Release 3.1.2

Important new features include provisional support for RDF* and updates to query optimization.

• Cleanup etc/doap and references for developers.
  • Now uses https://unlicense.org/1.0/ for dap:license.
• RDF::Vocabulary
  • Update Vocabulary writer to output vocabulary classes that better document the vocabulary and reduce Yardoc errors.
  • Don't try to document vocabulary terms which aren't valid as Ruby attribute names.
  • Optimize Vocabulary.expand_pname to use Vocabulary.vocab_map, to look up terms by their standard prefix.
    • Vocabulary.vocap_map uses re-wored RDF::VOCABS, and is overrided by rdf-vocab, if it is included.
    • Also added Vocabulary.from_sym, which will return the vocabulary associated with the class_name symbol (e.g., RDF::Vocabulary.from_sym(:OWL) => RDF::OWL.
    • Adds RDF::Vocabulary.limit_vocabs which is used to limit the vocabularies returned by RDF::Vocabulary.each and can substantially reduce load time when the rdf-vocabs gem is used.
• Core Model
  • Make RDF::Statement an RDF::Resource, which allows a statement to appear as either the subject or object of another statement.
  • Update N-Triples and N-Quads readers and writers to accept and emit such statements; for the reader this requires using the rdfstar option, with value of either :PR or :SA.
  • An RDF::Enumerable may express support for by responding with true to #supports?(:rdfstar). The memory-based RDF::Repository supports RDF*.
  • Add Statement#embedded? to discriminate statements including statements.
  • Check for support for rdfstar before inserting embedded statements.
• RDF::Query
  • Support query patterns with recursive sub-patterns for subject or object.
    • Variables include those from sub-patterns.
    • Added Pattern#eql? which does recursive checks on sub-patterns.
    • Solution binding also binds to sub-patterns.
    • In Repository#query_pattern, consider recursive patterns for subject or object to match against recursive statements for subject or object.
    • Merging solutions also adds solutions found by binding recursive patterns to statements.
      ( This supports the SPARQL BIND(<<?a ?b ?c>> AS ?t) pattern).
  • Order Query::Solutions#variable_names based on Query::Solutions#project.
  • Binding to a variable now requires a solution (term is deprecated). This makes binding consistent with other uses.
  • In Solution#merge! don't merge a pattern over a statement. (BIND embedded triple use case).
  • Add :optimize option to Query.execute.
  • Remember graph_name when dupping a Query.
  • Invert costs in Pattern, as it ends up that favoring objects before subjects is much more expensive.