if (sourceNode == null)
new Exception(relation + " has no vaild source").printStackTrace();
String weight = cacheManager.getRelationWeightString(relation);
final GSSRelationConnection connection = new GSSRelationConnection(zestGraph,
ZestStyles.CONNECTIONS_DIRECTED, sourceNode, targetNode, relation);
ConnectionDecorator.decoradeConnection(connection, relation, target,
source, weight);
putRelationToCache(connection, relation);