Mahout: How does the timestamp influence recommendations

Question

While building recommendations with Apache Mahout, I've noticed that one can add a timestamp to DataModel (e.g. FileDataModel or PostgreSQLJDBCDataModel).

Is this value used internally to improve the recommendations (maybe to weight preference)? Or is it just to manually get the timestamp and do some own calculations? If it is only for own use, how does it affect the performance/memory usage on large scale?

Answer 1

None of the supplied implementations use it, but you could write one that does.