Simon Fell > Its just code
Bill Kearney has some comments on my earlier suggestion about aggregators using ETags. In response to Bills points, both Apache and IIS will automatically generate ETags for static files, IIS will also serve a Last-Modified header in this case as well [haven't checked this on Apache]. You only make a single pass, supplying the last etag in the next request, this requires you to store the etag value between agregator passes [as does an approach based on Last-Modified, If-Modified-Since]. In the specific case of RSS you'll propbably not see any issues using Last-Modified, If-Modified-Since rather than Etag and If-None-Match, however for HTTP/1.1 Etag is the preffered approach [particularly if you want to support resumable downloads]. In either case you need to store some additional data between requests, so I don't see that one approach is any harder than the other. How easy this is, largely depends on what HTTP client code you're using, as Joe points out this is pretty easy in .NET, I've also done this with libcURL, where its equally easy, YMMV.
There's a new build of the WSDL Wizard for PocketSOAP beta available.