Hi Rob,

> This is just a rehash of a previous discussion on this list, between
> us:
> http://www.mail-archive.com/code4lib@listserv.nd.edu/msg05309.html
> So I guess I'm wasting my time ;)

Thanks, I added a link to the previous discussion. You wrote:

Referring to your blog post, you can say how the four inter-relate:

Schema Identifier uniquely identifies the format.
Schema Location is a non-unique description of the format.
Schema Name is a short, human readable, non-unique name for the format
and Namespace is a non-unique namespace used by the format.

These definitions can help to clarify things, but they are of little practical value. The practical question is how to refer to a particular format. If you have to manually look at each particular server and collection to find out what format is *actually* served, then names and identifiers are of little help to code against. Both schema identifiers and schema names only help you to guess a format. A precise format needs an authoritative reference that you can validate against. If there exists an official XML Schema, this and only this schema defines the format (or the commonly agreed upon subset that you can work with without manually adopting each single data source).

> A single schema may contain multiple namespaces, and there isn't a
> unique identifier for a schema.  For example, any simple Dublin Core
> based syntax must have at least two Namespaces, Dublin Core and the
> wrapper element. SchemaLocation is not unique as there can be many
> copies of the same schema.  A single schema may define multiple root
> elements, such as MODS does with both item and collection level
> elements.

A unique identifier for a schema is helpful because you do not need to actually look up a schema that you already know by its identifier. But it's not a must. If there is no single root namespace, you just should not use a namespace to point to a particular format.

Ok, enough :-)


Jakob Voß <jakob.v...@gbv.de>, skype: nichtich
Verbundzentrale des GBV (VZG) / Common Library Network
Platz der Goettinger Sieben 1, 37073 Göttingen, Germany
+49 (0)551 39-10242, http://www.gbv.de

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