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> Date: Fri, 5 Nov 2004 06:43:01 -0500
> From: Eliot Christian <[log in to unmask]>
>
>> A clarification: there is NO "inheritance" of context sets.  This
>> paradigm is a holdover from Z39.50 version 2, when all the
>> attributes in a Type-1 query had to be taken from the same
>> attribute set, with ugly results such as the GILS and CIMI sets
>> both importing BIB-1 wholesale.  But in Z39.50 version 3, and of
>> course in SRW/U, there is no such limitation: indexes from
>> different context sets can be freely mixed, so there should ideally
>> be _no_ duplication of indexes between context sets.
>
> The word "inheriting" may have been a poor choice. In the GILS
> Context Set I would like to re-use some indexes defined in other
> context sets, as a deliberate strategy to enhance interoperability.

A context set cannot reuse index from another set.  A _profile_ can,
though; we need to make a very clear distinction between a context set
(which is just a sety of indexes, relation modifiers and boolean
modifiers), and a profile (which tells you which indexes etc. to use
from which sets, and how they work together).

For a trivial but hopefully instructive example, see the Bath Profile
for SRW, version 2.0, available at
        http://zing.z3950.org/srw/bath/2.0/
As you will see, the context set (though physically contained within
the same document) stands alone, and any profile may reuse indexes
from the set.  But the profile uses, and discusses, indexes from
several sets.

There's an even clearer example in the Zthes Profile for SRW, at
        http://zthes.z3950.org/srw/zthes-srw-0.5.html
which doesn't contain the Zthes context set at all, but merely points
to it, just as it does for the CQL, Red and DC sets.  The context set
itself is in the separate document
        http://zthes.z3950.org/cql/1.0/

Similarly, you need to make two separate documents for GILS-over-SRW.
There's a short one, the GILS context set, which will define some
indexes and maybe relation modifiers or boolean modifiers; and the
longer one will be the GILS Profile, which refers to the GILS context
set as one among many.

Sorry if this is patronising, it's not meant to be; but it's a very
important distinction, and we need to make sure we are clear on it.

Discussion of dc.creator's repurposed semantics to follow ...

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/o ) \/  Mike Taylor  <[log in to unmask]>  http://www.miketaylor.org.uk
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