading parameters in the name of
compatibility, and the solution to this problem isn't terribly
omplicated -- however I remain skeptical about whether this is a real
problem - real in the sense that if we solve it (in a reasonable fashion)
people will implement the solution.
--Ray
----- Original Message -----
From: "Matthew J. Dovey" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, August 09, 2005 12:30 PM
Subject: Re: rec context set schema
> What's to stop us defining a (potentially infinite) group of
> new schemas, each identified by a URI of the form
> http://loc.gov/sru/mets/<path-to-some-other-schema>
> each of which represents METS records using that nominated schema?
I think the problem here is that a METS record is typically a container
for multiple formats.
So for instance a returned METS record might include the object itself
as an OpenOffice XML doc, the metadata about the object as a MODS XML
doc and the metadata about the record as a rec XML doc (all neatly
wrapped in METS).
So my request would need to be something like
http://loc.gov/sru/mets/path-to-OpenOfficeXMLSchema&path-to-MODS-schema&
path-to-rec-schema - which is workable but messy (and would require a
similar messy mechanism for MPEG21 DIDL and any other wrapper schema)
A neater solution might to be consider how to ask for multiple schemas
within a generic wrapper schema explicitly rather than overloading the
mets/DIDL/etc. schema name - with wildcard support it may even meet
Theo's needs.
Matthew
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