Disposable.

4 files changed, 738 insertions, 633 deletions

diff --git a/src/uk/ac/ox/cs/pagoda/query/AnswerTuple.java b/src/uk/ac/ox/cs/pagoda/query/AnswerTuple.java
index cb2b0a3..78aced1 100644
--- a/src/uk/ac/ox/cs/pagoda/query/AnswerTuple.java
+++ b/src/uk/ac/ox/cs/pagoda/query/AnswerTuple.java
@@ -172,7 +172,7 @@ public class AnswerTuple {
                                                 String lexicalForm = matcher.group("lexicalForm");
                                                 String dataTypeIRI = matcher.group("dataType");
                                                 Datatype dataType;
-                                                if (dataTypeIRI.isEmpty()) dataType = Datatype.RDF_PLAIN_LITERAL;
+                                                if(dataTypeIRI == null || dataTypeIRI.isEmpty()) dataType = Datatype.RDF_PLAIN_LITERAL;
                                                 else dataType = uk.ac.ox.cs.JRDFox.model.Datatype.value(dataTypeIRI);
                                                 terms[i] = uk.ac.ox.cs.JRDFox.model.Literal.create(lexicalForm, dataType);
                                         }
diff --git a/src/uk/ac/ox/cs/pagoda/query/AnswerTuples.java b/src/uk/ac/ox/cs/pagoda/query/AnswerTuples.java
index e1e5302..81efed0 100644
--- a/src/uk/ac/ox/cs/pagoda/query/AnswerTuples.java
+++ b/src/uk/ac/ox/cs/pagoda/query/AnswerTuples.java
@@ -1,23 +1,22 @@
 package uk.ac.ox.cs.pagoda.query;
 
-public interface AnswerTuples {
-        
-        public void reset(); 
-        
-        public boolean isValid();
-        
-        public int getArity();  
-        
-        public String[] getAnswerVariables(); 
-        
-        public void moveNext(); 
-        
-        public void dispose(); 
-        
-        public AnswerTuple getTuple(); 
-        
-        public boolean contains(AnswerTuple t);
-        
-        public void remove(); 
+import uk.ac.ox.cs.pagoda.util.disposable.Disposable;
 
+public abstract class AnswerTuples extends Disposable {
+
+    public abstract void reset();
+
+    public abstract boolean isValid();
+
+    public abstract int getArity();
+
+    public abstract String[] getAnswerVariables();
+
+    public abstract void moveNext();
+
+    public abstract AnswerTuple getTuple();
+
+    public abstract boolean contains(AnswerTuple t);
+
+    public abstract void remove();
 }
diff --git a/src/uk/ac/ox/cs/pagoda/query/AnswerTuplesImp.java b/src/uk/ac/ox/cs/pagoda/query/AnswerTuplesImp.java
index 3e0f320..fd3fb1f 100644
--- a/src/uk/ac/ox/cs/pagoda/query/AnswerTuplesImp.java
+++ b/src/uk/ac/ox/cs/pagoda/query/AnswerTuplesImp.java
@@ -3,7 +3,7 @@ package uk.ac.ox.cs.pagoda.query;
 import java.util.Iterator;
 import java.util.Set;
 
-public class AnswerTuplesImp implements AnswerTuples {
+public class AnswerTuplesImp extends AnswerTuples {
 
         int m_index; 
         Iterator<AnswerTuple> m_iter;
@@ -54,9 +54,6 @@ public class AnswerTuplesImp implements AnswerTuples {
         }
 
