Overview

NAME
    RDF::TrineShortcuts - totally unauthorised module for cheats and
    charlatans

SYNOPSIS
      use RDF::TrineShortcuts;
  
      my $model = rdf_parse('http://example.com/data.rdf');
      my $query = 'ASK { ?person a <http://xmlns.com/foaf/0.1/Person> . }';
      if (rdf_query($query, $model))
      {
        print "Document describes a person.\n";
      }
      else
      {
        print "Document doesn't describe a person.\n";
        print "What does it describe? Let's see...\n";
        print rdf_string($model);
      }

DESCRIPTION
    This module exports three functions which simplify frequently performed
    tasks using RDF::Trine and RDF::Query. (A number of other functions are
    also available but not exported by default.)

    *   "rdf_parse($data)"

    *   "rdf_string($model, $format)"

    *   "rdf_query($sparql, $endpoint_or_model)"

    In addition, because it calls "use RDF::Trine", "use RDF::Query", and
    "use RDF::Query::Client", your code doesn't need to.

  Main Functions
    "rdf_parse($data)"
        $data can be some serialised RDF (in RDF/XML, Turtle, RDF/JSON, or
        any other format that RDF::Trine::Parser supports); or a URI (string
        or URI object); or an HTTP::Message object; or a hashref (as per
        RDF::Trine::Model's add_hashref method); or a file name or an open
        file handle; or an RDF::Trine::Iterator::Graph. Essentially it could
        be anything you could reasonably expect to grab RDF from. It can be
        undef.

        If $input is a blessed object that rdf_parse is unable to natively
        deal with, it will attempt to call "$input->TO_RDF" and deal with
        the result instead. (This is similar in spirit to the JSON module's
        convert_blessed functionality.)

        The function returns an RDF::Trine::Model.

        There are additional optional named arguments, of which the two most
        useful are probably 'base', which sets the base URI for any relative
        URI references; and 'type', which indicates the media type of the
        input (though the function can usually guess this quite reliably).

          $model = rdf_parse($input,
                             'base' => 'http://example.com/',
                             'type' => 'application/rdf+xml');

        Other named arguments include 'model' to provide an existing
        RDF::Trine::Model to add statements to; and 'context' for providing
        a context/graph URI (which may be a string, URI object or
        RDF::Trine::Node).

    "rdf_string($model, $format)"
        Serialises an RDF::Trine::Model to a string.

        $model is the model to serialise. If $model is not an
        RDF::Trine::Model object, then it's automatically passed through
        rdf_parse first.

        $format is the format to use. One of 'RDFXML' (the default),
        'RDFJSON', 'Turtle', 'Canonical NTriples' or 'NTriples'. If $format
        is not one of the above, then the function will try to guess what
        you meant.

        Preferred namespace names can be provided as a named argument:

         print rdf_string($model, 'turtle',
            namespaces => { foo=>'http://example.com/vocabs/foo#' });

        You can find the relevant Internet media type like this:

         my $type;
         my $string = rdf_string($model, 'rdfxml', media_type=>\$type);
         print $cgi->header($type), $string and exit;

    "rdf_query($sparql, $endpoint)"
        $sparql is a SPARQL query to be run at $endpoint.

        $endpoint may be either an endpoint URI (string or URI object) or a
        model supported by RDF::Query (e.g. an RDF::Trine::Model.)

        Query languages other than SPARQL may be used (see <RDF::Query> for
        a list of supported languages). e.g.

          rdf_query("SELECT ?s, ?p, ?o WHERE (?s, ?p, ?o)"
                    $model,
                    query_lang=>'rdql');

        Options query_base, query_update and query_load_data correspond to
        the base, update and load_data options passed to RDF::Query's
        constructor.

        If the SPARQL query returns a boolean (i.e. an ASK query), then this
        function returns a boolean. If the query returns a graph (i.e.
        CONSTRUCT or DESCRIBE), then this function returns an
        RDF::Trine::Model corresponding to the graph. Otherwise (i.e.
        SELECT) it returns an RDF::Trine::Iterator object.

        For queries which return a graph, an optional $model parameter can
        be passed containing an existing RDF::Trine::Model to add statements
        to:

          rdf_query("CONSTRUCT {?s ?p ?o} WHERE {?s ?p ?o}",
                    'http://example.com/sparql',
                    model => $model);

        This function can expand a small set of commonly used prefixes. For
        example:

         $result = rdf_query('SELECT ?id ?name {?id foaf:name ?name}',
                             $model);

        The hashref $RDF::TrineShortcuts::Namespaces is consulted for
        expansions.

  Additional Functions
    These are not exported by default, so need to be imported explicitly,
    e.g.

     use RDF::TrineShortcuts qw(:default rdf_node rdf_statement);

    "rdf_node($value, %args)"
        Creates an RDF::Trine::Node object.

        Will attempt to automatically determine whether $value is a blank
        node, resource, literal or variable, but an optional named argument
        'type' can be used to explicitly indicate this.

