GH-1720: Filter out literals-as-subjects from --rdfs

jena-arq/src/main/java/org/apache/jena/rdfs/RDFSFactory.java

@@ -22,6 +22,7 @@
 import org.apache.jena.query.DatasetFactory;
 import org.apache.jena.riot.system.StreamRDF;
 import org.apache.jena.sparql.core.DatasetGraph;
+import org.apache.jena.sparql.util.NodeUtils;
 
 /** Factory for data+RDFS inference. */
 public class RDFSFactory {
@@ -79,4 +80,9 @@ public static StreamRDF streamRDFS(StreamRDF data, Graph vocab) {
     public static StreamRDF streamRDFS(StreamRDF data, SetupRDFS setup) {
         return new InfStreamRDFS(data, setup);
     }
+
+    /** RDFS can generate "symmetric RDF", "generalized RDF" - e.g. triples with literals as subjects. */
+    public static StreamRDF removeGeneralizedRDF(StreamRDF data) {
+        return NodeUtils.removeGeneralizedRDF(data);
+    }
 }

jena-arq/src/main/java/org/apache/jena/rdfs/SetupRDFS.java

@@ -24,14 +24,6 @@
 /** RDFS setup in Node space */
 public class SetupRDFS extends BaseSetupRDFS<Node> {
 
-    /**
-     * {@code incDerivedDataRDFS} causes the engine to look for RDFS relationships in the data
-     * as if TBox (rules) and ABox (ground data) are one unit.
-     * <p>
-     * Set true if abox == tbox.
-     * <p>
-     * Can choose false or true if abox != tbox.
-     */
     public SetupRDFS(Graph vocab) {
         super(vocab);
     }

jena-arq/src/main/java/org/apache/jena/riot/system/StreamRDF2.java

@@ -21,8 +21,8 @@
 import org.apache.jena.graph.Triple ;
 import org.apache.jena.sparql.core.Quad ;
 
-/** Send to two stream */
-public class StreamRDF2 implements StreamRDF 
+/** Send to two streams */
+public class StreamRDF2 implements StreamRDF
 {
     protected final StreamRDF sink1 ;
     protected final StreamRDF sink2 ;
@@ -31,7 +31,7 @@ public StreamRDF2(StreamRDF sink1, StreamRDF sink2) {
         this.sink1 = sink1 ;
         this.sink2 = sink2 ;
     }
-    
+
     @Override
     public void start() {
         sink1.start() ;

jena-arq/src/main/java/org/apache/jena/sparql/modify/TemplateLib.java

@@ -30,7 +30,7 @@
 import org.apache.jena.sparql.core.Substitute;
 import org.apache.jena.sparql.core.Var;
 import org.apache.jena.sparql.engine.binding.Binding;
-import org.apache.jena.sparql.util.ModelUtils;
+import org.apache.jena.sparql.util.NodeUtils;
 
 public class TemplateLib {
     // See also Substitute -- combine?
@@ -79,7 +79,7 @@ public Iterator<Triple> apply(final Binding b) {
                 List<Triple> tripleList = new ArrayList<>(triples.size());
                 for ( Triple triple : triples ) {
                     Triple q = subst(triple, b, bNodeMap);
-                    if ( !q.isConcrete() || !ModelUtils.isValidAsStatement(q.getSubject(), q.getPredicate(), q.getObject()) ) {
+                    if ( !q.isConcrete() || ! NodeUtils.isValidAsRDF(q.getSubject(), q.getPredicate(), q.getObject()) ) {
                         // Log.warn(TemplateLib.class, "Unbound quad:
                         // "+FmtUtils.stringForQuad(quad)) ;
                         continue;

jena-arq/src/main/java/org/apache/jena/sparql/util/ModelUtils.java

@@ -18,22 +18,22 @@
 
 package org.apache.jena.sparql.util;
 
