Github user kinow commented on a diff in the pull request:
https://github.com/apache/jena/pull/432#discussion_r194243520
--- Diff:
jena-core/src/main/java/org/apache/jena/util/PrefixMappingUtils.java ---
@@ -0,0 +1,361 @@
+/*
+ * 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 java.util.* ;
+import java.util.function.Consumer ;
+import java.util.stream.Collectors ;
+
+import org.apache.jena.atlas.lib.SetUtils ;
+import org.apache.jena.atlas.lib.Trie ;
+import org.apache.jena.graph.Graph ;
+import org.apache.jena.graph.Node ;
+import org.apache.jena.graph.Triple ;
+import org.apache.jena.graph.impl.WrappedGraph;
+import org.apache.jena.rdf.model.Model ;
+import org.apache.jena.shared.PrefixMapping ;
+import org.apache.jena.shared.impl.PrefixMappingImpl ;
+
+public class PrefixMappingUtils {
+ /**
+ * Return a read-only graph that has the same data (RDF triples) as
the one given, but has a
+ * prefix mapping that only includes "in use " prefixes.
+ * <p>
+ * The prefix mappings of the two graphs are not connected.
+ * Later changes to the prefix mapping of the original graph are not
reflected in the returned graph.
+ * Modifications to the triples conatained in the underlying graph are
reflected.
+ */
+ public static Graph graphInUsePrefixMapping(Graph graph) {
+ final PrefixMapping prefixMapping = calcInUsePrefixMapping(graph) ;
+ prefixMapping.lock() ;
+ Graph graph2 = new WrappedGraph(graph) {
+ @Override
+ public void performAdd(Triple triple)
+ { throw new UnsupportedOperationException() ; }
+
+ @Override
+ public void performDelete(Triple triple)
+ { throw new UnsupportedOperationException() ; }
+
+ @Override
+ public PrefixMapping getPrefixMapping() {
+ return prefixMapping ;
+ }
+ } ;
+ return graph2 ;
+ }
+
+ /**
+ * Analyse the graph to see which prefixes of the graph are in use.
+ * <p>
+ * In the case of overlapping prefixes (where one prefix declaration
is has an initial
+ * URI string which imatches another prefix declaration), all are
included, though
+ * they may not be used when printing (that depends on the output
process). In effect,
+ * this process has "false positives".
+ * <p>
+ * This function does not calculate new prefixes.
+ *
+ * @see #calcInUsePrefixMappingTTL(Graph)
+ */
+ public static PrefixMapping calcInUsePrefixMapping(Graph graph) {
+ PrefixMapping prefixMapping = graph.getPrefixMapping() ;
+ if ( prefixMapping == null )
+ return null ;
+ return calcInUsePrefixMapping(graph, prefixMapping) ;
+ }
+
+ /**
+ * Analyse the graph to see which prefixes of the given {@link
PrefixMapping} are in
+ * use.
+ * <p>
+ * In the case of overlapping prefixes (where one prefix declaration
is has an initial
+ * URI string which imatches another prefix declaration), all are
included, though
+ * they may not be used when printing (that depends on the output
process). In effect,
+ * this process has "false positives".
+ * <p>
+ * This function does not calculate new prefixes.
+ *
+ * @see #calcInUsePrefixMappingTTL(Graph, PrefixMapping)
+ */
+ public static PrefixMapping calcInUsePrefixMapping(Graph graph,
PrefixMapping prefixMapping) {
+
+ /* Method:
+ *
+ * For each URI in the data, look it up in the trie.
+ * after the last ":" for URNs, then see if that is a declared
prefix.
+ *
+ * Exit early if every prefix is accounted for.
+ */
+
+ // Map prefix to URI.
+ Map<String, String> pmap = prefixMapping.getNsPrefixMap() ;
+
+ // Map URI to prefix, with partial lookup (all uri keys that
partly match the URI)
+ Trie<String> trie = new Trie<>() ;
+ // Chnage this to "add(uri, uri)" to calculate the uris.
--- End diff --
s/Chnage/Change
---
