Data Modelling Advice for Blog Tagging system on Google App Engine

Thanks to both of you for your suggestions. I've implemented (first iteration) as follows. Not sure if it's the best approach, but it's working.

Class A = Articles. Has a StringListProperty which can be queried on it's list elements

Class B = Tags. One entity per tag, also keeps a running count of the total number of articles using each tag.

Data modifications to A are accompanied by maintenance work on B. Thinking that counts being pre-computed is a good approach in a read-heavy environment.

counts being pre-computed is not only practical, but also necessary because the count() function returns a maximum of 1000. if write-contention might be an issue, make sure to check out the sharded counter example.

http://code.google.com/appengine/articles/sharding_counters.html