RDF::Closure::DatatypeHandling(3pm)

NAME
RDF::Closure::DatatypeHandling - validate and canonicalise typed literals

ANALOGOUS PYTHON
RDFClosure/DatatypeHandling.py

DESCRIPTION
Provides datatype handling functions for OWL 2 RL and RDFS datatypes.

  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;

SEE ALSO
RDF::Closure.

<http://www.perlrdf.org/>.

AUTHOR
Toby Inkster <tobyink@cpan.org>.

COPYRIGHT
Copyright 2008-2011 Ivan Herman

Copyright 2011-2012 Toby Inkster

This library is free software; you can redistribute it and/or modify it under any of the following licences:

•   The Artistic License 1.0 <http://www.perlfoundation.org/artistic_license_1_0>.

•   The GNU General Public License Version 1 <http://www.gnu.org/licenses/old-licenses/gpl-1.0.txt>, or (at your option) any later version.

•   The W3C Software Notice and License <http://www.w3.org/Consortium/Legal/2002/copyright-software-20021231>.

•   The Clarified Artistic License <http://www.ncftp.com/ncftp/doc/LICENSE.txt>.

DISCLAIMER OF WARRANTIES
THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.