RDF::Closure::DatatypeHandling(3pm)

Functional Interface

This module can export four functions:

•

"literal_canonical($lit)"

Given an RDF::Trine::Node::Literal, returns a literal with the canonical lexical value for its given datatype. If the literal is not a valid lexical form for its datatype throws an Error.

If the literal is a plain literal, returns an rdf:PlainLiteral typed literal; if the literal is of an unrecognised datatype, simply returns the original literal.

Note that as per OWL 2 RL rules, xsd:dateTime literals are not shifted to UTC, even though XSD says that UTC is the canonical form. By setting the "force_utc" to true, you can force XSD-style canonicalisation. (See the object-oriented interface.)

•

"literal_canonical_safe($lit)"

As per "literal_canonical", but in the case where a literal is not a valid lexical form, simply returns the original literal.

•

"literal_valid($lit)"

Returns true iff the literal is a valid lexical form for its datatype. An example of an invalid literal might be:

  "2011-02-29"^^xsd:date

•

"literals_identical($lit1, $lit2)"

Returns true iff the two literals are identical according to OWL 2 RL. Here are some example pairs that are identical:

  # integers and decimals are drawn from the same pool of values
  "1.000"^^xsd:decimal
  "1"^^xsd:integer
  
  # different ways of writing the same datetime
  "2010-01-01T12:00:00.000Z"^^xsd:dateTime
  "2010-01-01T12:00:00+00:00"^^xsd:dateTime

Here are some example literals that are not identical:

  # floats and decimals are drawn from different pools of values
  "1.000"^^xsd:float
  "1"^^xsd:integer
  
  # according to OWL 2 these are "equal but not identical".
  "2010-01-01T12:00:00+00:00"^^xsd:dateTime
  "2010-01-01T11:00:00-01:00"^^xsd:dateTime

This latter example is affected by "force_utc".

•

"literal_to_perl($lit)"

Returns a scalar value for the literal, or an appropriate object with overloaded operators (e.g. DateTime, Math::BigInt).

Variables $RDF, $RDFS, $OWL and $XSD may also be exported as a convenience. These are RDF::Trine::Namespace objects. Don't modify them.

Object-Oriented Interface

  use RDF::Trine;
  use RDF::Closure::DatatypeHandling qw[$XSD];
  
  my $lit     = RDF::Trine::Node::Literal->new(
    "2010-01-01T11:00:00-01:00", undef, $XSD->dateTime);
  my $handler = RDF::Closure::DatatypeHandling->new(force_utc => 1);
  print $handler->literal_canonical($lit)->as_ntriples;