The question is two fold:
The first question is discussed here resource discovery. For the 2nd question see Using media rss to syndicate and share media.
The ideas described on this page are relevant, because we're using them for two projects:
The portals contain about 7500 data sets, and we need to have a good syndication standard to be able to share metadata efficiently.
More info about portal ideas: http://www.steeple.org.uk/wiki/Portal
Dublin core, OAI, ORE:
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