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.\" ========================================================================
.\"
.IX Title "RDF::Lazy 3pm"
.TH RDF::Lazy 3pm "2019-02-20" "perl v5.28.1" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH "NAME"
RDF::Lazy \- Lazy typing access to RDF data
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&  ### How to create a graph
\&
\&  $g = RDF::Lazy\->new(
\&     rdf        => $data,    # RDF::Trine::Model or ::Store (by reference)
\&     namespaces => {         # namespace prefix, RDF::NS or RDF::Trine::NamespaceMap
\&         foaf => \*(Aqhttp://xmlns.com/foaf/0.1/\*(Aq,
\&         rdf  => "http://www.w3.org/1999/02/22\-rdf\-syntax\-ns#",
\&         xsd  => "http://www.w3.org/2001/XMLSchema#",
\&     }
\&  );
\&
\&  $g = RDF::Lazy\->new( $data, format => \*(Aqturtle\*(Aq );  # parse RDF/Turtle
\&  $g = RDF::Lazy\->new( $data, format => \*(Aqrdfxml\*(Aq );  # parse RDF/XML
\&  $g = RDF::Lazy\->new( "http://example.org/" );      # retrieve LOD
\&
\&  ### How to get nodes
\&
\&  $p = $g\->resource(\*(Aqhttp://xmlns.com/foaf/0.1/Person\*(Aq); # get node
\&  $p = $g\->uri(\*(Aq<http://xmlns.com/foaf/0.1/Person>\*(Aq);    # alternatively
\&  $p = $g\->uri(\*(Aqfoaf:Person);                            # same but lazier
\&  $p = $g\->foaf_Person;                                  # same but laziest
\&
\&  $l = $g\->literal(\*(AqAlice\*(Aq);              # get literal node
\&  $l = $g\->literal(\*(AqAlice\*(Aq,\*(Aqen\*(Aq);         # get literal node with language
\&  $l = $g\->literal(\*(Aq123\*(Aq,\*(Aqxsd:integer\*(Aq);  # get literal node with datatype
\&
\&  $b = $g\->blank(\*(Aqx123\*(Aq);   # get blank node
\&  $b = $g\->blank;           # get blank node with random id
\&
\&  ### How to retrieve RDF
\&
\&  $x\->rel(\*(Aqfoaf:knows\*(Aq);    # retrieve a person that $x knows
\&  $x\->rev(\*(Aqfoaf:knows\*(Aq);    # retrieve a person known by $x
\&
\&  $x\->rels(\*(Aqfoaf:knows\*(Aq);   # retrieve all people that $x knows
\&  $x\->revs(\*(Aqfoaf:knows\*(Aq);   # retrieve all people known by $x
\&
\&  $x\->foaf_knows;           # short form of $x\->rel(\*(Aqfoaf:knows\*(Aq)
\&  $x\->foaf_knows_;          # short form of $x\->rels(\*(Aqfoaf:knows\*(Aq)
\&
\&  $x\->rels;                 # array reference with a list of properties
\&  $x\->revs;                 # same as rels, but other direction
\&
\&  $x\->type;                 # same as $x\->rel(\*(Aqrdf:type\*(Aq)
\&  $x\->types;                # same as $x\->rels(\*(Aqrdf:type\*(Aq)
\&
\&  $g\->subjects( \*(Aqrdf:type\*(Aq, \*(Aqfoaf:Person\*(Aq );  # retrieve subjects
\&  $g\->predicates( $subject, $object );        # list predicates
\&  $g\->objects( $subject, \*(Aqfoaf:knows\*(Aq );      # list objects
\&
\&  ### How to add RDF
\&
\&  $g\->add( $rdfdata, format => \*(Aqrdfxml\*(Aq );    # parse and add
\&  $g\->add( $subject, $predicate, $object );   # add single triple
\&
\&  ### How to show RDF
\&
\&  $g\->turtle;  # dump in RDF/Turtle syntax
\&  $g\->ttlpre;  # dump in RDF/Turtle, wrapped in a HTML <pre> tag
\&  $g\->rdfxml;  # dump in RDF/XML
\&  $g\->rdfjson; # dump in RDF/JSON
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This module wraps RDF::Trine::Node to provide simple node-centric access to
\&\s-1RDF\s0 data. It was designed to access \s-1RDF\s0 within Template Toolkit but the
module does not depend on or and can be used independently. Basically, an
instance of RDF::Lazy contains an unlabeled \s-1RDF\s0 graph and a set of namespace
prefixes. For lazy access and graph traversal, each \s-1RDF\s0 node
(RDF::Lazy::Node) is tied to the graph.
.SH "METHODS"
.IX Header "METHODS"
.ie n .SS "cache( [ $cache ] )"
.el .SS "cache( [ \f(CW$cache\fP ] )"
.IX Subsection "cache( [ $cache ] )"
Get and/or set a cache for loading \s-1RDF\s0 from URIs or URLs. A \f(CW$cache\fR can be
any blessed object that supports method \f(CW\*(C`get($uri)\*(C'\fR and \f(CW\*(C`set($uri,$value)\*(C'\fR.
For instance one can enable a simple file cache with \s-1CHI\s0 like this:
.PP
.Vb 6
\&    my $rdf = RDF::Lazy\->new(
\&        cache => CHI\->new(
\&            driver => \*(AqFile\*(Aq, root_dir => \*(Aq/tmp/cache\*(Aq,
\&            expires_in => \*(Aq1 day\*(Aq
\&        )
\&    );
.Ve
.PP
By default, \s-1RDF\s0 is stored in Turtle syntax for easy inspection.
