Strabon

changeset 1167:bae12a2322e4 temporals

cloned behaviour of the SpatialJoinOptimizer to apply for the temporal case too, in order to avoid the production of cartesian products in temporal joins
author Konstantina Bereta <Konstantina.Bereta@di.uoa.gr>
date Fri May 10 16:03:20 2013 +0300 (2013-05-10)
parents 1d3afe469324
children c003d2c1a053
files evaluation/src/main/java/org/openrdf/query/algebra/evaluation/impl/TemporalJoinOptimizer.java generaldb/src/main/java/org/openrdf/sail/generaldb/optimizers/GeneralDBQueryOptimizer.java generaldb/src/main/java/org/openrdf/sail/generaldb/optimizers/GeneralDBSelectQueryOptimizer.java runtime/src/test/resources/temporal-periods.nq
line diff
     1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/evaluation/src/main/java/org/openrdf/query/algebra/evaluation/impl/TemporalJoinOptimizer.java	Fri May 10 16:03:20 2013 +0300
     1.3 @@ -0,0 +1,733 @@
     1.4 +/**
     1.5 + * This Source Code Form is subject to the terms of the Mozilla Public
     1.6 + * License, v. 2.0. If a copy of the MPL was not distributed with this
     1.7 + * file, You can obtain one at http://mozilla.org/MPL/2.0/.
     1.8 + * 
     1.9 + * Copyright (C) 2010, 2011, 2012, Pyravlos Team
    1.10 + * 
    1.11 + * http://www.strabon.di.uoa.gr/
    1.12 + */
    1.13 +package org.openrdf.query.algebra.evaluation.impl;
    1.14 +
    1.15 +import java.util.ArrayList;
    1.16 +import java.util.HashMap;
    1.17 +import java.util.Iterator;
    1.18 +import java.util.LinkedHashSet;
    1.19 +import java.util.List;
    1.20 +import java.util.Map;
    1.21 +import java.util.Set;
    1.22 +
    1.23 +import org.openrdf.query.BindingSet;
    1.24 +import org.openrdf.query.Dataset;
    1.25 +import org.openrdf.query.algebra.Compare;
    1.26 +import org.openrdf.query.algebra.Extension;
    1.27 +import org.openrdf.query.algebra.Filter;
    1.28 +import org.openrdf.query.algebra.FunctionCall;
    1.29 +import org.openrdf.query.algebra.Join;
    1.30 +import org.openrdf.query.algebra.LeftJoin;
    1.31 +import org.openrdf.query.algebra.MathExpr;
    1.32 +import org.openrdf.query.algebra.Or;
    1.33 +import org.openrdf.query.algebra.QueryModelNode;
    1.34 +import org.openrdf.query.algebra.StatementPattern;
    1.35 +import org.openrdf.query.algebra.StatementPattern.Scope;
    1.36 +import org.openrdf.query.algebra.TupleExpr;
    1.37 +import org.openrdf.query.algebra.ValueExpr;
    1.38 +import org.openrdf.query.algebra.Var;
    1.39 +import org.openrdf.query.algebra.evaluation.function.Function;
    1.40 +import org.openrdf.query.algebra.evaluation.function.FunctionRegistry;
    1.41 +import org.openrdf.query.algebra.evaluation.function.temporal.stsparql.relation.TemporalRelationFunc;
    1.42 +import org.openrdf.query.algebra.helpers.QueryModelVisitorBase;
    1.43 +import org.openrdf.query.algebra.helpers.StatementPatternCollector;
    1.44 +
    1.45 +/**
    1.46 + * A query optimizer that re-orders nested Joins.
    1.47 + * 
    1.48 + * @author Manos Karpathiotakis <mk@di.uoa.gr>
    1.49 + */
    1.50 +public class TemporalJoinOptimizer 
    1.51 +//implements QueryOptimizer //Removed it consciously 
    1.52 +{
    1.53 +
    1.54 +
    1.55 +	//private Set<String> existingVars = new TreeSet<String>();
    1.56 +	/**
    1.57 +	 * Applies generally applicable optimizations: path expressions are sorted
    1.58 +	 * from more to less specific.
    1.59 +	 * 
    1.60 +	 * @param tupleExpr
    1.61 +	 */
    1.62 +	public void optimize(TupleExpr tupleExpr, Dataset dataset, BindingSet bindings, List<TupleExpr> temporalJoins) {
    1.63 +		tupleExpr.visit(new JoinVisitor(temporalJoins));
    1.64 +	}
    1.65 +
    1.66 +	protected class JoinVisitor extends QueryModelVisitorBase<RuntimeException> {
    1.67 +		
    1.68 +		
    1.69 +		
    1.70 +		public JoinVisitor(List<TupleExpr> temporalJoins) {
    1.71 +			super();
    1.72 +			this.temporalJoins = temporalJoins;
    1.73 +		}
    1.74 +
    1.75 +		
    1.76 +		private List<TupleExpr> temporalJoins;
    1.77 +		//buffer with a var as a second argument
    1.78 +		private boolean problematicBuffer = false;
    1.79 +
    1.80 +		//indicates whether a metric expression contains a temporal function call	
    1.81 +		private boolean containsTemporal = false;
    1.82 +		private boolean optimizableMetricOrProperty = true;
    1.83 +
    1.84 +		private int thematicJoinsSize = 0;
    1.85 +
    1.86 +		
    1.87 +		Map<TupleExpr, List<Var>> temporalFilters = new HashMap<TupleExpr, List<Var>>();
    1.88 +
    1.89 +		@Override
    1.90 +		public void meet(Join node) {
    1.91 +
    1.92 +			//XXX NOTE: NOT OPTIMIZING CONTENTS OF OPTIONAL CLAUSE!!!
    1.93 +			//Reason1: Errors occurred in the condition of the LeftJoin containing the optional subgraph
    1.94 +
    1.95 +			//Not as successful as I hoped. Some OPTIONAL clauses may pass
    1.96 +			if(parentIsOptional(node))
    1.97 +			{
    1.98 +				return;
    1.99 +			}
   1.100 +			//			if(node.getParentNode() instanceof LeftJoin)
   1.101 +			//			{
   1.102 +			//				return;
   1.103 +			//			}
   1.104 +
   1.105 +			// Recursively get the join arguments
   1.106 +			List<TupleExpr> joinArgs = getJoinArgs(node, new ArrayList<TupleExpr>());
   1.107 +
   1.108 +			if(joinArgs == null)
   1.109 +			{
   1.110 +				//2nd mechanism to avoid OPTIONAL clauses from passing
   1.111 +				return;
   1.112 +			}
   1.113 +
   1.114 +
   1.115 +			Map<TupleExpr, List<Var>> varsMap = new /*Linked*/HashMap<TupleExpr, List<Var>>();
   1.116 +
   1.117 +			for (TupleExpr tupleExpr : joinArgs) {
   1.118 +				varsMap.put(tupleExpr, getStatementPatternVars(tupleExpr));
   1.119 +
   1.120 +			}
   1.121 +
   1.122 +			//Now I have all the info I need. Just need to structure it efficiently
   1.123 +			int allNodes = varsMap.size() + temporalFilters.size();
   1.124 +			thematicJoinsSize = varsMap.size();
   1.125 +			//careful with positions on the diagonal! Do not utilize them!
