Creating a user controlled data service with Google App engine

I am designing a to-do list manager for the iPhone using GAE as the back end. My end goal is to create user sharable lists, and I was looking for some advice/examples of how to go about designing something like that. I know the google user API provides functionality for authenticating users, but from what I can tell any additional user management would be something I would need to implement myself.

Can something like this be done by simply adding usernames to a list that is a property of the data I want to share? I am guessing I am oversimp开发者_开发技巧lifying things, but any suggestions would be appreciated.

Thanks

you're right, app engine doesn't have any built in support for user ACLs or permissions, and a few quick web searches didn't immediately turn up any obvious open source libraries.

how to implement full-fledged permissions and ACLs for group sharing is definitely a nontrivial design question. there are a number of other questions here about it.

having said that, as a very rough first pass, you're probably on the right track with storing lists of users. i'd suggest that you abstract the list into separate Group entities, and attach those to yor data instead, so that users can define groups once instead of for every piece of data. i'd also consider storing separate lists of groups that can read vs write. finally, i'd store User properties in the group entities, instead of string usernames or email addresses.