Looking Into Federated Search

A "have to read" item StevenB from ARCLog: "If you are exploring whether or not to get into federated searching at your library take advantage of a good post over at The Distant Librarian about a recent federated search symposium sponsored by the Alberta Library.
There are some good notes on Roy Tennant’s presentation about the implementation of a federated search system for the California Digital Library, a speech by the product manager for Google Scholar, and presentations by federated search system product vendors. It looks like the sort of information that could be of use in the decision-making process" And what if you already have such a system like Metalib from Ex Libris? I will read the notes on Tennant, Google Scholar and the rest and come back with a quick&dirty evaluation.