   1.126 +			int joinsGraph[][] = new int[allNodes][allNodes];
   1.127 +
   1.128 +			//prints for debug
   1.129 +			//			Set<TupleExpr> allExprs = varsMap.keySet();
   1.130 +			//			System.out.println(allExprs.toString());
   1.131 +			//			
   1.132 +			//			Set<TupleExpr> allFilters = temporalFilters.keySet();
   1.133 +			//			System.out.println(allFilters.toString());
   1.134 +
   1.135 +			//Thematic part first
   1.136 +			int i = 0;
   1.137 +
   1.138 +			for(List<Var> listHorizontal : varsMap.values())
   1.139 +			{
   1.140 +				int j = 0;
   1.141 +				int k = 0;
   1.142 +
   1.143 +				//Other thematics
   1.144 +				for(List<Var> listVertical : varsMap.values())
   1.145 +				{
   1.146 +					if(i==j)
   1.147 +					{
   1.148 +						j++;
   1.149 +						continue;
   1.150 +					}
   1.151 +
   1.152 +
   1.153 +					joinsGraph[i][j] = sameVar(listHorizontal, listVertical);
   1.154 +
   1.155 +					j++;
   1.156 +				}
   1.157 +
   1.158 +				//Temporals
   1.159 +				for(List<Var> listVertical : temporalFilters.values())
   1.160 +				{
   1.161 +
   1.162 +					joinsGraph[i][k+varsMap.size()] = sameVar(listHorizontal, listVertical);
   1.163 +
   1.164 +					k++;
   1.165 +				}
   1.166 +
   1.167 +				i++;
   1.168 +			}
   1.169 +
   1.170 +			//Now for the temporal horizontal nodes
   1.171 +			i = varsMap.size();
   1.172 +			for(List<Var> listHorizontal : temporalFilters.values())
   1.173 +			{
   1.174 +				int j = 0;
   1.175 +				int k = 0;
   1.176 +
   1.177 +				//Other thematics
   1.178 +				for(List<Var> listVertical : varsMap.values())
   1.179 +				{
   1.180 +
   1.181 +					joinsGraph[i][j] = sameVar(listHorizontal, listVertical);
   1.182 +
   1.183 +					j++;
   1.184 +				}
   1.185 +
   1.186 +				//Temporals
   1.187 +				for(List<Var> listVertical : temporalFilters.values())
   1.188 +				{
   1.189 +					if(i==k+varsMap.size())
   1.190 +					{
   1.191 +						k++;
   1.192 +						continue;
   1.193 +					}
   1.194 +
   1.195 +					joinsGraph[i][k+varsMap.size()] =sameVar(listHorizontal, listVertical);
   1.196 +
   1.197 +					k++;
   1.198 +				}
   1.199 +
   1.200 +				i++;
   1.201 +			}
   1.202 +
   1.203 +			//Checking graph to be sure
   1.204 +			/*
   1.205 +			for(int a = 0; a < allNodes; a++)
   1.206 +			{
   1.207 +				for(int b = 0; b < allNodes; b++)
   1.208 +				{
   1.209 +					System.out.print(joinsGraph[a][b]+" ");
   1.210 +
   1.211 +				}
   1.212 +				System.out.println("");
   1.213 +			}
   1.214 +			*/
   1.215 +
   1.216 +			//Time to construct ordered sequence of joins + filters
   1.217 +			List<TupleExpr> orderedJoinArgs = new ArrayList<TupleExpr>(allNodes);
   1.218 +			//maybe I won't need all the positions -> some temporal joins may not be utilized
   1.219 +			List<Integer> tempList = new ArrayList<Integer>(allNodes);
   1.220 +			List<Integer> pathList = new ArrayList<Integer>();
   1.221 +			List<Integer> finalList = new ArrayList<Integer>();
   1.222 +			Set<Var> varsTillNow = new LinkedHashSet<Var>();
   1.223 +			for(int row = 0 ; row < allNodes ; row++)
   1.224 +			{
   1.225 +				tempList.add(row);
   1.226 +				createOrderedJoins(joinsGraph, row, row, 1, varsTillNow, tempList, pathList, finalList);
   1.227 +				pathList.clear();
   1.228 +				if(finalList.size() == allNodes)
   1.229 +				{
   1.230 +					break;
   1.231 +				}
   1.232 +
   1.233 +			}
   1.234 +
   1.235 +			/*
   1.236 +			System.out.println("*--REWRITTEN TREE--**");
   1.237 +			System.out.println(finalList.toString());
   1.238 +			*/
   1.239 +
   1.240 +			int varsMapSize = varsMap.size();
   1.241 +			for(Integer position : finalList)
   1.242 +			{
   1.243 +				if(position<varsMapSize)//thematic!
   1.244 +				{
   1.245 +					int count = 0;
   1.246 +					Iterator it = varsMap.entrySet().iterator();
   1.247 +
   1.248 +					while (it.hasNext())
   1.249 +					{
   1.250 +						{
   1.251 +							Map.Entry entry = (Map.Entry)it.next();
   1.252 +							if(count == position)
   1.253 +							{
   1.254 +								orderedJoinArgs.add((TupleExpr) entry.getKey());
   1.255 +
   1.256 +								it.remove();
   1.257 +								varsMapSize--;
   1.258 +
   1.259 +								for(int fix = 0 ; fix < finalList.size(); fix++)
   1.260 +								{
   1.261 +									if(finalList.get(fix) > position)
   1.262 +									{
   1.263 +										int reduced = finalList.get(fix) - 1;
   1.264 +										finalList.set(fix, reduced);
   1.265 +
   1.266 +									}
   1.267 +								}
   1.268 +								break;
   1.269 +							}
   1.270 +							count++;
   1.271 +						}
   1.272 +					}
   1.273 +				}
   1.274 +				else//temporal!
