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.