NAME

   RDF::NS - Just use popular RDF namespace prefixes from prefix.cc

SYNOPSIS

     use RDF::NS '20160408';              # check at compile time
     my $ns = RDF::NS->new('20160408');   # 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.

SEE ALSO

   There are several other CPAN modules to deal with IRI namespaces, for
   instance RDF::Trine::Namespace, RDF::Trine::NamespaceMap,
   URI::NamespaceMap, RDF::Prefixes, RDF::Simple::NS,
   RDF::RDFa::Parser::Profile::PrefixCC, Class::RDF::NS, XML::Namespace,
   XML::CommonNS etc.

COPYRIGHT AND LICENSE

   This software is copyright (c) 2013- by Jakob Voß.

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

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