Creating a Firefox search plugin

I usually create plugins for my favorite search engines (aside from what's already rolled with the browser).

I've recently made one for the new kid on the block, Wolfram|Alpha. While not technically a "search engine", Wolfram|Alpha does offer some interesting possibilties (its goals are rather ambitious — much like Google's plan to "organize all the world's information" — but I would love to see it succeed).

But I digress. Firefox search plugins are created using an XML file in the OpenSearch format, as below:

(The tags are specified and described here in more details.)

After hosting the XML file somewhere, you can either have the plugin autodiscovered by placing the following in the HEAD of your HTML:

<link rel="search" type="application/opensearchdescription+xml" title="[description]" href="[XML URI]"></link>

or through the window.external.AddSearchProvider() DOM method:

window.external.AddSearchProvider([XML URI]);

While Wolfram|Alpha does offer its own search add-on, here's mine for you to try.