   1.275 +				{
   1.276 +					int count = 0;
   1.277 +					Iterator it = temporalFilters.entrySet().iterator();
   1.278 +					while (it.hasNext())
   1.279 +					{
   1.280 +						{
   1.281 +							Map.Entry entry = (Map.Entry)it.next();
   1.282 +							if(count == position - varsMapSize)
   1.283 +							{
   1.284 +								//If I keep record of this entry, I can use the info later to avoid duplicate filters
   1.285 +								temporalJoins.add((TupleExpr) entry.getKey());
   1.286 +								//
   1.287 +								orderedJoinArgs.add((TupleExpr) entry.getKey());
   1.288 +								it.remove();
   1.289 +								for(int fix = 0 ; fix < finalList.size(); fix++)
   1.290 +								{
   1.291 +									if(finalList.get(fix) > position)
   1.292 +									{
   1.293 +										int reduced = finalList.get(fix) - 1;
   1.294 +										finalList.set(fix, reduced);
   1.295 +									}
   1.296 +								}
   1.297 +								break;
   1.298 +							}
   1.299 +							count++;
   1.300 +						}
   1.301 +					}
   1.302 +				}
   1.303 +
   1.304 +			}
   1.305 +			//Must take care of the remainders as well!
   1.306 +			Iterator it = varsMap.entrySet().iterator();
   1.307 +			while (it.hasNext())
   1.308 +			{
   1.309 +				Map.Entry entry = (Map.Entry)it.next();
   1.310 +				orderedJoinArgs.add((TupleExpr) entry.getKey());
   1.311 +				it.remove();
   1.312 +			}
   1.313 +
   1.314 +			TupleExpr replacement = orderedJoinArgs.get(0);
   1.315 +			for (int ii = 1; ii < orderedJoinArgs.size(); ii++) {
   1.316 +				replacement = new Join(replacement, orderedJoinArgs.get(ii));
   1.317 +			}
   1.318 +
   1.319 +			// Replace old join hierarchy
   1.320 +			node.replaceWith(replacement);
   1.321 +
   1.322 +		}
   1.323 +
   1.324 +
   1.325 +		public boolean parentIsOptional(QueryModelNode node)
   1.326 +		{
   1.327 +			if(node.getParentNode() == null)
   1.328 +			{
   1.329 +				return false;
   1.330 +			}
   1.331 +			else if(node.getParentNode() instanceof LeftJoin)
   1.332 +			{
   1.333 +				return true;
   1.334 +			}
   1.335 +			else
   1.336 +			{
   1.337 +				return parentIsOptional(node.getParentNode());
   1.338 +			}
   1.339 +		}
   1.340 +
   1.341 +		/**
   1.342 +		 * General Comment: If more than one function exists in the query and can be used to perform the join, no preference is shown 
   1.343 +		 * on which function will actually be used for this purpose. This could cause an issue if ST_Disjoint is the one finally used, 
   1.344 +		 * as the index won't be used for the evaluation in this case. Perhaps I should include some 'priority'
   1.345 +		 */
   1.346 +		@Override
   1.347 +		public void meet(Filter node) {
   1.348 +
   1.349 +			/**
   1.350 +			 * Filter node must not be in OPTIONAL clause!
   1.351 +			 * After all, unneeded check. If an optional exists, the 'Filter' tuple expression
   1.352 +			 * is removed and only the Function Calls remain
   1.353 +			 */
   1.354 +			if(!withinHaving(node))
   1.355 +			{
   1.356 +				//if(!(node.getParentNode() instanceof LeftJoin))
   1.357 +				//{
   1.358 +				//XXX Ignore OR in Filters for now! (perhaps permanently)
   1.359 +				if(!(node.getCondition() instanceof Or))
   1.360 +				{
   1.361 +					if(node.getCondition() instanceof FunctionCall)
   1.362 +					{
   1.363 +						//Only interested in temporal ones
   1.364 +						if(isRelevantTemporalFunc((FunctionCall) node.getCondition()))
   1.365 +						{
   1.366 +							//Have to retrieve all nested variables and other info
   1.367 +
   1.368 +							//1.Retrieve varNames
   1.369 +							List<Var> varList = getFunctionCallVars((FunctionCall) node.getCondition());
   1.370 +
   1.371 +							//Cannot optimize buffer constructs when their 2nd argument is a 
   1.372 +							//thematic var, because I can't manipulate the order of the 
   1.373 +							//numeric_values table
   1.374 +							if(!problematicBuffer)
   1.375 +							{
   1.376 +								//XXX I cannot process cases involving more than 2 arguments in the temporal join!
   1.377 +								// They transcend the theta join level!
   1.378 +								//							if(varList.size()<3)
   1.379 +
   1.380 +								//if the arguments are not 2, I am essentially doing a selection!
   1.381 +								//No reason to push into optimizer then
   1.382 +								if(varList.size()==2)
   1.383 +								{
   1.384 +									//Add all important info about this temporal relationship to the appropriate structure
   1.385 +									//temporalFilters.add(new TemporalFilterInfo(varList, (FunctionCall) node.getCondition()));
   1.386 +									Filter toEnter = node.clone();
   1.387 +
   1.388 +									/**
   1.389 +									 * VERY CAREFUL HERE! 
   1.390 +									 * Reason I did this: If not, I would carry a copy of the whole expression for
   1.391 +									 * every extra filter of my query!
   1.392 +									 * -DUMMY-!!!
   1.393 +									 */
   1.394 +									StatementPattern t = new StatementPattern();
   1.395 +									t.setSubjectVar(new Var("-dummy-temporal"));
   1.396 +									t.setPredicateVar(new Var("-dummy-temporal"));
   1.397 +									t.setObjectVar(new Var("-dummy-temporal"));
   1.398 +									t.setScope(Scope.DEFAULT_CONTEXTS);
   1.399 +									toEnter.setArg(t);
   1.400 +
   1.401 +									if(!temporalFilters.containsKey(toEnter))
   1.402 +									{
   1.403 +										temporalFilters.put(toEnter,varList);
   1.404 +									}
   1.405 +								}
   1.406 +								problematicBuffer = false;
   1.407 +							}
   1.408 +						}
   1.409 +					}
   1.410 +					//Metrics
   1.411 +					//I have a similar problematic case with the one occurring in Buffer! 
   1.412 +					//Cannot manipulate the join order when I am dealing with numerics!
