RE: JW11: single scope

> If I remember correctly, we deliberately decided to limit the
> scope list to one element for the first version to avoid defining and
> debating three valued elimination -- the obvious straightforward extension
> of three valued logic used in other industry standards to handle
> cross-repository queries.

I was thinking more in terms of performing a query on, say, multiple
hierarchies on the same server, making the assumption that all of the
hierarchies contained resources with the same properties.

For example, if I have some resources set up as follows:

        src/
        src/module1/
        src/module2/
        src/module3/

If I want to do a search only on the src/module2/ and src/module3/
hierarchies, I would have to submit two DASL requests in the current
proposal.

> That is necessary, because the query
> schemas of multiple repositories don't have to be identical, and
> the issue of handling queries that are partially defined arises
> immediately.

I agree, but I don't see a query directed to a single DASL arbiter running
into this problem.  Perhaps if a DASL search arbiter were sitting on top of
a DMA interface this would occur...

> First issue: Do you want your query to be defined on the intersection
> of the query schemas, or their union? That must be specified.
> The intersection may be too small to be useful, especially for
> repositories that don't implement QSD. The union case must
> obviously handle queries that are only partially defined on its
> constituent repositories.

Since all DAV resources have to support a known set of predefined
properties, doing a search on the intersection can be quite useful.

- Jim

Received on Tuesday, 20 July 1999 17:54:16 UTC