# Redland RDF Application Framework - Perl RDF::Redland::Node Class

## NAME

RDF::Redland::Node - Redland RDF Node (RDF Resource, Property, Literal) Class

## SYNOPSIS

      use RDF::Redland;
      my $node1=new RDF::Redland::Node("Hello, World!");
      my $node2=new RDF::Redland::Node($uri); # $uri is an RDF::Redland::URI
      my $node3=$node2->clone;

      my $node4=new RDF::Redland::URINode("http://example.com/";);
      my $node5=new RDF::Redland::LiteralNode("Hello, World!");
      my $node6=new RDF::Redland::XMLLiteral("<tag>content</tag>");
      my $node7=new RDF::Redland::BlankNode("genid1");

      # alternate more verbose ways:
      my $node4=RDF::Redland::Node->new_from_uri("http://example.com/";);
      my $node5=RDF::Redland::Node->new_literal("Hello, World!");
      my $node6=RDF::Redland::Node->new_xml_literal("<tag>content</tag>");
      my $node7=RDF::Redland::Node->new_from_blank_identifier("genid1");
      ...

      print $node4->uri->as_string,"\n";  # Using RDF::Redland::URI::as_string
      print $node5->literal_value_as_latin1,"\n";

## DESCRIPTION

This class represents RDF URIs, literals and blank nodes in the RDF graph.

## CONSTRUCTORS

new [STRING | URI | NODE]

  Create a new URI node, literal node or copy an existing node.

  If a literal STRING is given, make a plain literal node. If a the argument is of type URI (perl URI or RDF::Redland::URI), make a resource node.

  Otherwise if the argument is an RDF::Redland::Node NODE, copy it.

new_from_uri URI

  Create a new URI node. URI can be either a RDF::Redland::URI object, a perl URI class or a literal string.

  An alternative is:

        new RDF::Redland::URINode("http://example.org/";);

new_literal STRING [DATATYPE [XML_LANGUAGE]]

  Create a new literal node for a literal value STRING. Optional datatype URI DATATYPE (RDF::Redland::URI, perl URI or string) and language (xml:lang attribute) XML_LANGUAGE may also be given.

  An alternative is:

         new RDF::Redland::LiteralNode("Hello, World!");
         new RDF::Redland::LiteralNode("Bonjour monde!", undef, "fr");

new_xml_literal STRING

  Create a new XML datatyped literal node for the XML in STRING.

  An alternative is:

        new RDF::Redland::XMLLiteral("<tag>content</tag>");

new_from_blank_identifier IDENTIFIER

  Create a new blank node with blank node identifier IDENTIFIER.

  An alternative is:

        new RDF::Redland::BlankNode("id");

clone

  Copy a RDF::Redland::Node.

## METHODS

uri

  Get the current URI of the node as an RDF::Redland::URI object.

blank_identifier

  Get the current blank identifier of the node

type

  Get the node type. It is recommended to use the is_resource, is_literal or is_blank methods in preference to this (both simpler and quicker).

  The current list of types that are supported are:

        $RDF::Redland::Node::Type_Resource
        $RDF::Redland::Node::Type_Literal
        $RDF::Redland::Node::Type_Blank

  Example:

        if ($node->type == $RDF::Redland::Node::Type_Resource) {
          print "Node is a resource with URI ", $node->uri->as_string, "\n";
        } else {
          ...
        }

is_resource

  Return true if node is a resource (with a URI)

is_literal

  Return true if node is a literal

is_blank

  Return true if node is a blank nodeID

literal_value

  Get the node literal value string as UTF-8 (when the node is of type $RDF::Redland::Node::Type_Literal)

literal_value_as_latin1

  Get the node literal value string converted from UTF-8 to ISO Latin-1 (when the node is of type $RDF::Redland::Node::Type_Literal)

literal_value_language

  Get the node literal XML language (when the node is of type $RDF::Redland::Node::Type_Literal) or undef if not present.

literal_value_is_wf_xml

  Return non 0 if the literal string is well formed XML (when the node is of type $RDF::Redland::Node::Type_Literal).

literal_datatype

  Return the RDF::Redland::URI of the literal datatype or undef if it is not a datatype.

as_string

  Return the RDF::Redland::Node formatted as a string (UTF-8 encoded).

equals NODE

  Return non zero if this node is equal to NODE

## OLDER METHODS

new_from_literal STRING XML_LANGUAGE IS_WF

  Create a new RDF::Redland::Node object for a literal value STRING with XML language (xml:lang attribute) XML_LANGUAGE and if content is well formed XML, when IS_WF is non 0. XML_LANGUAGE is optional can can be set to undef.

  This method remains but using new_literal is prefered. Instead, for plain literals use:

        $node=new RDF::Redland::Node("blah")

new_from_typed_literal STRING [DATATYPE [XML_LANGUAGE]]

  Renamed to new_literal with same arguments.

new_from_uri_string URI_STRING

  Create a new RDF::Redland::Node object for a resource with URI URI_STRING. It is equivalent to use the shorter:

        $a=new RDF::Redland::Node->new_from_uri($uri_string)

new_from_node NODE

  Create a new RDF::Redland::Node object from existing RDF::Redland::Node NODE (copy constructor). It is equivalent to use:

        $new_node=$old_node->clone

## SEE ALSO

the RDF::Redland::Statement manpage

## AUTHOR

Dave Beckett - http://www.dajobe.org/

(C) Copyright 2000-2011 Dave Beckett, (C) Copyright 2000-2005 University of Bristol