   1.413 +					//Therefore, I cannot use a numeric field (a numeric var) to alter the join sequence
   1.414 +					else if(node.getCondition() instanceof Compare)
   1.415 +					{
   1.416 +						containsTemporal = false;
   1.417 +						List<Var> allVars = new ArrayList<Var>(getVarsInMetricOrProperty(node.getCondition()));
   1.418 +						if(containsTemporal&&optimizableMetricOrProperty)
   1.419 +						{
   1.420 +							//if the arguments are not 2, I am essentially doing a selection!
   1.421 +							//No reason to push into optimizer then
   1.422 +							if(allVars.size()==2)
   1.423 +								//if(allVars.size()<3)
   1.424 +							{
   1.425 +								//Add all important info about this temporal relationship to the appropriate structure
   1.426 +								//temporalFilters.add(new TemporalFilterInfo(varList, (FunctionCall) node.getCondition()));
   1.427 +								Filter toEnter = node.clone();
   1.428 +
   1.429 +								StatementPattern t = new StatementPattern();
   1.430 +								t.setSubjectVar(new Var("-dummy-"));
   1.431 +								t.setPredicateVar(new Var("-dummy-"));
   1.432 +								t.setObjectVar(new Var("-dummy-"));
   1.433 +								t.setScope(Scope.DEFAULT_CONTEXTS);
   1.434 +								toEnter.setArg(t);
   1.435 +
   1.436 +								if(!temporalFilters.containsKey(toEnter))
   1.437 +								{
   1.438 +									temporalFilters.put(toEnter,allVars);
   1.439 +								}
   1.440 +							}
   1.441 +							containsTemporal = false;
   1.442 +						}
   1.443 +						optimizableMetricOrProperty = true;
   1.444 +					}
   1.445 +
   1.446 +				}
   1.447 +				//}
   1.448 +			}
   1.449 +
   1.450 +			//Last thing to do is ensuring the entire tree is traversed
   1.451 +			node.visitChildren(this);
   1.452 +
   1.453 +		}
   1.454 +
   1.455 +
   1.456 +		/**
   1.457 +		 * Helper Functions
   1.458 +		 */
   1.459 +
   1.460 +		/**
   1.461 +		 * Used to find out whether the Filter expr we are currently visiting is located inside
   1.462 +		 * a HAVING clause.
   1.463 +		 * 
   1.464 +		 * From what I have seen so far, it seems that if this is the case, its arg (or one of the following FILTER args in 
   1.465 +		 * the case of disjunction/conjunction) will be an Extension expr followed by a GROUP expr
   1.466 +		 */
   1.467 +		private boolean withinHaving(Filter expr)
   1.468 +		{
   1.469 +			if(expr.getArg() instanceof Extension)
   1.470 +			{
   1.471 +				return true;
   1.472 +			}
   1.473 +			else if(expr.getArg() instanceof Filter)
   1.474 +			{
   1.475 +				return withinHaving((Filter) expr.getArg());
   1.476 +			}
   1.477 +			else
   1.478 +			{
   1.479 +				return false;
   1.480 +			}
   1.481 +		}
   1.482 +
   1.483 +		private <L extends List<TupleExpr>> L getJoinArgs(TupleExpr tupleExpr, L joinArgs) {
   1.484 +			if (tupleExpr instanceof Join) {
   1.485 +				Join join = (Join)tupleExpr;
   1.486 +				if(getJoinArgs(join.getLeftArg(), joinArgs) == null)
   1.487 +					return null;
   1.488 +				if(getJoinArgs(join.getRightArg(), joinArgs) == null)
   1.489 +					return null;
   1.490 +			}
   1.491 +			else if(tupleExpr instanceof LeftJoin) 
   1.492 +			{
   1.493 +				//Trying to avoid OPTIONAL clauses from passing
   1.494 +				return null;
   1.495 +			}
   1.496 +			else 
   1.497 +			{
   1.498 +				joinArgs.add(tupleExpr);
   1.499 +			}
   1.500 +
   1.501 +			return joinArgs;
   1.502 +		}
   1.503 +
   1.504 +		private List<Var> getStatementPatternVars(TupleExpr tupleExpr) {
   1.505 +			List<StatementPattern> stPatterns = StatementPatternCollector.process(tupleExpr);
   1.506 +			List<Var> varList = new ArrayList<Var>(stPatterns.size() * 4);
   1.507 +			for (StatementPattern sp : stPatterns) {
   1.508 +				sp.getVars(varList);
   1.509 +			}
   1.510 +			return varList;
   1.511 +		}
   1.512 +
   1.513 +		/**
   1.514 +		 * temporalContent: Used to declare that this expression does include some temporal 
   1.515 +		 * content and an attempt should be made to use it in the joins' optimization process
   1.516 +		 */
   1.517 +		private Set<Var> getVarsInMetricOrProperty(ValueExpr expr)
   1.518 +		{
   1.519 +			Set<Var> allVars = new LinkedHashSet<Var>();
   1.520 +
   1.521 +			if(expr instanceof Compare)
   1.522 +			{
   1.523 +				allVars.addAll(getVarsInMetricOrProperty(((Compare) expr).getLeftArg()));
   1.524 +				allVars.addAll(getVarsInMetricOrProperty(((Compare) expr).getRightArg()));
   1.525 +			}
   1.526 +			else if(expr instanceof MathExpr)
   1.527 +			{
   1.528 +				allVars.addAll(getVarsInMetricOrProperty(((MathExpr) expr).getLeftArg()));
   1.529 +				allVars.addAll(getVarsInMetricOrProperty(((MathExpr) expr).getRightArg()));
   1.530 +			}
   1.531 +			else if(expr instanceof FunctionCall )
   1.532 +			{
   1.533 +				if(isRelevantTemporalFunc((FunctionCall) expr))
   1.534 +				{
   1.535 +					/**
   1.536 +					 * There is a point in continuing the search recursively ONLY 
   1.537 +					 * if I reach this case. Otherwise, the function call
   1.538 +					 * may not refer to a temporal function
   1.539 +					 */
   1.540 +					this.containsTemporal = true;
   1.541 +					allVars.addAll(getFunctionCallVars((FunctionCall) expr));
   1.542 +
   1.543 +				}
   1.544 +			}
   1.545 +			else if(expr instanceof Var)
   1.546 +			{
   1.547 +				if(!(expr.getParentNode() instanceof FunctionCall))
   1.548 +				{
   1.549 +					//Cannot manipulate the join order when I am dealing with numerics!
