Design of tagging system in a non-relational database
So, I'm looking for resources, ideas, articles on how to structure tags in a non-relational database like bigtable.
I'm currently architecting an application which will most likely run on Google App Engine or similar system. The system is mainly based around one very simple data object (kinda like twitter) but these objects can belong to 0 or more categories/tags. The number of tags per object will normally be pretty low (0-5 tags per object). The user might have quite a bit of tags in use on all his objects together, though. The tags are unique per user, not on system level.
I thought I'd chime in and mention that there aren't really many with much if any experience of non-relational databases that frequent here (hence the lack of response). I did read an article once about how delicious handled tags which would perhaps be of interest.
I don't think non-relational would be necessitated by anything but the largest of websites although I would expect a great deal of use of aggregation tables.