From metasearch to distributed information environments (Lorcan Dempsy) is a good overview on metasearch in the academic enviroment, and search/metadata APIs.
I looked at a number of the documents, including the first two PowerPoint files and the information on MXG. All worth looking at.
In terms of meta/federated search, those schools (first two PowerPoints) are definitely making leaps forward. The commercial and academic worlds are beginning to learn from each other. The improvements are great, but need to be much greater.
The MXG (.doc file) proposal looks to me like an attempt to make a simpler but not as great version of SRU, which tried to do the same for Z39.50. Which is good news, the authors seem to have the right attitude. I also like how they’ve made levels of the specification, each of which is more complicated, and thus closer to SRU (that last is SRU).
If I were them I’d think hard about OpenSearch. It is a much simpler specification (clearly not originating from the academic world) which accomplishes less than even MXG Level 1. But not that much less, considering how much easier it is to use.
One specific thing that OpenSearch does that the other specifications don’t, is allow search engines to use their own URL variables instead of predefined ones. It looks fairly trivial to me for this concept to be integrated into the SRU/MXG specifications.
Back to academic ‘multi’ search tools, there is UWhub, my personal project. Right now it does web search and image search (just added that this week), but I would definitely like to expand this to include searching within the school’s library, among other things.