   1.550 +					//Therefore, I cannot use a numeric field (a numeric var) to alter the join sequence
   1.551 +					this.optimizableMetricOrProperty = false;
   1.552 +				}
   1.553 +				if(!allVars.contains(expr))
   1.554 +				{
   1.555 +					allVars.add((Var) expr);
   1.556 +				}
   1.557 +			}
   1.558 +
   1.559 +			return allVars;
   1.560 +		}
   1.561 +
   1.562 +		private boolean isRelevantTemporalFunc(FunctionCall functionCall)
   1.563 +		{
   1.564 +			Function function = FunctionRegistry.getInstance().get(functionCall.getURI());
   1.565 +			if(function instanceof org.openrdf.query.algebra.evaluation.function.temporal.stsparql.construct.TemporalConstructFunc )
   1.566 +			{
   1.567 +				//TODO may have to comment this part again
   1.568 +				//uncommented because I use this function in the case of metrics
   1.569 +				return true;
   1.570 +			}
   1.571 +			else if(function instanceof TemporalRelationFunc)
   1.572 +			{
   1.573 +				return true;
   1.574 +			}
   1.575 +			return false;
   1.576 +		}
   1.577 +
   1.578 +		private List<Var> getFunctionCallVars(FunctionCall functionCall) {
   1.579 +			List<Var> varList = new ArrayList<Var>();
   1.580 +			int argList = 0;
   1.581 +			for(ValueExpr expr : functionCall.getArgs())
   1.582 +			{
   1.583 +				argList++;
   1.584 +				if(expr instanceof Var)
   1.585 +				{
   1.586 +					//					if(!existingVars.contains(((Var) expr).getName()))
   1.587 +					//					{
   1.588 +					//						existingVars.add(((Var) expr).getName());
   1.589 +					//					}
   1.590 +
   1.591 +					if(!varList.contains(expr))
   1.592 +					{
   1.593 +						//Was using this code when I tried to incorporate the Buffer case buffer(?Temporal,?thematic)
   1.594 +						if(argList == 2 && functionCall.getURI().equals("http://strdf.di.uoa.gr/ontology#buffer"))
   1.595 +						{
   1.596 +							problematicBuffer = true;
   1.597 +						}
   1.598 +						varList.add((Var) expr);
   1.599 +					}
   1.600 +
   1.601 +				}
   1.602 +				else if(expr instanceof FunctionCall)
   1.603 +				{
   1.604 +					varList.addAll(getFunctionCallVars((FunctionCall) expr));
   1.605 +				}
   1.606 +				//TODO Should I add any additional cases? I don't think so
   1.607 +				else
   1.608 +				{
   1.609 +					continue;
   1.610 +				}
   1.611 +			}
   1.612 +			return varList;
   1.613 +		}
   1.614 +
   1.615 +		/**
   1.616 +		 * Both lists belong to either a thematic node (St.Pattern) or a temporal node (Filter)
   1.617 +		 * Comparing the vars with each other to discover links of the query graph
   1.618 +		 * @param list1 
   1.619 +		 * @param list2
   1.620 +		 * @return
   1.621 +		 */
   1.622 +		private int sameVar(List<Var> list1, List<Var> list2)
   1.623 +		{
   1.624 +			for(Var var : list1)
   1.625 +			{
   1.626 +				if(list2.contains(var))
   1.627 +				{
   1.628 +					return 1;
   1.629 +				}
   1.630 +			}
   1.631 +
   1.632 +			return 0;
   1.633 +		}
   1.634 +
   1.635 +
   1.636 +
   1.637 +
   1.638 +
   1.639 +		//Input: a single line of the table
   1.640 +		//NOTE: NO LOOPS! CAREFUL!!
   1.641 +		private boolean createOrderedJoins(int table[][], int lineToScan,int columnToSkip, 
   1.642 +				int pathLen, Set<Var> varsTillNow, List<Integer> tempList, List<Integer> pathList, List<Integer> finalList)
   1.643 +		{
   1.644 +			boolean success = false;
   1.645 +			int dims = table.length;
   1.646 +
   1.647 +			int j;
   1.648 +
   1.649 +			//dims: all arguments
   1.650 +			for(j = 0; j < dims; j++)
   1.651 +			{
   1.652 +				if(j == columnToSkip)
   1.653 +				{
   1.654 +					continue;
   1.655 +				}
   1.656 +
   1.657 +				//A connection exists!
   1.658 +				if(table[lineToScan][j]>0)
   1.659 +				{
   1.660 +					//Don't want my graph to have circles!!!
   1.661 +					if(!tempList.contains(j)&&!pathList.contains(j))
   1.662 +					{
   1.663 +						if(j >= thematicJoinsSize) //aka if(temporalFilters.size() > 0)
   1.664 +						{
   1.665 +							List<Var> thisFilterVars = null;
   1.666 +							int count = 0;
   1.667 +							for(List<Var> vars : temporalFilters.values())
   1.668 +							{
   1.669 +								if(count == j - thematicJoinsSize)
   1.670 +								{
   1.671 +									thisFilterVars = vars;
   1.672 +									break;
   1.673 +								}
   1.674 +								count++;
   1.675 +							}
   1.676 +							if(!varsTillNow.isEmpty())
   1.677 +							{
   1.678 +								if(varsTillNow.containsAll(thisFilterVars))
   1.679 +								{
   1.680 +									continue;
   1.681 +								}
   1.682 +							}
   1.683 +
   1.684 +							//varsTillNow.add(thisFilterVars.get(1));
   1.685 +							varsTillNow.addAll(thisFilterVars);
   1.686 +
   1.687 +						}
   1.688 +
   1.689 +						tempList.add((Integer)j);
   1.690 +						pathLen++;
   1.691 +						if(pathLen == dims)
   1.692 +						{
   1.693 +							//End of recursion
   1.694 +							pathList.addAll(tempList);
   1.695 +							tempList.clear();
   1.696 +							finalList.clear();
   1.697 +							finalList.addAll(pathList);
   1.698 +
   1.699 +							return true;
   1.700 +						}
   1.701 +
   1.702 +						//Recurse
   1.703 +						success = createOrderedJoins(table, j, lineToScan, pathLen, varsTillNow, tempList, pathList, finalList);
   1.704 +
   1.705 +						//Success = true => recursion ended with pathLen = maxLen
   1.706 +						if(success)
   1.707 +						{
   1.708 +							return true;