.ie n .SS "load( $uri )"
.el .SS "load( \f(CW$uri\fP )"
.IX Subsection "load( $uri )"
Load \s-1RDF\s0 from an \s-1URI\s0 or \s-1URL. RDF\s0 data is optionally retrieved from a cache.
Returns the number of triples that have been added (which could be zero if
all loaded triples are duplicates).
.ie n .SS "new ( [ [ rdf => ] $rdf ] [, namespaces => $namespaces ] [ %options ])"
.el .SS "new ( [ [ rdf => ] \f(CW$rdf\fP ] [, namespaces => \f(CW$namespaces\fP ] [ \f(CW%options\fP ])"
.IX Subsection "new ( [ [ rdf => ] $rdf ] [, namespaces => $namespaces ] [ %options ])"
Return new \s-1RDF\s0 graph. Namespaces can be provided as hash reference or as
RDF::Trine::NamespaceMap or \s-1RDF::NS\s0. By default, the current local
version of \s-1RDF::NS\s0 is used.  \s-1RDF\s0 data can be <RDF:Trine::Model> or
RDF::Trine::Store, which are used by reference, or many other forms, as
supported by add.
.ie n .SS "resource ( $uri )"
.el .SS "resource ( \f(CW$uri\fP )"
.IX Subsection "resource ( $uri )"
Return RDF::Lazy::Resource node. The following statements are equivalent:
.PP
.Vb 2
\&    $graph\->resource(\*(Aqhttp://example.org\*(Aq);
\&    $graph\->uri(\*(Aq<http://example.org>\*(Aq);
.Ve
.ie n .SS "literal ( $string , $language_or_datatype, $datatype )"
.el .SS "literal ( \f(CW$string\fP , \f(CW$language_or_datatype\fP, \f(CW$datatype\fP )"
.IX Subsection "literal ( $string , $language_or_datatype, $datatype )"
Return RDF::Lazy::Literal node.
.ie n .SS "blank ( [ $identifier ] )"
.el .SS "blank ( [ \f(CW$identifier\fP ] )"
.IX Subsection "blank ( [ $identifier ] )"
Return RDF::Lazy::Blank node. A random identifier is generated unless you
provide an identifier as parameter.
.ie n .SS "uri ( $name | $node )"
.el .SS "uri ( \f(CW$name\fP | \f(CW$node\fP )"
.IX Subsection "uri ( $name | $node )"
Returns a node that is connected to the graph. Note that every valid \s-1RDF\s0 node
is part of any \s-1RDF\s0 graph: this method does not check whether the graph actually
contains a triple with the given node. You can either pass a name or an
instance of RDF::Trine::Node. This method is also called for any undefined
method, so the following statements are equivalent:
.PP
.Vb 2
\&    $graph\->true;
\&    $graph\->uri(\*(Aqtrue\*(Aq);
.Ve
.SS "rel / rels / rev / revs"
.IX Subsection "rel / rels / rev / revs"
Can be used to traverse the graph. See RDF::Lazy::Node:
.PP
.Vb 2
\&    $node\->rel( ... )           # where $node is located in $graph
\&    $graph\->rel( $node, ... )   # equivalent
.Ve
.SS "add"
.IX Subsection "add"
Add \s-1RDF\s0 data. \fISorry, not documented yet!\fR
.ie n .SS "ttl ( [ $node ] )"
.el .SS "ttl ( [ \f(CW$node\fP ] )"
.IX Subsection "ttl ( [ $node ] )"
Returns a RDF/Turtle representation of a node's bounded description.
.ie n .SS "ttlpre ( [ $node ] )"
.el .SS "ttlpre ( [ \f(CW$node\fP ] )"
.IX Subsection "ttlpre ( [ $node ] )"
Returns an \s-1HTML\s0 escaped RDF/Turtle representation of a node's bounded
description, wrapped in a \s-1HTML\s0 \f(CW\*(C`<pre class="turtle">\*(C'\fR element.
.ie n .SS "ns ( $prefix | $namespace | $prefix => $namespace )"
.el .SS "ns ( \f(CW$prefix\fP | \f(CW$namespace\fP | \f(CW$prefix\fP => \f(CW$namespace\fP )"
.IX Subsection "ns ( $prefix | $namespace | $prefix => $namespace )"
Gets or sets a namespace mapping for the entire graph. By default, RDF::Lazy
makes use of popular namespaces defined in \s-1RDF::NS\s0.
.PP
.Vb 3
\&   $g\->ns(\*(Aqdc\*(Aq);   # returns \*(Aqhttp://purl.org/dc/elements/1.1/\*(Aq
\&   $g\->ns(\*(Aqhttp://purl.org/dc/elements/1.1/\*(Aq);  # returns \*(Aqdc\*(Aq
\&   $g\->ns( dc => \*(Aqhttp://example.org/\*(Aq );       # modify mapping
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
RDF::Helper and RDF::TrineShortcuts provide similar APIs. Another similar framework
for \s-1PHP\s0 and Python is Graphite: http://graphite.ecs.soton.ac.uk/,
http://code.google.com/p/python\-graphite/.
.SH "AUTHOR"
.IX Header "AUTHOR"
Jakob Vo\*8 <voss@gbv.de>
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
This software is copyright (c) 2013 by Jakob Vo\*8.
.PP
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.