Some thoughts on SRU and OpenSearch in response to some off-hand comments Eric Lease Morgan made comparing the two. Disclaimer: I am not actually that familiar with SRU.
I have been spending some time with the OpenSearch spec lately in anticipation of using it in a particular future project I have in mind. (A generic ‘saved searches’ store as part of Xerxes).
I’ve been quite impressed with it. I think the idea of merging SRU into OpenSearch is a good one.
It’s not really true to say that “OpenSearch returns an RSS-like data stream” — rather an OpenSearch description can specify exactly what format is returned using a MIME type, and can even specify different URLs for retrieving different formats. So I think it’s rather compatible with SRU here. There’s no reason an OpenSearch description can’t declare results returned in MARC-XML or anything else. (I hope MARCXML, MODS, etc, have declared mime types? If not they need to asap for a billion reasons!)
Also, while an OpenSearch description document doesn’t declare any particular syntax for it’s query, there’s no reason an OpenSearch query _couldn’t_ be in CQL.
It would seem useful to me to extend OpenSearch to allow a description document to specify that CQL is supported, and specify what search indexes the server provides, or any other CQL-related metadata.
One of the most useful parts of OpenSearch is how it allows easy extensibility using custom namespaces. I am actually not that familiar with SRU, and haven’t read that OASIS document Eric mentions yet, but I hope they take the approach of trying to fit SRU into the existing OpenSearch standard, rather than creating a new ‘umbrella’ standard on top of it. I think the OpenSearch standard would be quite suited to this. Perhaps a CQL or SRU extension to OpenSearch.
I perused the OpenSearch listserv recently, and I didn’t see any mention of OASIS or SRU, but I wasn’t looking for it either. I hope the OASIS folks are actually talking to the OpenSearch folks about this, rather than just doing things in their own silo. The OpenSearch folks seem to me to be quite on top of things, and interested in making sure OpenSearch supports new use cases in the ‘right’ way.