I took some time this evening to whip up a dynamic RSS Search page using A9's new OpenSearch standard. After working out some trouble with some wayward characters before my xml declaration (thanks Erik!), it was up and running in no time. It's a really simple concept actually: return dynamic RSS content in response to a query, with parameters for paging. That's it! But the way A9 uses it makes it kinda cool. If you remember I was playing with dynamic RSS results before with the Mobdex stuff, so if it wasn't already painless to use their three new tags, having most of the work done already made it even more so.
I really think this is the future of RSS feeds - the subscriber will pass parameters that say exactly what they are looking for, and the server will pass back only the items that qualify and nothing more. Not just for searches, but for all RSS traffic. Using HTTP headers is fine in general, but if I have 10 items in my feed and I add one more, when an aggregator grabs the updated page, it gets 9 old items and one new one instead of just the one new item it doesn't have. This was what everyone was talking about at Camp Foo last year and I think it's a no brainer in the future. The OpenSearch stuff is just a manifestation of this way of thinking about RSS.
If you'd like to play with the new feed search RSS you can. The url looks like this: http://www.russellbeattie.com/notebook/feedsearch?q=nokia&start=1&count=10 . It's not a particularly robust search page and the error handling is non-existant, but it's good enough to play. :-) Besides, I got my picture on the first page of the A9 columns page (for now).