-import java.util.Iterator ;
-
-import org.apache.jena.atlas.iterator.Iter ;
-import org.apache.jena.graph.Node ;
-import org.apache.jena.graph.Triple ;
-import org.apache.jena.query.QueryException ;
-import org.apache.jena.rdf.model.Model ;
-import org.apache.jena.rdf.model.RDFNode ;
-import org.apache.jena.rdf.model.Statement ;
-import org.apache.jena.rdf.model.StmtIterator ;
-import org.apache.jena.rdf.model.impl.LiteralImpl ;
-import org.apache.jena.rdf.model.impl.ResourceImpl ;
-import org.apache.jena.rdf.model.impl.StmtIteratorImpl ;
-import org.apache.jena.sparql.ARQInternalErrorException ;
+import java.util.Iterator;
+
+import org.apache.jena.atlas.iterator.Iter;
+import org.apache.jena.graph.Node;
+import org.apache.jena.graph.Triple;
+import org.apache.jena.query.QueryException;
+import org.apache.jena.rdf.model.Model;
+import org.apache.jena.rdf.model.RDFNode;
+import org.apache.jena.rdf.model.Statement;
+import org.apache.jena.rdf.model.StmtIterator;
+import org.apache.jena.rdf.model.impl.LiteralImpl;
+import org.apache.jena.rdf.model.impl.ResourceImpl;
+import org.apache.jena.rdf.model.impl.StmtIteratorImpl;
+import org.apache.jena.sparql.ARQInternalErrorException;
 import org.apache.jena.util.ModelCollector;
-import org.apache.jena.util.iterator.ClosableIterator ;
+import org.apache.jena.util.iterator.ClosableIterator;
 
 public class ModelUtils
 {
@@ -46,22 +46,22 @@ public class ModelUtils
 
     public static RDFNode convertGraphNodeToRDFNode(Node node, Model model) {
         if ( node.isVariable() )
-            throw new QueryException("Variable: "+node) ;
+            throw new QueryException("Variable: "+node);
 
         // Best way.
         if ( model != null )
-             return model.asRDFNode(node) ;
+             return model.asRDFNode(node);
 
         if ( node.isLiteral() )
-            return new LiteralImpl(node, null) ;
+            return new LiteralImpl(node, null);
 
         if ( node.isURI() || node.isBlank() )
-            return new ResourceImpl(node, null) ;
+            return new ResourceImpl(node, null);
 
         if ( node.isNodeTriple() )
-            return new ResourceImpl(node, null) ;
+            return new ResourceImpl(node, null);
 
-        throw new ARQInternalErrorException("Unknown node type for node: "+node) ;
+        throw new ARQInternalErrorException("Unknown node type for node: "+node);
     }
 
     /** Convert a {@link Node} (graph SPI) to an RDFNode (model API)
@@ -73,18 +73,17 @@ public static RDFNode convertGraphNodeToRDFNode(Node node) {
         return convertGraphNodeToRDFNode(node, null);
     }
 
-    public static Statement tripleToStatement(Model model, Triple t)
-    {
+    public static Statement tripleToStatement(Model model, Triple t) {
         if ( model == null )
-            throw new ARQInternalErrorException("Attempt to create statement with null model") ;
+            throw new ARQInternalErrorException("Attempt to create statement with null model");
 
-        Node sNode = t.getSubject() ;
-        Node pNode = t.getPredicate() ;
-        Node oNode = t.getObject() ;
+        Node sNode = t.getSubject();
+        Node pNode = t.getPredicate();
+        Node oNode = t.getObject();
 
         if (!isValidAsStatement(sNode, pNode, oNode)) return null;
 
-        return model.asStatement(t) ;
+        return model.asStatement(t);
     }
 
     /**
@@ -97,19 +96,12 @@ public static Statement tripleToStatement(Model model, Triple t)
      * @param p Predicate
      * @param o Object
      * @return True if a valid Statement can be formed
+     *
+     * @deprecated Use {@link NodeUtils#isValidAsRDF(Node, Node, Node)}.
      */
-    public static boolean isValidAsStatement(Node s, Node p, Node o)
-    {
-        if ( s.isLiteral() || s.isVariable() )
-            return false ;
-
-        if ( ! p.isURI() )  // Not variable, literal or blank.
-            return false ;
-
-        if ( o.isVariable() )
-            return false ;
-
-        return true;
+    @Deprecated
+    public static boolean isValidAsStatement(Node s, Node p, Node o) {
+        return NodeUtils.isValidAsRDF(s, p, o);
     }
 
     public static StmtIterator triplesToStatements(final Iterator<Triple> it, final Model refModel) {

jena-arq/src/main/java/org/apache/jena/sparql/util/NodeUtils.java

@@ -25,7 +25,11 @@
 import org.apache.jena.datatypes.xsd.XSDDatatype ;
 import org.apache.jena.graph.Node ;
 import org.apache.jena.graph.NodeFactory ;
+import org.apache.jena.graph.Triple;
 import org.apache.jena.rdf.model.impl.Util;
+import org.apache.jena.riot.system.StreamRDF;
+import org.apache.jena.riot.system.StreamRDFWrapper;
+import org.apache.jena.sparql.core.Quad;
 import org.apache.jena.sparql.expr.ExprEvalException ;
 import org.apache.jena.sparql.expr.NodeValue ;
 import org.apache.jena.sparql.expr.nodevalue.NodeFunctions ;
@@ -184,4 +188,66 @@ public static boolean isXSDNumeric(Node node) {
      */
     public static boolean isLangString(Node n) { return Util.isLangString(n) ; }
 
