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Re: requesting XML records

From: Jonathan Rowell <bigrat18@hotmail.com>
Date: Wed, 26 Mar 2003 13:40:42 +0100
To: rden@loc.gov
Cc: www-zig@w3.org
Message-ID: <F66m2CaO9smko29fWhw000222d9@hotmail.com>

Hi all!

If I may, as an outsider, be allowed to put in my penny's worth on this 
subject, since it interests me greatly.

Ray wrote first:

"That's my attempt to summarize the issue. My
proposal is to adopt the approach used by SRW when
faced with a similar problem. For the esn, use a
URI that serves as an identifier for the desired
schema (you don't have to call it a namespace)."

and later to Diana Dietz :

"if you try to go to:
http://www.loc.gov/zing/srw/dcschema/v1.0/  you'll get "Not Found" because 
it's
not intended as an actionable uri but as an identifier, the same way that an 
oid
is an identifier. We *can* guarantee persistence of this uri, as well as
un-ambiguity.  If a new version is developed, there will be a new uri, maybe
http://www.loc.gov/zing/srw/dcschema/v1.1/, but the old uri
(http://www.loc.gov/zing/srw/dcschema/v1.0/) will continue to identify 
version
1.0."

Now for me that's a namespace. If you want to validate a document using a 
DTD or
a schema, you'd cache the thing locally (to avoid fetching it over the net) 
and
match an identifier in order to use it. This is the namespace. Everybody 
does it,
XSL, XSD, Marc21.

The use of XML defines a language. This becomes fixed like the oids. But 
it's worse
than that, the structure of the contents becomes fixed. Before one could 
cheat a
bit by returning "something like". But not anymore. You have to ask the 
server to
return the data in that XML language and either it does or it can't. That's 
it.


Theo van Veen wrote :

"The real problem is that XML schemas are not sufficient to express what you 
what
to express. We had a similar discussion also at the ZNG list. There should 
be a
way (a generic more schema) to request DC records without caring about the 
small
differences in different versions."

Exactly! We have this today. What do you think I'll get if I ask a Norwegian 
server
for a German MAB record? (What do think I'll get if I ask a German server 
for the same!)
As an implementor I'd bang over the identifier for the format, get the XML 
back, validate it syntatically, look at the namespace provided, look up in a 
table of namespaces for an
XSL transform and transform the XML data into the required format and throw 
it at the user (poor swine).

Ray wrote :

"One suggestion is to assign object identifiers
subordinate to 1.2.840.10003.5.109.10.  This idea
has a number of disadvantages and unless someone
wants to pursue this approach I'd prefer to
discard it."

Seems to me the only way to stop a greater proliferation than you currently
have is to allocate oids for all XML formats. The oid authority should 
insist
that, in order to get an oid registered, there must be an authority which
maintains a namespace and a DTD or schema to go with it. The latter the
implementors may cache. The problem is the update. You ask for a particular
format and get a different one. This in fact is no worse than today. The oid
for German MAB actually gives you MAB2. Is this not the case for DANMARC and 
the
rest of Scandanavia? You always get the new format. If however the namespace 
is
mandatory in the data returned, we have a chance of sorting it out using 
very
powerful tools like XSL.

Jonathan


>From: Ray Denenberg <rden@loc.gov>
>To: zig <www-zig@w3.org>
>CC: Lunau Carrol <carrol.lunau@NLC-BNC.CA>, slavko@mun.ca
>Subject: requesting XML records
>Date: Tue, 25 Mar 2003 14:38:12 -0500
>
>
>We need an agreement among Z39.50 implementors on
>how to request xml records.  This is, in
>particular, an urgent issue for Bath profile
>implementors.
>.........................
>
>--Ray
>


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Received on Wednesday, 26 March 2003 07:40:49 GMT

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