Multiple Query Types in SRU

["LeVan,Ralph" <levan@oclc.org>]

I like the idea of Parameterized Queries.  They are very
OpenSearch-like.  But, they are absolutely not CQL and any attempts to
shove them into CQL are misguided.

We need to squarely address the issue of multiple query types.  Once
that is done, I suspect we'll find a place for Parameterized Queries
(abbreviated PQ from now on because it's a royal pain to type!)

There are a number of ways we could support multiple queries.  I'll list
a few and pick a favorite.

1. We could specify the query type through the use of a controlled list
of query parameters.  "query=" could designate a CQL query and "pquery="
could designate a PQ query.  This would leave the standards group with
the responsibility of controlling the types of queries supported.
Explain would be extended to list the types of queries supported by a
collection (e.g. database).

2. We could have a "queryType" parameter whose value indicated how the
"query" parameter should be interpreted.  Explain would be extended to
list the types of queries supported by a collection and what the default
queryType was.

3. We could take a page from OpenSearch and let the Explain record
define the name of the parameter used for each query type.  So, I could
say that a CQL query was specified with the "cquery" parameter and a PQ
query was specified with the "pq" parameter.  Going this route would
probably require that we come up with a profile document that
recommended some standard parameter names and result in something much
like #1

Personally, I like #3.  I think we need to reconsider all our fixed
parameter names in the light of OpenSearch and determine if they
couldn't be specified in Explain instead.

Ralph