+    /**
+     * Determines whether a triple (as s/p/o) is valid as a RDF statement.
+     * <p>
+     * This function reflects the fact that the {@link Triple} API is flexible in
+     * allowing any Node type in any position (including non-RDF node types like
+     * Variable) and as such not all Triples can be safely converted into Statements
+     * </p>
+     * @param s Subject
+     * @param p Predicate
+     * @param o Object
+     * @return True if a valid as a statement
+     */
+    public static boolean isValidAsRDF(Node s, Node p, Node o) {
+        if ( s == null || ( ! s.isBlank() && ! s.isURI() ) )
+            return false;
+        if ( p == null || ( ! p.isURI() ) )
+            return false;
+        if ( o == null || ( ! o.isBlank() && ! o.isURI() && ! o.isLiteral() && !o.isNodeTriple() ) )
+            return false;
+        return true;
+    }
+
+    /**
+     * Determines whether a quad (as g/s/p/o) is valid as a RDF statement.
+     * <p>
+     * This function reflects the fact that the {@link Triple} API is flexible in
+     * allowing any Node type in any position (including non-RDF node types like
+     * Variable) and as such not all Triples can be safely converted into Statements
+     * </p>
+     * @param s Subject
+     * @param p Predicate
+     * @param o Object
+     * @return True if a valid as a statement
+     */
+    public static boolean isValidAsRDF(Node g, Node s, Node p, Node o) {
+        if ( g == null || ( ! g.isURI() && ! g.isBlank() ) )
+            return false;
+        return isValidAsRDF(s, p, o);
+    }
+
+    /** Filter out triples and quads that are "generalized" RDF */
+    public static StreamRDF removeGeneralizedRDF(StreamRDF data) {
+        return new StreamRDFWrapper(data) {
+            @Override
+            public void quad(Quad quad) {
+                if ( ! isValidAsRDF(quad.getGraph(), quad.getSubject(), quad.getPredicate(), quad.getObject()) ) {
+                    // Reject
+                    return;
+                }
+                super.quad(quad);
+            }
+
+            @Override
+            public void triple(Triple triple) {
+                if ( ! isValidAsRDF(triple.getSubject(), triple.getPredicate(), triple.getObject()) ) {
+                    // Reject
+                    return;
+                }
+                super.triple(triple);
+            }
+        };
+    }
 }

jena-arq/src/test/java/org/apache/jena/arq/ARQTestSuite.java

@@ -18,6 +18,11 @@
 
 package org.apache.jena.arq;
 
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.runner.RunWith;
+import org.junit.runners.Suite;
+
 import org.apache.jena.atlas.TC_Atlas_ARQ;
 import org.apache.jena.atlas.legacy.BaseTest2;
 import org.apache.jena.external.Scripts_LangSuiteCG;
@@ -34,10 +39,7 @@
 import org.apache.jena.sys.JenaSystem;
 import org.apache.jena.system.TS_System;
 import org.apache.jena.system.buffering.TS_Buffering;
-import org.junit.AfterClass;
-import org.junit.BeforeClass;
-import org.junit.runner.RunWith;
-import org.junit.runners.Suite;
+import org.apache.jena.util.TS_UtilsARQ;
 
 /**
  * All the ARQ tests
@@ -47,6 +49,8 @@
 @Suite.SuiteClasses( {
     TC_Atlas_ARQ.class,
 
+    TS_UtilsARQ.class,
+
     TC_Riot.class,
 
     TS_System.class,

jena-arq/src/test/java/org/apache/jena/util/TS_UtilsARQ.java

@@ -0,0 +1,29 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.jena.util;
+
+import org.junit.runner.RunWith ;
+import org.junit.runners.Suite ;
+
+@RunWith(Suite.class)
+@Suite.SuiteClasses( {
+    TestNodeUtils.class
+})
+
+public class TS_UtilsARQ {}