Github user jessehatfield commented on a diff in the pull request:
https://github.com/apache/incubator-rya/pull/180#discussion_r132230928
--- Diff:
sail/src/main/java/org/apache/rya/rdftriplestore/inference/InferenceEngine.java
---
@@ -142,6 +143,53 @@ public void refreshGraph() throws
InferenceEngineException {
}
}
+ // Add unions to the subclass graph: if c owl:unionOf LIST(c1,
c2, ... cn), then any
+ // instances of c1, c2, ... or cn are also instances of c,
meaning c is a superclass
+ // of all the rest.
+ // (In principle, an instance of c is likewise implied to be
at least one of the other
+ // types, but this fact is ignored for now to avoid
nondeterministic reasoning.)
+ iter = RyaDAOHelper.query(ryaDAO, null, OWL.UNIONOF, null,
conf);
+ try {
+ while (iter.hasNext()) {
+ Statement st = iter.next();
+ Value unionType = st.getSubject();
+ // Traverse the list of types constituting the union
+ Value current = st.getObject();
+ while (current instanceof Resource &&
!RDF.NIL.equals(current)) {
+ Resource listNode = (Resource) current;
+ CloseableIteration<Statement,
QueryEvaluationException> listIter = RyaDAOHelper.query(ryaDAO,
+ listNode, RDF.FIRST, null, conf);
+ try {
+ if (listIter.hasNext()) {
+ Statement firstStatement = listIter.next();
+ if (firstStatement.getObject() instanceof
Resource) {
+ Resource subclass = (Resource)
firstStatement.getObject();
+ Statement subclassStatement =
vf.createStatement(subclass, RDFS.SUBCLASSOF, unionType);
+ addStatementEdge(graph,
RDFS.SUBCLASSOF.stringValue(), subclassStatement);
+ }
+ }
+ } finally {
+ listIter.close();
+ }
+ listIter = RyaDAOHelper.query(ryaDAO, listNode,
RDF.REST, null, conf);
+ try {
+ if (listIter.hasNext()) {
+ current = listIter.next().getObject();
--- End diff --
Yep, a union is given as a linked list so we just walk down adding subclass
statements until we get to a node with no rdf:rest or with rdf:rest equal to
rdf:nil. If the list is poorly-formed or someone tries to express the union
using the wrong collection type ([describes unionOf
expression](https://www.w3.org/TR/owl2-rdf-based-semantics/#Semantic_Conditions_for_Boolean_Connectives)
| [gives interpretation of
sequence](https://www.w3.org/TR/owl2-rdf-based-semantics/#Semantic_Conditions))
then it won't work. In most cases that just means the intended union isn't
fully represented, but I suppose if it were somehow a cyclical list, we'd end
up in an infinite loop.
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