We have added a basic REST API for managing multiple repositories on a bigdata Journal or Federation. The API is documented on the wiki. There is also a Java client for the API (RemoteRepositoryManager).
Bigdata has always supported multiple triple stores or quad stores per backend database instance. Using the Multi-Tenancy extensions to the NanoSparqlServer you can now create, list, and describe the available sparql end points. Each triple or quad store instance corresponds to a data set in the API. Each data set is identified by a namespace. The default namespace is kb. You can have LOTS of named data sets. They are stored in a highly scalable index, just like everything else. You can also mix and match triple and quad stores in the same database instance, or have different features for each triple store or quad store. However, the defaults in effect when the database instance was created will be inherited by each new triple store or quad store instance.
The API provides the basic mechanisms for listing the known namespaces, giving you a simple VoID description of each known data set. You can use that information to obtain the SPARQL Service Description of the data set, which includes a detailed VoID description complete with a variety of interesting statistics.
See https://sourceforge.net/apps/mediawiki/bigdata/index.php?title=NanoSparqlServer for more information on the API.
This feature is in the 1.2 maintenance branch (branches/BIGDATA_RELEASE_1_2_0). It will be part of the 1.2.2 maintenance release.