   1.709 +						}
   1.710 +						else
   1.711 +						{	
   1.712 +							//end of a path originating from this node was found -> find an additional path (if exists)
   1.713 +							continue;
   1.714 +						}
   1.715 +					}
   1.716 +				}
   1.717 +			}
   1.718 +			//To reach this place means the end of a path was found 
   1.719 +			pathList.addAll(tempList);
   1.720 +			tempList.clear();
   1.721 +			if(pathList.size() > finalList.size())
   1.722 +			{
   1.723 +				finalList.clear();
   1.724 +				finalList.addAll(pathList);
   1.725 +				if(finalList.size() == dims)
   1.726 +				{
   1.727 +					return true;
   1.728 +				}
   1.729 +			}
   1.730 +			return false;			
   1.731 +		}
   1.732 +
   1.733 +	}
   1.734 +
   1.735 +
   1.736 +}
     2.1 --- a/generaldb/src/main/java/org/openrdf/sail/generaldb/optimizers/GeneralDBQueryOptimizer.java	Thu May 09 14:46:55 2013 +0300
     2.2 +++ b/generaldb/src/main/java/org/openrdf/sail/generaldb/optimizers/GeneralDBQueryOptimizer.java	Fri May 10 16:03:20 2013 +0300
     2.3 @@ -19,6 +19,7 @@
     2.4  import org.openrdf.query.algebra.evaluation.impl.DisjunctiveConstraintOptimizer;
     2.5  import org.openrdf.query.algebra.evaluation.impl.SameTermFilterOptimizer;
     2.6  import org.openrdf.query.algebra.evaluation.impl.SpatialJoinOptimizer;
     2.7 +import org.openrdf.query.algebra.evaluation.impl.TemporalJoinOptimizer;
     2.8  import org.openrdf.query.algebra.evaluation.impl.stSPARQLConstantOptimizer;
     2.9  import org.openrdf.sail.generaldb.GeneralDBValueFactory;
    2.10  import org.openrdf.sail.generaldb.schema.BNodeTable;
    2.11 @@ -47,6 +48,10 @@
    2.12  	
    2.13  	//Addition to locate duplicate filters caused by the SpatialJoinOptimizer
    2.14  	List<TupleExpr> spatialJoins = new ArrayList<TupleExpr>();
    2.15 +	
    2.16 +	//same applies for temporal joins
    2.17 +	List<TupleExpr> temporalJoins = new ArrayList<TupleExpr>();
    2.18 +
    2.19  	//
    2.20  	
    2.21  	public void setSelectQueryOptimizerFactory(GeneralDBSelectQueryOptimizerFactory factory) {
    2.22 @@ -112,13 +117,16 @@
    2.23  		new SameTermFilterOptimizer().optimize(expr, dataset, bindings);
    2.24  
    2.25  		//XXX
    2.26 -		//new SpatialJoinOptimizer().optimize(expr, dataset, bindings,spatialJoins);
    2.27 +		new SpatialJoinOptimizer().optimize(expr, dataset, bindings,spatialJoins);
    2.28 +		
    2.29 +		new TemporalJoinOptimizer().optimize(expr, dataset, bindings, temporalJoins);
    2.30  	}
    2.31  
    2.32  	protected void rdbmsOptimizations(TupleExpr expr, Dataset dataset, BindingSet bindings) {
    2.33  		new GeneralDBValueIdLookupOptimizer(vf).optimize(expr, dataset, bindings);
    2.34 -		factory.createRdbmsFilterOptimizer().optimize(expr, dataset, bindings,spatialJoins);
    2.35 +		factory.createRdbmsFilterOptimizer().optimize(expr, dataset, bindings,spatialJoins, temporalJoins);
    2.36  		this.spatialJoins.clear();
    2.37 +		this.temporalJoins.clear(); 
    2.38  		new GeneralDBVarColumnLookupOptimizer().optimize(expr, dataset, bindings);
    2.39  		GeneralDBValueJoinOptimizer valueJoins = new GeneralDBValueJoinOptimizer();
    2.40  		valueJoins.setBnodeTable(bnodes);
     3.1 --- a/generaldb/src/main/java/org/openrdf/sail/generaldb/optimizers/GeneralDBSelectQueryOptimizer.java	Thu May 09 14:46:55 2013 +0300
     3.2 +++ b/generaldb/src/main/java/org/openrdf/sail/generaldb/optimizers/GeneralDBSelectQueryOptimizer.java	Fri May 10 16:03:20 2013 +0300
     3.3 @@ -9,12 +9,15 @@
     3.4  import static org.openrdf.sail.generaldb.algebra.GeneralDBColumnVar.createObj;
     3.5  import static org.openrdf.sail.generaldb.algebra.GeneralDBColumnVar.createPred;
     3.6  import static org.openrdf.sail.generaldb.algebra.GeneralDBColumnVar.createSpatialColumn;
     3.7 +import static org.openrdf.sail.generaldb.algebra.GeneralDBColumnVar.createTemporalColumn;
     3.8  import static org.openrdf.sail.generaldb.algebra.GeneralDBColumnVar.createSubj;
     3.9  import static org.openrdf.sail.generaldb.algebra.base.GeneralDBExprSupport.coalesce;
    3.10  import static org.openrdf.sail.generaldb.algebra.base.GeneralDBExprSupport.eq;
    3.11  import static org.openrdf.sail.generaldb.algebra.base.GeneralDBExprSupport.isNull;
    3.12  import static org.openrdf.sail.generaldb.algebra.base.GeneralDBExprSupport.or;
    3.13  
    3.14 +import info.aduna.lang.service.ServiceRegistry;
    3.15 +
    3.16  import java.sql.SQLException;
    3.17  import java.util.ArrayList;
    3.18  import java.util.HashMap;
    3.19 @@ -157,6 +160,8 @@
    3.20  	private GeneralDBColumnVar previousTemporalArg = null;
    3.21  	private GeneralDBColumnVar previousTemporalAlias;
    3.22  
    3.23 +	private List<Var> existingTemporalJoins = new ArrayList<Var>();
    3.24 +
    3.25  
    3.26  	/**
    3.27  	 * 
    3.28 @@ -178,6 +183,8 @@
    3.29  
    3.30  	private IdSequence ids;
    3.31  
    3.32 +	private List<TupleExpr> temporalJoins;
    3.33 +
    3.34  	public void setSqlExprFactory(GeneralDBSqlExprFactory sql) {
    3.35  		this.sql = sql;
    3.36  	}
    3.37 @@ -194,10 +201,11 @@
    3.38  		this.ids = ids;
    3.39  	}
    3.40  
    3.41 -	public void optimize(TupleExpr tupleExpr, Dataset dataset, BindingSet bindings, List<TupleExpr> spatialJoins) {
    3.42 +	public void optimize(TupleExpr tupleExpr, Dataset dataset, BindingSet bindings, List<TupleExpr> spatialJoins, List<TupleExpr> temporalJoins) {
