Brian Del Vecchio wrote a long entry about about splicing a RSS feed by tag and how aggregator developers can create more tag-aware applications. It is possible within the RSS specification, but most feed authors have overlooked how to properly declare tags within their feeds. Flickr does not include categories with its RSS 2.0 feeds and Del.icio.us feeds use Dublin Core subject to provide space-separated tags. Before the feed aggregators can make your life easier we need to all do a better job as content producers to provide valuable information for our users. RSS 2.0 Each RSS 2.0 feed has...