Is there a nosql store that also allows for relationships between stored entities? <p>I am looking for nosql key value stores that also provide for storing/maintaining relationships between stored entities. I know Google App Engine's datastore allows for owned and unowned relationships between entities. Does any of the popular nosql store's provide something similar? </p> <p>Even though most of them are schema less, are there methods to appropriate relationships onto a key value store? </p>