When developing web applications when would you use a Graph database versus a Document database?

Question

I am developing a web-based application using Rails. I am debating between using a Graph Database, such as InfoGrid, or a Document Database, such as MongoDB.

My applica

Answer 1

When connecting related documents by edges, will you get a shallow or a deep graph? I think the answer to that question is important when deciding between graphdbs and documentdbs. See Square Pegs and Round Holes in the NOSQL World by Jim Webber for thoughts along these lines.