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To sum up, the "photocasting" feature centers around a single undocumented extension element in a namespace that doesn't need to be declared. iPhoto 6 doesn't understand the first thing about HTTP, the first thing about XML, or the first thing about RSS. It ignores features of HTTP that Netscape 4 supported in 1996, and mis-implements features of XML that Microsoft got right in 1997. It ignores 95% of RSS and Atom and gets most of the remaining 5% wrong.