SNA methods
   - matrix support?

Server: models should take catalog parameter to only look there for repos

Catalog: understand more POSIX modes for repository method

Repository: context (named graphs) and multiple graph queries
Repository: support proper tuple lists for sparql
Repository: sparql support ASK, SELECT, CONSTRUCT, DESCRIBE

support {} options for add/replace

federate support

date queries

persistent queries

is_writable for repos
