1Attean::API::Model(3) User Contributed Perl DocumentationAttean::API::Model(3)
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6 Attean::API::Model - RDF Model
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9 This document describes Attean::API::Model version 0.030
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12 The Attean::API::Model role defines a common API for all RDF models to
13 conform to. It is provides a consistent interface for probing,
14 counting, and retrieving Attean::API::Quads matching a pattern, as well
15 as related functionality such as enumerating the graph names, and
16 extracting structured data from the models' quads.
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19 The following methods are required by the Attean::API::Model role:
20 "get_quads( $subject, $predicate, $object, $graph )"
22 Returns an Attean::API::Iterator for quads in the model that match
23 the supplied $subject, $predicate, $object, and $graph.
24 Any of these terms may be:
26 * An Attean::API::Term object, in which case matching is equality-
28 based
29 * A Attean::API::Variable object or "undef", in which case that
31 term will be considered as a wildcard for the purposes of matching
32 * An ARRAY reference of Attean::API::Term objects, in which case
34 the matching will be equality-based on the disjunction of the
35 supplied terms
36 The returned iterator conforms to both Attean::API::Iterator and
38 Attean::API::QuadIterator.
39 "count_quads( $subject, $predicate, $object, $graph )"
41 Returns the number of quads in the model matching the supplied
42 pattern (using the same matching semantics as "get_quads").
43 "count_quads_estimate( $subject, $predicate, $object, $graph )"
45 Returns an estimate of the number of quads in the model matching
46 the supplied pattern (using the same matching semantics as
47 "get_quads"). This estimate is guaranteed to non-zero if the count
48 returned from an equivalent call to `count_quads` would return a
49 non-zero result.
50 "get_graphs"
52 Returns an Attean::API::Iterator of distinct Attean::API::Term
53 objects that are used in the graph position of quads in the model.
54
56 The Attean::API::Model role provides default implementations of the
57 following methods:
58 "get_bindings( $subject, $predicate, $object, $graph )"
60 Returns an Attean::API::Iterator of Attean::API::Result objects
61 corresponding to quads in the model matching the supplied pattern.
62 For each Attean::API::Variable in the pattern list, a mapping will
63 be present in the corresponding result object. For example,
64 "$model->get_bindings( variable('s') )" will return an iterator of
65 results containing just a mapping from 's' to subjects of all quads
66 in the model.
67 "get_list( $graph, $head )"
69 Returns an Attean::API::Iterator of Attean::API::Term objects that
70 are members of the rdf:List with the specified $head (and matching
71 restricted to only the specified $graph).
72 To check if a certain term is a list, the "holds" method may be
74 used, for example:
75 $model->holds($head, iri('http://www.w3.org/1999/02/22-rdf-syntax-ns#first'), undef, $graph))
77 will return true if a given term $head is a list.
79 "get_sequence( $graph, $head )"
81 Returns an Attean::API::Iterator of Attean::API::Term objects that
82 are members of the rdf:Sequence with the specified $head (and
83 matching restricted to only the specified $graph).
84 "subjects( $predicate, $object, $graph )"
86 Returns an Attean::API::Iterator of Attean::API::Term objects of
87 all subjects of quads matching the supplied pattern (using the same
88 matching semantics as "get_quads").
89 The objects returned will not necessarily be unique. It will
91 instead be equivalent to calling "get_quads" and accessing
92 "$quad->subject" for each $quad value returned by the iterator. For
93 an iterator of unique subjects, use "$model->subjects->uniq".
94 "predicates( $subject, $object, $graph )"
96 Returns an Attean::API::Iterator of Attean::API::Term objects of
97 all predicates of quads matching the supplied pattern (using the
98 same matching semantics as "get_quads" with an "undef" predicate).
99 The objects returned will not necessarily be unique (see the note
101 for "subjects" above).
102 "objects( $subject, $predicate, $graph )"
104 Returns an Attean::API::Iterator of Attean::API::Term objects of
105 all objects of quads matching the supplied pattern (using the same
106 matching semantics as "get_quads" with an "undef" object).
107 The objects returned will not necessarily be unique (see the note
109 for "subjects" above).
110 "graphs( $subject, $predicate, $object )"
112 Returns an Attean::API::Iterator of Attean::API::Term objects of
113 all graphs of quads matching the supplied pattern (using the same
114 matching semantics as "get_quads" with an "undef" graph).
115 The objects returned will not necessarily be unique (see the note
117 for "subjects" above).
118 "graph_nodes( $graph )"
120 Returns an Attean::API::Iterator of Attean::API::Term objects of
121 unique subjects and objects present in the specified $graph.
122 "holds($s, $p, $o, $g)"
124 "holds($triple_pattern)"
125 "holds($quad_pattern)"
126 Returns true if the triple/quad pattern matches any data in the
127 model, false otherwise.
128 "algebra_holds($algebra, $graph)"
130 "algebra_holds($algebra, \@graphs)"
131 Returns true if the algebra, evaluated with the supplied default
132 graph(s) matches any data in the model, false otherwise. This is
133 equivalent to the result of an ASK query over the supplied algebra.
134 "evaluate($algebra, [ $default_graph | \@default_graphs ])"
136 Returns an Attean::API::Iterator of Attean::Result objects which
137 result from evaluating the given query algebra (e.g. one obtained
138 from parsing a query with AtteanX::Parser::SPARQL) with the
139 supplied default graph(s) against data in the model.
140
142 Please report any bugs or feature requests to through the GitHub web
143 interface at <https://github.com/kasei/attean/issues>.
144
147 Gregory Todd Williams "<gwilliams@cpan.org>"
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150 Copyright (c) 2014--2020 Gregory Todd Williams. This program is free
151 software; you can redistribute it and/or modify it under the same terms
152 as Perl itself.
153perl v5.32.1 2021-02-08 Attean::API::Model(3)