    3.43  		this.dataset = dataset;
    3.44  		this.bindings = bindings;
    3.45  		this.spatialJoins = spatialJoins;
    3.46 +		this.temporalJoins = temporalJoins;
    3.47  		tupleExpr.visit(this);
    3.48  	}
    3.49  
    3.50 @@ -593,6 +601,28 @@
    3.51  							break;
    3.52  							//							}
    3.53  						}
    3.54 +						else if(var.getName().equals(previousAlias.getName()))
    3.55 +						{
    3.56 +							existingSpatialJoins.add(var);
    3.57 +							queries[count] = new GeneralDBSelectQuery();
    3.58 +							Value objValue = getVarValue(var,bindings);
    3.59 +
    3.60 +							//any changes in these two lines could cause problems
    3.61 +							GeneralDBColumnVar colVar = createSpatialColumn("l_"+var.getName(), var, objValue);
    3.62 +							GeneralDBJoinItem from = new GeneralDBJoinItem("l_"+var.getName(), "geo_values");
    3.63 +
    3.64 +							queries[count].setFrom(from);
    3.65 +
    3.66 +							//assuming that only one var will reach this case
    3.67 +							from.addFilter(new GeneralDBSqlEq(new GeneralDBIdColumn(colVar), new GeneralDBIdColumn(previousAlias)));
    3.68 +
    3.69 +							//Copying functionality from meet(StatementPattern)
    3.70 +							GeneralDBSelectProjection proj = new GeneralDBSelectProjection();
    3.71 +							proj.setVar(colVar);
    3.72 +							proj.setId(new GeneralDBRefIdColumn(var));
    3.73 +							break;
    3.74 +							//							}
    3.75 +						}
    3.76  						count++;
    3.77  					}
    3.78  					mark = (count+1)%2;
    3.79 @@ -726,6 +756,140 @@
    3.80  				//node.replaceWith(queries[j]);
    3.81  
    3.82  			}
    3.83 +			else if(st.getSubjectVar().getName().equals("-dummy-temporal"))
    3.84 +			{
    3.85 +
    3.86 +				//Spatial join
    3.87 +
    3.88 +				//				List<Var> allVars = retrieveVars(node.getCondition());
    3.89 +				List<Var> allVars = new ArrayList<Var>(retrieveVars(node.getCondition()));
    3.90 +				GeneralDBSelectQuery queries[] = new GeneralDBSelectQuery[allVars.size()];
    3.91 +
    3.92 +				int count = 0;
    3.93 +
    3.94 +				//will probably be TWO contents at most in all cases concerning spatial filters here - have to make sure of that
    3.95 +				//Don't know which one of the spatial variables is bound with the upper join! Therefore, I altered the code to check 
    3.96 +				//for the possibility any of them is the one.
    3.97 +				int mark = 0;
    3.98 +				//FIXME remove the list after consulting Kostis for certainty, and replace with table[2]
    3.99 +				if(allVars.size()>1)
   3.100 +				{
   3.101 +					for(Var var : allVars)
   3.102 +					{
   3.103 +						if(var.getName().equals(previousTemporalAlias.getName()))
   3.104 +						{
   3.105 +
   3.106 +							//							if(var.getName().endsWith("?-buffer-"))
   3.107 +							//							{
   3.108 +							//								bufferCase = true;
   3.109 +							//								fixVarName(var);
   3.110 +							//								
   3.111 +							//								existingSpatialJoins.add(var);
   3.112 +							//								queries[count] = new GeneralDBSelectQuery();
   3.113 +							//								Value objValue = getVarValue(var,bindings);
   3.114 +							//								
   3.115 +							//								GeneralDBColumnVar colVar = createObj("l_"+var.getName(), var, objValue);
   3.116 +
   3.117 +
   3.118 +							//							}
   3.119 +							//							else //DEFAULT CASE. The only case differentiating from this one is buffer(?spatialVar,?thematicVar)
   3.120 +							//							{
   3.121 +
   3.122 +							existingTemporalJoins.add(var);
   3.123 +							queries[count] = new GeneralDBSelectQuery();
   3.124 +							Value objValue = getVarValue(var,bindings);
   3.125 +
   3.126 +							//any changes in these two lines could cause problems
   3.127 +							GeneralDBColumnVar colVar = createSpatialColumn("l_"+var.getName(), var, objValue);
   3.128 +							GeneralDBJoinItem from = new GeneralDBJoinItem("l_"+var.getName(), "period_values");
   3.129 +
   3.130 +							queries[count].setFrom(from);
   3.131 +
   3.132 +							//assuming that only one var will reach this case
   3.133 +							from.addFilter(new GeneralDBSqlEq(new GeneralDBIdColumn(colVar), new GeneralDBIdColumn(previousTemporalAlias)));
   3.134 +
   3.135 +							//Copying functionality from meet(StatementPattern)
   3.136 +							GeneralDBSelectProjection proj = new GeneralDBSelectProjection();
   3.137 +							proj.setVar(colVar);
   3.138 +							proj.setId(new GeneralDBRefIdColumn(var));
   3.139 +							break;
   3.140 +							//							}
   3.141 +						}
   3.142 +						else if(var.getName().equals(previousTemporalAlias.getName()))
   3.143 +						{
   3.144 +							existingTemporalJoins.add(var);
   3.145 +							queries[count] = new GeneralDBSelectQuery();
   3.146 +							Value objValue = getVarValue(var,bindings);
   3.147 +
   3.148 +							//any changes in these two lines could cause problems
   3.149 +							GeneralDBColumnVar colVar = createTemporalColumn("l_"+var.getName(), var, objValue);
   3.150 +							GeneralDBJoinItem from = new GeneralDBJoinItem("l_"+var.getName(), "period_values");
   3.151 +
   3.152 +							queries[count].setFrom(from);
   3.153 +
   3.154 +							//assuming that only one var will reach this case
   3.155 +							from.addFilter(new GeneralDBSqlEq(new GeneralDBIdColumn(colVar), new GeneralDBIdColumn(previousTemporalAlias)));
