Are the Spark efforts supporting all Mahout Vector types? Named, Property Vectors? It occurred to me that data frames in R is a related but more general solution. If all rows and columns of a DRM and their coresponding Vectors (row or column vectors) were to support arbitrary properties attached to them in such a way that they are preserved during transpose, Vector extraction, and any other operations that make sense there would be a huge benefit for users.
One of the constant problems with input to Mahout is translation of IDs. External to Mahout going in, Mahout to external coming out. Most of this would be unneeded if Mahout supported data frames, some would be avoided by supporting named or property vectors universally.
