NAME

NAME
RDF::Prefixes - simple way to turn URIs into QNames

SYNOPSIS
my $context = RDF::Prefixes->new;
say $context->qname('http://purl.org/dc/terms/title'); # dc:title
say $context->qname('http://example.net/rdf/dc#title'); # dc2:title
say $context->turtle; # @prefix dc: <http://purl.org/dc/terms/> .
# @prefix dc2: <http://example.net/rdf/dc#> .

DESCRIPTION
This module is not so much for managing namespaces/prefixes in code (see
RDF::Trine::NamespaceMap for that), but as a helper for code that
serialises data using namespaces.

It generates pretty prefixes, reducing "http://purl.org/dc/terms/" to "dc"
rather than something too generic like like "ns01", and provides a context
for keeping track of namespaces already used, so that when
"http://purl.org/dc/elements/1.1/" is encountered, it won't stomp on the
previous definition of "dc".

Constructor
`new(\%suggestions, \%options)`
Creates a new RDF prefix context.

Suggestions for prefix mappings may be given, but there's no guarantee
that they'll be used.

The only option right now is 'syntax' that is used by the to_string
method.

Both hashrefs are optional.

Methods
`get_prefix($uri)`
Gets the prefix associated with a URI. e.g.
`get_prefix('http://purl.org/dc/terms/')` might return 'dc'.

`get_qname($uri)`
Gets a QName for a URI. e.g.
`get_qname('http://purl.org/dc/terms/title')` might return 'dc:title'.

Some URIs cannot be converted to QNames. In these cases, undef is
returned.

`get_curie($uri)`
As per `get_qname`, but allows for more relaxed return values,
suitable for RDFa, Turtle or Notation 3, but not RDF/XML. Should never
need to return undef.

`preview_prefix($uri)`, `preview_qname($uri)`, `preview_curie($uri)`
As per the "get" versions of these methods, but doesn't modify the
context.

`to_hashref`
Returns a hashref of prefix mappings used so far. This is not
especially necessary as the object may be treated as a hashref
directly:

foreach my $prefix (keys %$context)
{
printf("%s => %s\n", $prefix, $context->{$prefix});
}

`TO_JSON`
A synonym for to_hashref, provided for the benefit of the JSON
package.

`rdfa`
Return the same data as `to_hashref`, but as a string suitable for
placing in an RDFa 1.1 prefix attribute.

`sparql`
Return the same data as `to_hashref`, but as a string suitable for
prefixing a SPARQL query.

`turtle`
Return the same data as `to_hashref`, but as a string suitable for
prefixing a Turtle or Notation 3 file.

`xmlns`
Return the same data as `to_hashref`, but as a string of xmlns
attributes, suitable for use with RDF/XML or RDFa.

`to_string`
Calls either `rdfa`, `sparql`, `turtle` (the default) or `xmlns`,
based on the 'syntax' option passed to the constructor. This module
overloads the stringification operator, so explicitly calling
to_string is rarely necessary.

my $context = RDF::Prefixes->new({}, {syntax=>'turtle'});
my $dc_title = 'http://purl.org/dc/terms/title';
print "# Prefixes\n" . $context;

Internationalisation
Strings passed to and from this module are expected to be utf8 character
strings, not byte strings. This is not explicitly checked for, but will be
checked in a future version, so be warned!

URIs containing non-Latin characters should "just work".

BUGS
Please report any bugs to <http://rt.cpan.org/>.

AUTHOR
Toby Inkster <[email protected]>.

COPYRIGHT
Copyright 2010-2013 Toby Inkster

This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.

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.