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RDF-Closure-0.001
River stage zero No dependents
/ RDF::Closure::DatatypeHandling

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:

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.