diff --git a/hoot-core/src/main/cpp/hoot/core/algorithms/extractors/RelationMemberSimilarityExtractor.cpp b/hoot-core/src/main/cpp/hoot/core/algorithms/extractors/RelationMemberSimilarityExtractor.cpp
new file mode 100644
index 0000000..b4aa869
--- /dev/null
+++ b/hoot-core/src/main/cpp/hoot/core/algorithms/extractors/RelationMemberSimilarityExtractor.cpp
@@ -0,0 +1,128 @@
+/*
+ * This file is part of Hootenanny.
+ *
+ * Hootenanny is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * --------------------------------------------------------------------
+ *
+ * The following copyright notices are generated automatically. If you
+ * have a new notice to add, please use the format:
+ * " * @copyright Copyright ..."
+ * This will properly maintain the copyright information. DigitalGlobe
+ * copyrights will be updated automatically.
+ *
+ * @copyright Copyright (C) 2020 DigitalGlobe (http://www.digitalglobe.com/)
+ */
+#include "RelationMemberSimilarityExtractor.h"
+
+// hoot
+#include <hoot/core/util/Factory.h>
+#include <hoot/core/util/Log.h>
+#include <hoot/core/util/CollectionUtils.h>
+#include <hoot/core/elements/RelationMemberComparison.h>
+
+namespace hoot
+{
+
+HOOT_FACTORY_REGISTER(FeatureExtractor, RelationMemberSimilarityExtractor)
+
+RelationMemberSimilarityExtractor::RelationMemberSimilarityExtractor()
+{
+}
+
+double RelationMemberSimilarityExtractor::extract(
+ const OsmMap& map, const std::shared_ptr<const Element>& target,
+ const std::shared_ptr<const Element>& candidate) const
+{
+ if (target->getElementType() != ElementType::Relation ||
+ candidate->getElementType() != ElementType::Relation)
+ {
+ return 0.0;
+ }
+
+ const ConstRelationPtr targetRelation = std::dynamic_pointer_cast<const Relation>(target);
+ const ConstRelationPtr candidateRelation =
+ std::dynamic_pointer_cast<const Relation>(candidate);
+ if (targetRelation && candidateRelation)
+ {
+ LOG_VART(targetRelation->getTags().get("name"));
+ LOG_VART(candidateRelation->getTags().get("name"));
+ LOG_VART(targetRelation->getType());
+ LOG_VART(candidateRelation->getType());
+
+ QSet<ElementId> targetMemberIds =
+ CollectionUtils::stdSetToQSet(targetRelation->getMemberIds());
+ LOG_VART(targetMemberIds.size());
+ //LOG_VART(targetMemberIds);
+ QSet<ElementId> candidateMemberIds =
+ CollectionUtils::stdSetToQSet(candidateRelation->getMemberIds());
+ LOG_VART(candidateMemberIds.size());
+ //LOG_VART(candidateMemberIds);
+ const int totalMembers = targetMemberIds.size() + candidateMemberIds.size();
+ LOG_VART(totalMembers);
+
+ if (targetMemberIds.size() == 0 || candidateMemberIds.size() == 0)
+ {
+ return 0.0;
+ }
+
+ int numSharedMembers = 0;
+
+ QSet<RelationMemberComparison> targetMemberComps;
+ const std::vector<RelationData::Entry> targetMembers = targetRelation->getMembers();
+ for (size_t i = 0; i < targetMembers.size(); i++)
+ {
+ const RelationData::Entry member = targetMembers[i];
+ ConstElementPtr memberElement = map.getElement(member.getElementId());
+ if (memberElement)
+ {
+ // not sure how to get around this const cast...
+ ElementPtr memberElement2 = std::const_pointer_cast<Element>(memberElement);
+ targetMemberComps.insert(
+ RelationMemberComparison(memberElement2, map, member.getRole(), true));
+ }
+ }
+ LOG_VART(targetMemberComps.size());
+
+ QSet<RelationMemberComparison> candidateMemberComps;
+ const std::vector<RelationData::Entry> candidateMembers = candidateRelation->getMembers();
+ for (size_t i = 0; i < candidateMembers.size(); i++)
+ {
+ const RelationData::Entry member = candidateMembers[i];
+ ConstElementPtr memberElement = map.getElement(member.getElementId());
+ if (memberElement)
+ {
+ ElementPtr memberElement2 = std::const_pointer_cast<Element>(memberElement);
+ candidateMemberComps.insert(
+ RelationMemberComparison(memberElement2, map, member.getRole(), true));
+ }
+ }
+ LOG_VART(candidateMemberComps.size());
+
+ QSet<RelationMemberComparison> intersection =
+ targetMemberComps.intersect(candidateMemberComps);
+ LOG_VART(intersection);
+ numSharedMembers = intersection.size();
+ LOG_VART(numSharedMembers);
+
+ // calculate Jaccard
+ const double similarity = (double)numSharedMembers / (double)totalMembers;
+ LOG_VART(similarity);
+ return similarity;
+ }
+
+ return 0.0;
+}
+
+}