This library implements RDF::Repository using the Symas Lightning
MDB key-value database. It is intended to be a basic, durable,
locally-attached quad store, that avails itself of the properties of
LMDB.
RDF::LMDB is also intended to provide a reference implementation
of an architecture for storing RDF in any key-value database, such
that this adapter could be ported, or indeed the data imported, to
other back-ends (e.g. Berkeley DB, LevelDB, Kyoto Cabinet…) without
having to significantly change the design. The only real requirement
for the back-end is some kind of cursor functionality, and the
handling of multi-valued keys.
The system uses binary SHA-256 digests of N-Triples representations of terms and statements. Terms are normalized first before being hashed. The hashes themselves are stored in their binary representation.
The main content of the store is keyed on the hash of a normalized
N-Triples statement (including the terminating .). Its values are
the concatenated hashes of the individual terms:
sha256(s <sp> p <sp> o " .") => sha256(s) sha256(p) sha256(o)
There are four indices that resolve terms to statements, graph, subject, predicate, object, respectively:
sha256(term) => sha256(s <sp> p <sp> o " .")
Finally, there is an index that maps the digests of the terms back to their normalized N-Triples representations:
sha256(term) => term
Generated and deposited in the usual place.
Come on, you know how to do this:
$ gem install rdf-lmdb
Or, download it off rubygems.org.
Bug reports and pull requests are welcome at the GitHub repository.
©2019 Dorian Taylor
This software is provided under the Apache License, 2.0.