         @Override
-        public void dispose() {}
-
-        @Override
         public void reset() {
                 if (m_answers1 == null || m_answers1.isEmpty()) {
                         m_index = 2;
diff --git a/src/uk/ac/ox/cs/pagoda/query/QueryRecord.java b/src/uk/ac/ox/cs/pagoda/query/QueryRecord.java
index 1f81a78..742b7da 100644
--- a/src/uk/ac/ox/cs/pagoda/query/QueryRecord.java
+++ b/src/uk/ac/ox/cs/pagoda/query/QueryRecord.java
@@ -11,6 +11,8 @@ import uk.ac.ox.cs.pagoda.util.ConjunctiveQueryHelper;
 import uk.ac.ox.cs.pagoda.util.Namespace;
 import uk.ac.ox.cs.pagoda.util.PagodaProperties;
 import uk.ac.ox.cs.pagoda.util.Utility;
+import uk.ac.ox.cs.pagoda.util.disposable.Disposable;
+import uk.ac.ox.cs.pagoda.util.disposable.DisposedException;
 import uk.ac.ox.cs.pagoda.util.tuples.Tuple;
 import uk.ac.ox.cs.pagoda.util.tuples.TupleBuilder;
 
@@ -18,162 +20,180 @@ import java.io.*;
 import java.lang.reflect.Type;
 import java.util.*;
 
-public class QueryRecord {
-        
-        public static final String botQueryText = "SELECT ?X WHERE { ?X <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2002/07/owl#Nothing> }";
-        public static final String SEPARATOR = "----------------------------------------";
-        private static final String RDF_TYPE = "a"; //"rdf:type"; //RDF.type.toString();
-        boolean processed = false;
-        String stringQueryID = null;
-        OWLOntology relevantOntology = null;
-        Set<DLClause> relevantClauses = new HashSet<DLClause>();
-        double[] timer;
-        int subID;
-        DLClause queryClause = null;
-        int queryID = -1;
-        Set<AnswerTuple> soundAnswerTuples = new HashSet<AnswerTuple>();
-        private Step difficulty;
-        private String queryText;
-        private String[][] answerVariables = null;
-        private Set<AnswerTuple> gapAnswerTuples = null;
-        private QueryManager m_manager;
-
-        private QueryRecord() {
-        }
+public class QueryRecord extends Disposable {
+
+    public static final String botQueryText =
+            "SELECT ?X WHERE { ?X <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2002/07/owl#Nothing> }";
+    public static final String SEPARATOR = "----------------------------------------";
+    private static final String RDF_TYPE = "a"; //"rdf:type"; //RDF.type.toString();
+    boolean processed = false;
+    String stringQueryID = null;
+    OWLOntology relevantOntology = null;
+    Set<DLClause> relevantClauses = new HashSet<DLClause>();
+    double[] timer;
+    int subID;
+    DLClause queryClause = null;
+    int queryID = -1;
+    Set<AnswerTuple> soundAnswerTuples = new HashSet<AnswerTuple>();
+    private Step difficulty;
+    private String queryText;
+    private String[][] answerVariables = null;
+    private Set<AnswerTuple> gapAnswerTuples = null;
+    private QueryManager m_manager;
+
+    private QueryRecord() {
+    }
 
 //      private boolean containsAuxPredicate(String str) {
 //              return  str.contains(Namespace.PAGODA_AUX) || str.contains("_AUX") || str.contains("owl#Nothing") ||
 //                              str.contains("internal:def"); 
 //      }
 
