Article:		Never Mind the Namespaces: An XSLT RSS Client
Subject:		Aggregation versus merely displaying
Date:		2003-01-09 08:58:12
From:		Damian Cugley
Displaying RSS feeds organized by their originator is simple enough; that's what my.netscape.com did in the olden days. Displaying them organized by DATE is harder. Much harder, because RSS 0.91 does not include per-item date fields at all! The only solution to this is to poll RSS feeds periodically and see if you can spot additions; this way you can tag items with the date you discovered them, which is approximatly the same as their publication date. This does not really work if items can be expected to change, since in that case you don't have any deterministic way to work out if a given item is new or is an old item edited. Giving items their own permanent URIs helps, but that is also not an RSS 0.91 feature, alas! On top of this, regular polling makes for bandwidth issues. Your program had better know about caching and ETags and If-Modified-Since and the various which-RSS-has-changed-recently services if it is to be a good WWW citizen. All of this means that a really good RSS aggregator has to be a fairly tricky piece of software. Don't get me wrong, XSLT is a great tool (and I use it every day) but RSS as a format has too many features that defeat any elegant solution... :-(

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