Github user jessehatfield commented on a diff in the pull request:
https://github.com/apache/incubator-rya/pull/209#discussion_r134620096
--- Diff:
sail/src/main/java/org/apache/rya/rdftriplestore/inference/HasSelfVisitor.java
---
@@ -0,0 +1,81 @@
+package org.apache.rya.rdftriplestore.inference;
+
+import org.apache.rya.api.RdfCloudTripleStoreConfiguration;
+import org.openrdf.model.Resource;
+import org.openrdf.model.URI;
+import org.openrdf.model.vocabulary.RDF;
+import org.openrdf.query.algebra.Extension;
+import org.openrdf.query.algebra.ExtensionElem;
+import org.openrdf.query.algebra.StatementPattern;
+import org.openrdf.query.algebra.Var;
+
+/**
+ * Expands the query tree to account for any relevant has-self class
expressions
+ * in the ontology known to the {@link InferenceEngine}.
+ *
+ * Only operates on {@link StatementPattern} nodes, and only those
including a
+ * defined type or defined predicate which is relevant to a has-self
expression
+ * in the ontology. When applicable, replaces the node with one or more
+ * {@link InferUnion}s, one of whose leaves is the original
StatementPattern.
+ *
+ * A has-self restriction defines the set of resources that are connected
to
+ * themselves by a property. If the ontology states that a type is a
resource
+ * that has a self referencing property, then the inference engine should:
+ * <li>1. Rewrite queries of the from ?x rdf:type :T to find all resources
+ * matching ?x :P ?x (as well as anything explicitly stated to be of type
:T)
+ * </li>
+ * <li>2. Rewrite queries of the from :CONST :P ?o or ?subj :P :CONST to
match
+ * :CONST if :CONST is known to have the type :T
+ * </li>
+ */
+public class HasSelfVisitor extends AbstractInferVisitor {
+ private static final Var TYPE_VAR = new Var("p", RDF.TYPE);
+
+ /**
+ * Creates a new {@link HasSelfVisitor}, which is enabled by default.
+ * @param conf The {@link RdfCloudTripleStoreConfiguration}.
+ * @param inferenceEngine The InferenceEngine containing the relevant
ontology.
+ */
+ public HasSelfVisitor(final RdfCloudTripleStoreConfiguration conf,
final InferenceEngine inferenceEngine) {
+ super(conf, inferenceEngine);
+ include = conf.hasSelf();
+ }
+
+ @Override
+ protected void meetSP(final StatementPattern node) throws Exception {
+ final URI pred = (URI) node.getPredicateVar().getValue();
+ final Var obj = node.getObjectVar();
+ //if originalSP like (?s rdf:type :C1): require that C1 is
defined, i.e. not a variable
+ // node <- originalSP
+ final StatementPattern clone = node.clone();
+ if(pred.equals(RDF.TYPE) && obj.isConstant()) {
+ //for property in getHasSelfImplyingType(C1):
+ for (final URI property :
inferenceEngine.getHasSelfImplyingType((URI) obj.getValue())) {
+ //node <- InferUnion(node, StatementPattern(?s, property,
?s)).
+ final InferUnion union = new InferUnion(clone, new
StatementPattern(clone.getSubjectVar(), new Var("p", property),
clone.getSubjectVar()));
--- End diff --
Similar comment to TYPE_VAR, might rename from "p" to something like the
property's actual URI.
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