-        public QueryRecord(QueryManager manager, String text, int id, int subID) {
-                m_manager = manager;
-                resetInfo(text, id, subID);
-                resetTimer();
-        }
-
-        public static Collection<String> collectQueryTexts(Collection<QueryRecord> queryRecords) {
-                Collection<String> texts = new LinkedList<String>();
-                for(QueryRecord record : queryRecords)
-                        texts.add(record.queryText);
-                return texts;
-        }
-
-        public void resetInfo(String text, int id, int subid) {
-                queryID = id;
-                subID = subid;
-                stringQueryID = id + (subID == 0 ? "" : "_" + subID);
-                m_manager.remove(queryText);
-                m_manager.put(text, this);
-                queryClause = null;
-                answerVariables = ConjunctiveQueryHelper.getAnswerVariables(text);
-                queryText = text; // .replace("_:", "?");
-        }
-
-        public void resetTimer() {
-                int length = Step.values().length;
-                timer = new double[length];
-                for(int i = 0; i < length; ++i) timer[i] = 0;
-        }
-
-        public AnswerTuples getAnswers() {
-                if(isProcessed())
-                        return getLowerBoundAnswers();
-
-                return getUpperBoundAnswers();
-        }
-
-        public AnswerTuples getLowerBoundAnswers() {
-                return new AnswerTuplesImp(answerVariables[0], soundAnswerTuples);
-        }
-
-        public AnswerTuples getUpperBoundAnswers() {
-                return new AnswerTuplesImp(answerVariables[0], soundAnswerTuples, gapAnswerTuples);
-        }
-
-        public boolean updateLowerBoundAnswers(AnswerTuples answerTuples) {
-                if(answerTuples == null) return false;
-                boolean update = false;
-                for(AnswerTuple tuple; answerTuples.isValid(); answerTuples.moveNext()) {
-                        tuple = answerTuples.getTuple();
-                        if(!soundAnswerTuples.contains(tuple) && (gapAnswerTuples == null || gapAnswerTuples.contains(tuple))) {
-                                soundAnswerTuples.add(tuple);
-                                if(gapAnswerTuples != null)
-                                        gapAnswerTuples.remove(tuple);
-                                update = true;
-                        }
-                }
-
-                if(soundAnswerTuples.isEmpty())
-                        Utility.logInfo("Lower bound answers empty");
-                else if(update)
-                        Utility.logInfo("Lower bound answers updated: " + soundAnswerTuples.size());
-                else
-                        Utility.logInfo("Lower bound answers unchanged");
-
-                return update;
-        }
-
-        public boolean updateUpperBoundAnswers(AnswerTuples answerTuples) {
-                return updateUpperBoundAnswers(answerTuples, false);
-        }
-
-        public boolean updateUpperBoundAnswers(AnswerTuples answerTuples, boolean toCheckAux) {
-                if(!(answerTuples instanceof RDFoxAnswerTuples)) {
-                        String msg = "The upper bound must be computed by RDFox!";
-                        Utility.logError(msg);
-                        throw new IllegalArgumentException(msg);
-                }
-
-                RDFoxAnswerTuples rdfoxAnswerTuples = (RDFoxAnswerTuples) answerTuples;
-
-                Set<AnswerTuple> candidateGapAnswerTuples = new HashSet<AnswerTuple>();
-                AnswerTuple tuple;
-                for(; rdfoxAnswerTuples.isValid(); rdfoxAnswerTuples.moveNext()) {
-                        tuple = rdfoxAnswerTuples.getTuple();
-                        if(isBottom() || !tuple.hasAnonymousIndividual())
-                                if((!toCheckAux || !tuple.hasAuxPredicate()) && !soundAnswerTuples.contains(tuple))