        For literals, named arguments 'datatype' and 'lang' are allowed. If
        'datatype' is not a URI, then it's assumed to be an XSD datatype.

         $node = rdf_node("Hello", type=>'literal', lang=>'en');

        For resources, the named argument 'base' is allowed.

        If $value is undef, then it would normally be treated like a
        zero-length string. By setting the argument 'passthrough_undef' to
        1, you can allow it to pass thorugh and return undef.

        This function can expand a small set of commonly used prefixes. For
        example:

         $node = rdf_node('foaf:primaryTopic');

        The hashref $RDF::TrineShortcuts::Namespaces is consulted for
        expansions.

        This function is not exported by default, but can be exported using
        the tag ':nodes' or ':all'.

         use RDF::TrineShortcuts qw(:default :nodes);

    "rdf_literal($value, %args)", "rdf_blank($value, %args)",
    "rdf_resource($value, %args)", "rdf_variable($value, %args)"
        Shortcuts for rdf_node($value, type=>'literal', %args) and so on.
        The rdf_resource function will create a blank node resource if
        $value begins '_:'.

        These functions are not exported by default, but can be exported
        using the tag ':nodes' or ':all'.

         use RDF::TrineShortcuts qw(:all);

    "rdf_statement($s, $p, $o, [$g])", "rdf_statement($ntriple, [$g])"
        Returns an RDF::Trine::Statement. Parameters $s, $p, $o and $g can
        each be either a plain string that could be passed to rdf_node, or
        an arrayref of rdf_node parameters, or an RDF::Trine::Node.

        $ntriple is a single N-Triples statement.

        This function is not exported by default, but can be exported using
        the tag ':all'.

         use RDF::TrineShortcuts qw(:all);

    "flatten_node($node)"
        Converts a node back to a string.

        By default, blank nodes and variables are stringified to their
        N-Triples and SPARQL representations; URIs are stringified without
        angled bracket delimiters; and literals to their literal values.

        Various options are available: 'resource_as', 'blank_as',
        'variable_as' and 'literal_as' can each be set to 'ntriples',
        'value' or 'default'.

         print flatten_node($my_resource, resource_as=>'ntriples');

        This function is not exported by default, but can be exported using
        the tag ':flatten' or ':all'.

         use RDF::TrineShortcuts qw(:default :flatten);

    "flatten_iterator($iter)"
        Converts an iterator to a Perl list. In list context returns a list;
        in scalar context returns an arrayref instead.

        Each item in the list is, in the case of a bindings iterator, a
        hashref; or, in the case of a triple/quad iterator, an arrayref [s,
        p, o, g]. For boolean iterators, $iter->get_boolean is returned. The
        nodes which are values in the hashref/arrayref are flattened with
        flatten_node, unless flatten_iterator is called with
        'keep_nodes'=>1.

          my @results = flatten_iterator($iter, keep_nodes=>1);

        You can pass additional options for flatten_node too:

          my @results = flatten_iterator($iter, resource_as=>'ntriples');

        This function is not exported by default, but can be exported using
        the tag ':flatten' or ':all'.

         use RDF::TrineShortcuts qw(:default :flatten);

  Object-Oriented Interface
    RDF::TrineShortcuts has an alternative, object-oriented interface, not
    enabled by default.

     use RDF::TrineShortcuts -methods;
 
     my $model = RDF::Trine::Model->temporary_model;
 
     # Alias for rdf_parse($some_turtle, model=>$model) 
     $model->parse($some_turtle);
 
     # Alias for rdf_string($model, 'rdfxml');
     my $rdfxml = $model->parse('rdfxml');
     print $rdfxml;
 
     my $query = 'SELECT ?name WHERE { ?id foaf:name ?name . } ';
 
     # Alias for rdf_query($query, $model);
     my $result = $model->sparql($query);
 
     # Alias for flatten_iterator();
     my @result = $result->flatten;

    And so on. The following methods are set up:

    *   RDF::Trine::Model: "parse", "string", "sparql".

    *   RDF::Trine::Node: "flatten".

    *   RDF::Trine::Iterator: "flatten".

    *   URI::http: "sparql".

    *   URI: "resource".

    Future versions of the RDF::Trine and URI packages may break this. It's
    a pretty dodgy feature.

    You can load the normal RDF::TrineShortcuts function-based interface in
    addition to the object-oriented interface like this:

     use RDF::TrineShortcuts qw(:default -methods);

    Or everything:

     use RDF::TrineShortcuts qw(:all -methods);

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

SEE ALSO
    RDF::Trine, RDF::Query, RDF::Query::Client.

    <http://www.perlrdf.org/>.

    This module is distributed with three command-line RDF tools. trapper is
    an RDF fetcher/parser/serialiser; toquet is a SPARQL query tool; trist
    is an RDF statistics tool.

AUTHOR
    Toby Inkster <tobyink@cpan.org>.

COPYRIGHT
    Copyright 2010 Toby Inkster

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