I second the suggestion to give a look at camlistore. It's designed to be a content storage for everything with automatic features extraction; the first use cas

I second the suggestion to give a look at camlistore. It's designed to be a content storage for everything with automatic features extraction; the first use case implemented by the authors is to extract all the metadata from photos as soon as they are uploaded, so you can search for, say, panoramas in Lisbon in the last 3 months. Other document types are already implemented and you can have your own depending on your use case. Coming from a Googler, it's no surprise that the primary interface is "tag stuff, and use search"