man RDF::NS (3): Just use popular RDF namespace prefixes from prefix.cc

SYNOPSIS

use RDF::NS '20150725'; # check at compile time
my $ns = RDF::NS->new('20150725'); # check at runtime
$ns->foaf; # http://xmlns.com/foaf/0.1/
$ns->foaf_Person; # http://xmlns.com/foaf/0.1/Person
$ns->foaf('Person'); # http://xmlns.com/foaf/0.1/Person
$ns->uri('foaf:Person'); # http://xmlns.com/foaf/0.1/Person
use RDF::NS; # get rid if typing '$' by defining a constant
use constant NS => RDF::NS->new('20111208');
NS->foaf_Person; # http://xmlns.com/foaf/0.1/Person
$ns->SPAQRL('foaf'); # PREFIX foaf: <http://xmlns.com/foaf/0.1/>
$ns->TTL('foaf'); # @prefix foaf: <http://xmlns.com/foaf/0.1/> .
$ns->XMLNS('foaf'); # xmlns:foaf="http://xmlns.com/foaf/0.1/"
# load your own mapping from a file
$ns = RDF::NS->new("mapping.txt");
# select particular mappings
%map = $ns->SELECT('rdf,dc,foaf');
$uri = $ns->SELECT('foo|bar|doz'); # returns first existing namespace
# instances of RDF::NS are just blessed hash references
$ns->{'foaf'}; # http://xmlns.com/foaf/0.1/
bless { foaf => 'http://xmlns.com/foaf/0.1/' }, 'RDF::NS';
print (scalar keys %$ns) . "prefixes\n";
$ns->COUNT; # also returns the number of prefixes

DESCRIPTION

Hardcoding URI namespaces and prefixes for RDF applications is neither fun nor maintainable. In the end we all use more or less the same prefix definitions, as collected at <http://prefix.cc>. This module includes all these prefixes as defined at specific snapshots in time. These snapshots correspond to version numbers of this module. By selecting particular versions, you make sure that changes at prefix.cc won't affect your programs.

The command line client rdfns is installed automatically with this module:

  $ rdfns rdf,foaf.ttl
  @prefix foaf: <http://xmlns.com/foaf/0.1/> .
  @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .

This module does not require RDF::Trine, which is recommended nevertheless. (at least version 0.140). If you prefer RDF::NS to return instances of RDF::Trine::Node::Resource instead of plain strings, use RDF::NS::Trine. RDF::NS::URIS is a similar module that returns instances of URI.

The code repository of this module contains an update script <https://github.com/nichtich/RDF-NS/blob/master/update.pl> to download the current prefix-namespace mappings from <http://prefix.cc>.

GENERAL METHODS

In most cases you only need the following lowercase methods.

new ( [ $file_or_date ] [ %options ] )

Create a new namespace mapping from a selected file, date, or hash reference. The special string "any" or the value 1 can be used to get the newest mapping, but you should better select a specific version, as mappings can change, violating backwards compatibility. Supported options include "warn" to enable warnings and "at" to specify a date.

prefix

Returns the namespace for prefix if namespace prefix is defined. For instance "$ns->foaf" returns "http://xmlns.com/foaf/0.1/".

prefix_name

Returns the namespace plus local name, if namespace prefix is defined. For instance "$ns->foaf_Person" returns "http://xmlns.com/foaf/0.1/Person".

uri ( $short | <$URI> )

Expand a prefixed URI, such as "foaf:Person" or "foaf_Person". Alternatively you can expand prefixed URIs with method calls, such as "$ns->foaf_Person". If you pass an URI wrapped in "<" and ">", it will not be expanded but returned as given.

SERIALIZATION METHODS

TTL ( prefix[es] )

Returns a Turtle/Notation3 @prefix definition or a list of such definitions in list context. Prefixes can be passed as single arguments or separated by commas, vertical bars, and spaces.

SPARQL ( prefix[es] )

Returns a SPARQL PREFIX definition or a list of such definitions in list context. Prefixes can be passed as single arguments or separated by commas, vertical bars, and spaces.

XMLNS ( prefix[es] )

Returns an XML namespace declaration or a list of such declarations in list context. Prefixes can be passed as single arguments or separated by commas, vertical bars, and spaces.

TXT ( prefix[es] )

Returns a list of tabular-separated prefix-namespace-mappings.

BEACON ( prefix[es] )

Returns a list of BEACON format prefix definitions (not including prefixes).

LOOKUP METHODS

PREFIX ( $uri )

Get a prefix of a namespace URI, if it is defined. This method does a reverse lookup which is less performant than the other direction. If multiple prefixes are defined, it is not determinstic which one is returned! If you need to call this method frequently and with deterministic response, better create a reverse hash (method REVERSE).

PREFIXES ( $uri )

Get all known prefixes of a namespace URI.

REVERSE

Calling "$ns->REVERSE" is equal to "RDF::SN->new($ns)". See RDF::SN for details.

SELECT ( prefix[es] )

In list context, returns a sorted list of prefix-namespace pairs, which can be used to assign to a hash. In scalar context, returns the namespace of the first prefix that was found. Prefixes can be passed as single arguments or separated by commas, vertical bars, and spaces.

INTERNAL METHODS

SET ( $prefix => $namespaces [, $warn ] )

Set or add a namespace mapping. Errors are ignored unless enabled as warnings with the third argument. Returns true if the mapping was successfully added.

MAP ( $code [, prefix[es] ] )

Internally used to map particular or all prefixes. Prefixes can be selected as single arguments or separated by commas, vertical bars, and spaces. In scalar context, $_ is set to the first existing prefix (if found) and $code is called. In list context, found prefixes are sorted at mapped with $code.

GET ( $uri )

This method is used internally to create URIs as return value of the URI method and all lowercase shortcut methods, such as "foaf_Person". By default it just returns $uri unmodified.

COPYRIGHT AND LICENSE

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.