Back in the day, I used to work on the Mycroft Project. At the time, only Firefox/Netscape could actually used these plugins as they were based on Apple's Sherlock specification (Mycroft is Sherlock Holmes' brother, btw). These plugins have been a staple in the Firefox browser, but the Sherlock spec was a little arcane. More recently, both Firefox and IE have implemented support for the OpenSearch specification. I have to say that the OpenSearchDescription is a significant update (at least from a readability standpoint) than Sherlock.
A few years ago, I had written a bunch of Sherlock plugins for searching various library catalogs. Those pretty much lay dormant until I was talking with my student worker this last semester and he got quite excited about these, and wondered if there might be a way to also search the databases the library subscribes to, and provide off-campus access to these through our proxy server. This code is in a very basic stage right now, but essentially what I did was create a database driven application in PHP that generates OpenSearch XML for various targets to search against.
Right now, this only supports HTTP GET requests (POST parameters require an additional table), but here's the DDL:
You don't need all of these fields for every record, and here is some useful records...
Apparently I wrote the queries with MDB2, I've since moved most of my interactions to Zend Db (you should be able to write that part pretty quickly) and just dump the names of the plugins in the tableon a view:
The add code is straight-forward
If I get some time soon, I’ll wrap this up into a package; rudimentary, but a decent start to your own app!