-                                        candidateGapAnswerTuples.add(tuple);
-                }
-
-                /*** START: debugging ***/
-                if(PagodaProperties.isDebuggingMode()) {
-                        if(rdfoxAnswerTuples.getArity() != getAnswerVariables().length)
-                                throw new IllegalArgumentException(
-                                                "The arity of answers (" + rdfoxAnswerTuples.getArity() + ") " +
-                                                                "is different from the number of answer variables (" +
-                                                                getAnswerVariables().length + ")");
-
-                        Set<AnswerTuple> namedAnswerTuples = new HashSet<>();
-                        rdfoxAnswerTuples.reset();
-                        for(; rdfoxAnswerTuples.isValid(); rdfoxAnswerTuples.moveNext()) {
-                                tuple = rdfoxAnswerTuples.getTuple();
+    public QueryRecord(QueryManager manager, String text, int id, int subID) {
+        m_manager = manager;
+        resetInfo(text, id, subID);
+        resetTimer();
+    }
+
+    public static Collection<String> collectQueryTexts(Collection<QueryRecord> queryRecords) {
+        Collection<String> texts = new LinkedList<String>();
+        for(QueryRecord record : queryRecords)
+            texts.add(record.queryText);
+        return texts;
+    }
+
+    public void resetInfo(String text, int id, int subid) {
+        if(isDisposed()) throw new DisposedException();
+
+        queryID = id;
+        subID = subid;
+        stringQueryID = id + (subID == 0 ? "" : "_" + subID);
+        m_manager.remove(queryText);
+        m_manager.put(text, this);
+        queryClause = null;
+        answerVariables = ConjunctiveQueryHelper.getAnswerVariables(text);
+        queryText = text; // .replace("_:", "?");
+    }
+
+    public void resetTimer() {
+        if(isDisposed()) throw new DisposedException();
+
+        int length = Step.values().length;
+        timer = new double[length];
+        for(int i = 0; i < length; ++i) timer[i] = 0;
+    }
+
+    public AnswerTuples getAnswers() {
+        if(isDisposed()) throw new DisposedException();
+
+        if(isProcessed())
+            return getLowerBoundAnswers();
+
+        return getUpperBoundAnswers();
+    }
+
+    public AnswerTuples getLowerBoundAnswers() {
+        if(isDisposed()) throw new DisposedException();
+
+        return new AnswerTuplesImp(answerVariables[0], soundAnswerTuples);
+    }
+
+    public AnswerTuples getUpperBoundAnswers() {
+        if(isDisposed()) throw new DisposedException();
+
+        return new AnswerTuplesImp(answerVariables[0], soundAnswerTuples, gapAnswerTuples);
+    }
+
+    public boolean updateLowerBoundAnswers(AnswerTuples answerTuples) {
+        if(isDisposed()) throw new DisposedException();
+
+        if(answerTuples == null) return false;
+        boolean update = false;
+        for(AnswerTuple tuple; answerTuples.isValid(); answerTuples.moveNext()) {
+            tuple = answerTuples.getTuple();
+            if(!soundAnswerTuples.contains(tuple) && (gapAnswerTuples == null || gapAnswerTuples.contains(tuple))) {
+                soundAnswerTuples.add(tuple);
+                if(gapAnswerTuples != null)
+                    gapAnswerTuples.remove(tuple);
+                update = true;
+            }
+        }
+
+        if(soundAnswerTuples.isEmpty())
+            Utility.logInfo("Lower bound answers empty");
+        else if(update)
+            Utility.logInfo("Lower bound answers updated: " + soundAnswerTuples.size());
+        else
+            Utility.logInfo("Lower bound answers unchanged");
+
+        return update;
+    }
+
+    public boolean updateUpperBoundAnswers(AnswerTuples answerTuples) {
+        if(isDisposed()) throw new DisposedException();
