I think (idiot warning here) the way to do this will be to implement NoSQL features such as map-reduce when compute is available.
In the mean time you can run something local and sync with the network using client side scripts (in JavaScript). Browsers already support client side databases these days, plus you have things like PouchDb.
This is how remoteStorage.js works for example, and some of you have seen and played with a demo app using this on the earlier test networks (see my favourite drinks and litewrite).