Lagra

RDF for Erlang.

Description

Lagra is an RDF library for Erlang. It supports the serialization and deserialization of various RDF formats, with the option of incremental parsing, so that large graph files can be processed in a streaming fashion. Lagra also provides an API for querying and manipulating (small) RDF graphs directly in memory.

It supports the following RDF serialization formats:

• N-Triples (read/write)
• N-Quads (read only)
• Turtle (read/write)

Why "lagra"?

It's for managing LAbelled GRAphs.

Documentation

API documentation is available. Comprehensive usage documentation and tutorial documentation has not yet been written (it's early days).

Quick example

1> application:start(lagra).
ok
2> G = lagra:create_store(trivial).
<0.88.0>
3> {ok, File} = file:open("doap.ttl", [read, {encoding, utf8}]).
{ok,<0.90.0>}
4> ok = lagra:parse(G, File, turtle, #{base => "http://carfax.org.uk/software/lagra/"}).
ok
5> lagra:find_all_t(G, {'_', '_', lagra_model:new_iri(<<"http://usefulinc.com/ns/doap#GitRepository">>)).
[{{iri,<<"http://git.darksatanic.net/repo/lagra.git/">>},
  {iri,<<"http://www.w3.org/1999/02/22-rdf-syntax-ns#type">>},
  {iri,<<"http://usefulinc.com/ns/doap#GitRepository">>}},
 {{iri,<<"https://github.com/darkling/lagra.git">>},
  {iri,<<"http://www.w3.org/1999/02/22-rdf-syntax-ns#type">>},
  {iri,<<"http://usefulinc.com/ns/doap#GitRepository">>}}]
6> lagra:destroy_store(G).
ok

Future plans

In no particular order:

• Write Turtle more elegantly
• Read/write JSON-LD
• Read/write RDF/XML
• Use a remote SPARQL/SPARUL endpoint as a store
• Improve the in-memory store, so that it is usable for more than trivial-sized graphs
• Add more functions for walking the triple graph
• Namespace management (parse namespaces from input documents; serialize with supplied namespace map)

I have an immediate need for the first two items on the above list, and will shortly be needing the remote store functionality, so they have the highest priority.

Contact

Author

Hugo Mills <hugo@carfax.org.uk>