+
+        return updateUpperBoundAnswers(answerTuples, false);
+    }
+
+    public boolean updateUpperBoundAnswers(AnswerTuples answerTuples, boolean toCheckAux) {
+        if(isDisposed()) throw new DisposedException();
+
+        if(!(answerTuples instanceof RDFoxAnswerTuples)) {
+            String msg = "The upper bound must be computed by RDFox!";
+            Utility.logError(msg);
+            throw new IllegalArgumentException(msg);
+        }
+
+        RDFoxAnswerTuples rdfoxAnswerTuples = (RDFoxAnswerTuples) answerTuples;
+
+        Set<AnswerTuple> candidateGapAnswerTuples = new HashSet<AnswerTuple>();
+        AnswerTuple tuple;
+        for(; rdfoxAnswerTuples.isValid(); rdfoxAnswerTuples.moveNext()) {
+            tuple = rdfoxAnswerTuples.getTuple();
+            if(isBottom() || !tuple.hasAnonymousIndividual())
+                if((!toCheckAux || !tuple.hasAuxPredicate()) && !soundAnswerTuples.contains(tuple))
+                    candidateGapAnswerTuples.add(tuple);
+        }
+
+        /*** START: debugging ***/
+        if(PagodaProperties.isDebuggingMode()) {
+            if(rdfoxAnswerTuples.getArity() != getAnswerVariables().length)
+                throw new IllegalArgumentException(
+                        "The arity of answers (" + rdfoxAnswerTuples.getArity() + ") " +
+                                "is different from the number of answer variables (" +
+                                getAnswerVariables().length + ")");
+
+            Set<AnswerTuple> namedAnswerTuples = new HashSet<>();
+            rdfoxAnswerTuples.reset();
+            for(; rdfoxAnswerTuples.isValid(); rdfoxAnswerTuples.moveNext()) {
+                tuple = rdfoxAnswerTuples.getTuple();
 //                              if(isBottom() || !tuple.hasAnonymousIndividual()) {
-                                namedAnswerTuples.add(tuple);
+                namedAnswerTuples.add(tuple);
 //                              }
-                        }
-                        HashSet<AnswerTuple> difference = new HashSet<>(soundAnswerTuples);
-                        difference.removeAll(namedAnswerTuples);
-                        if(!difference.isEmpty())
-                                throw new IllegalArgumentException("The upper bound does not contain the lower bound! Missing answers: " + difference
-                                                .size());
-                }
-                /*** END: debugging ***/
-
-                boolean update;
-                if(gapAnswerTuples == null) {
-                        gapAnswerTuples = candidateGapAnswerTuples;
-                        update = true;
-                } else {
-                        update = gapAnswerTuples.retainAll(candidateGapAnswerTuples);
-                }
-
-                if(update)
-                        Utility.logInfo("Upper bound answers updated: " + getNumberOfAnswers());
-                else
-                        Utility.logInfo("Upper bound answers unchanged");
-
-                return update;
+            }
+            HashSet<AnswerTuple> difference = new HashSet<>(soundAnswerTuples);
+            difference.removeAll(namedAnswerTuples);
+            if(!difference.isEmpty())
+                throw new IllegalArgumentException("The upper bound does not contain the lower bound! Missing answers: " + difference
+                        .size());
+        }
+        /*** END: debugging ***/
+
+        boolean update;
+        if(gapAnswerTuples == null) {
+            gapAnswerTuples = candidateGapAnswerTuples;
+            update = true;
+        }
+        else {
+            update = gapAnswerTuples.retainAll(candidateGapAnswerTuples);
+        }
+
+        if(update)
+            Utility.logInfo("Upper bound answers updated: " + getNumberOfAnswers());
+        else
+            Utility.logInfo("Upper bound answers unchanged");
+
+        return update;
 