   3.156 +
   3.157 +							//Copying functionality from meet(StatementPattern)
   3.158 +							GeneralDBSelectProjection proj = new GeneralDBSelectProjection();
   3.159 +							proj.setVar(colVar);
   3.160 +							proj.setId(new GeneralDBRefIdColumn(var));
   3.161 +							break;
   3.162 +							//							}
   3.163 +						}
   3.164 +						count++;
   3.165 +					}
   3.166 +					mark = (count+1)%2;
   3.167 +				}
   3.168 +				//The second var of the spatial join -> must incorporate the spatial filter here
   3.169 +
   3.170 +
   3.171 +				Var var = allVars.get(mark);
   3.172 +				existingTemporalJoins.add(var);
   3.173 +				queries[mark] = new GeneralDBSelectQuery();
   3.174 +				Value objValue = getVarValue(var,bindings);
   3.175 +
   3.176 +				//any changes in these two lines could cause problems
   3.177 +				GeneralDBColumnVar colVar = createTemporalColumn("l_"+var.getName(), var, objValue);
   3.178 +				GeneralDBJoinItem from = new GeneralDBJoinItem("l_"+var.getName(), "period_values");
   3.179 +				queries[mark].setFrom(from);
   3.180 +
   3.181 +				previousTemporalArg = colVar;
   3.182 +
   3.183 +
   3.184 +				super.meet(node);
   3.185 +
   3.186 +
   3.187 +				//Incorporating temporal filter
   3.188 +				ValueExpr condition = null;
   3.189 +				for (ValueExpr expr : flatten(node.getCondition())) 
   3.190 +				{
   3.191 +					try 
   3.192 +					{
   3.193 +						GeneralDBSqlExpr sqlFilter = sql.createBooleanExpr(expr);
   3.194 +
   3.195 +						queries[mark].addFilter(sqlFilter);
   3.196 +					}
   3.197 +					catch (UnsupportedRdbmsOperatorException e)
   3.198 +					{
   3.199 +						if (condition == null) 
   3.200 +						{
   3.201 +							condition = expr;
   3.202 +						}
   3.203 +						else 
   3.204 +						{
   3.205 +							condition = new And(condition, expr);
   3.206 +						}
   3.207 +					}
   3.208 +				}
   3.209 +
   3.210 +				queries[count].setParentNode(node.getParentNode());
   3.211 +
   3.212 +				node.replaceWith(queries[mark]);
   3.213 +			
   3.214 +
   3.215 +			
   3.216 +			}
   3.217  			else
   3.218  			{
   3.219  				super.meet(node);
   3.220 @@ -800,6 +964,15 @@
   3.221  					break;
   3.222  				}
   3.223  			}
   3.224 +			for(TupleExpr sfilter : this.temporalJoins)
   3.225 +			{
   3.226 +				ValueExpr tmpExpr = ((Filter)sfilter).getCondition();
   3.227 +				if(tmpExpr.equals(dupFunctionCall))
   3.228 +				{
   3.229 +				dup = true;
   3.230 +					break;
   3.231 +				}
   3.232 +			}
   3.233  
   3.234  			super.meet(node);
   3.235  			if (node.getArg() instanceof GeneralDBSelectQuery) {
   3.236 @@ -1676,7 +1849,7 @@
   3.237  				{
   3.238  					//if(!((FunctionCall)expr).getURI().equals("http://strdf.di.uoa.gr/ontology#buffer") || argNo!=2 )
   3.239  					//{
   3.240 -					if(!existingSpatialJoins.contains(arg))
   3.241 +					if(!existingSpatialJoins.contains(arg) && !existingTemporalJoins.contains(arg))
   3.242  					{
   3.243  						//XXX note: this may cause error if the user intends to 
   3.244  						//perform an operation such as ?GEO1 ~ ?GEO1. 
   3.245 @@ -1700,7 +1873,7 @@
   3.246  		}
   3.247  		else if(expr instanceof Var)
   3.248  		{
   3.249 -			if(!existingSpatialJoins.contains(expr))
   3.250 +			if(!existingSpatialJoins.contains(expr) && !existingTemporalJoins.contains(expr))
   3.251  			{
   3.252  				//Want to find the UNIQUE names!
   3.253  				//if(!vars.contains(expr))
     4.1 --- a/runtime/src/test/resources/temporal-periods.nq	Thu May 09 14:46:55 2013 +0300
     4.2 +++ b/runtime/src/test/resources/temporal-periods.nq	Fri May 10 16:03:20 2013 +0300
     4.3 @@ -5,7 +5,7 @@
     4.4  <http://example.org/item2> <http://example.org/value> "20"^^<http://www.w3.org/2001/XMLSchema#int> "[2012-11-19T12:41:00,2012-11-19T13:41:00]"^^<http://strdf.di.uoa.gr/ontology#period>.
     4.5  <http://example.org/item1> <http://teleios.di.uoa.gr/ontologies/noaOntology.owl#hasGeometry> "POINT(1 0)"^^<http://strdf.di.uoa.gr/ontology#WKT> "[2012-11-19T12:41:00+02,2012-11-19T13:41:00]"^^<http://strdf.di.uoa.gr/ontology#period>.
     4.6  <http://example.org/item2> <http://teleios.di.uoa.gr/ontologies/noaOntology.owl#hasGeometry> "POINT(2 0)"^^<http://strdf.di.uoa.gr/ontology#WKT> "[2012-11-19T12:41:00+02,2012-11-19T13:41:00]"^^<http://strdf.di.uoa.gr/ontology#period>.
     4.7 -<http://example.org/item3> <http://teleios.di.uoa.gr/ontologies/noaOntology.owl#hasGeometry> "POINT(3 0)"^^<http://strdf.di.uoa.gr/ontology#WKT> "[2012-11-19t12:41:00+02,2012-11-19T13:41:00]"^^<http://strdf.di.uoa.gr/ontology#period>.
     4.8 +<http://example.org/item3> <http://teleios.di.uoa.gr/ontologies/noaOntology.owl#hasGeometry> "POINT(3 0)"^^<http://strdf.di.uoa.gr/ontology#WKT> "[2012-11-19T12:41:00+02,2012-11-19T13:41:00]"^^<http://strdf.di.uoa.gr/ontology#period>.
     4.9  <http://example.org/item1> <http://example.org/value> "10"^^<http://www.w3.org/2001/XMLSchema#int> "[2012-11-19T10:41:00,2012-11-19T11:41:00]"^^<http://strdf.di.uoa.gr/ontology#period>.
    4.10  <http://example.org/item2> <http://example.org/value> "20"^^<http://www.w3.org/2001/XMLSchema#int> "[2012-11-19T10:41:00,2012-11-19T15:41:00]"^^<http://strdf.di.uoa.gr/ontology#period>.
    4.11  <http://example.org/item4> <http://example.org/value> "20"^^<http://www.w3.org/2001/XMLSchema#int> "2012-01-19T10:41:00"^^<http://www.w3.org/2001/XMLSchema#dateTime> .