 //              boolean update = false;
 //              for(Iterator<AnswerTuple> iter = gapAnswerTuples.iterator(); iter.hasNext(); ) {
@@ -183,96 +203,116 @@ public class QueryRecord {
 //                              update = true;
 //                      }
 //              }
-        }
-
-        public int getNumberOfAnswers() {
-                return soundAnswerTuples.size() + gapAnswerTuples.size();
-        }
-
-        public void markAsProcessed() {
-                processed = true;
-        }
-
-        public boolean isProcessed() {
-                if(gapAnswerTuples != null && gapAnswerTuples.isEmpty()) processed = true;
-                return processed;
-        }
-
-        public String[] getDistinguishedVariables() {
-                return answerVariables[1];
-        }
-
-        public String[] getAnswerVariables() {
-                return answerVariables[0];
-        }
-
-        public String[][] getVariables() {
-                return answerVariables;
-        }
-        
-        public String getQueryText() {
-                return queryText;
-        }
-        
-        public String getQueryID() {
-                return stringQueryID;
-        }
-
-        public AnswerTuples getGapAnswers() {
-                return new AnswerTuplesImp(answerVariables[0], gapAnswerTuples);
-        }
-
-        public String toString() {
-                return queryText;
-        }
-
-        public void outputAnswers(BufferedWriter writer) throws IOException {
-
-                int answerCounter = soundAnswerTuples.size();
-                if(!isProcessed()) answerCounter += gapAnswerTuples.size();
-
-                Utility.logInfo("The number of answer tuples: " + answerCounter);
-
-                if (writer != null) {
-                        writer.write("-------------- Query " + queryID + " ---------------------");
-                        writer.newLine();
-                        writer.write(queryText);
-                        writer.newLine();
-                        StringBuilder space = new StringBuilder();
-                        int arity = getArity(), varSpace = 0;
-                        for (int i = 0; i < arity; ++i)
-                                varSpace += answerVariables[0][i].length();
-                        for (int i = 0; i < (SEPARATOR.length() - varSpace) / (arity + 1); ++i)
-                                space.append(" ");
-                        for (int i = 0; i < getArity(); ++i) {
-                                writer.write(space.toString());
-                                writer.write(answerVariables[0][i]);
-                        }
-                        writer.newLine();
-                        writer.write(SEPARATOR);
-                        writer.newLine();
-                        for (AnswerTuple tuple: soundAnswerTuples) {
-                                writer.write(tuple.toString());
-                                writer.newLine();
-                        }
-                        if(!isProcessed())
-                                for (AnswerTuple tuple: gapAnswerTuples) {
-                                        writer.write("*");
-                                        writer.write(tuple.toString());
-                                        writer.newLine();
-                                }
+    }
+
+    public int getNumberOfAnswers() {
+        if(isDisposed()) throw new DisposedException();
+
+        return soundAnswerTuples.size() + gapAnswerTuples.size();
+    }
+
+    public void markAsProcessed() {
+        processed = true;
+    }
+
+    public boolean isProcessed() {
+        if(isDisposed()) throw new DisposedException();
+
+        if(gapAnswerTuples != null && gapAnswerTuples.isEmpty()) processed = true;
+        return processed;
+    }
+
+    public String[] getDistinguishedVariables() {
+        if(isDisposed()) throw new DisposedException();
+
+        return answerVariables[1];
+    }
+
+    public String[] getAnswerVariables() {
+        if(isDisposed()) throw new DisposedException();
+
+        return answerVariables[0];
+    }
+
+    public String[][] getVariables() {
+        if(isDisposed()) throw new DisposedException();
+
+        return answerVariables;
+    }
+
+    public String getQueryText() {
+        if(isDisposed()) throw new DisposedException();
+
+        return queryText;
+    }
+
+    public String getQueryID() {
+        if(isDisposed()) throw new DisposedException();
+
+        return stringQueryID;
+    }
+
+    public AnswerTuples getGapAnswers() {
+        if(isDisposed()) throw new DisposedException();
+
+        return new AnswerTuplesImp(answerVariables[0], gapAnswerTuples);
+    }
+
+    public String toString() {
+        if(isDisposed()) throw new DisposedException();
+
+        return queryText;
+    }
+
+    public void outputAnswers(BufferedWriter writer) throws IOException {
+        if(isDisposed()) throw new DisposedException();
+
+        int answerCounter = soundAnswerTuples.size();
+        if(!isProcessed()) answerCounter += gapAnswerTuples.size();
+
+        Utility.logInfo("The number of answer tuples: " + answerCounter);
+
+        if(writer != null) {
+            writer.write("-------------- Query " + queryID + " ---------------------");
+            writer.newLine();
+            writer.write(queryText);
+            writer.newLine();
+            StringBuilder space = new StringBuilder();
+            int arity = getArity(), varSpace = 0;
+            for(int i = 0; i < arity; ++i)
+                varSpace += answerVariables[0][i].length();
+            for(int i = 0; i < (SEPARATOR.length() - varSpace) / (arity + 1); ++i)
+                space.append(" ");
+            for(int i = 0; i < getArity(); ++i) {
+                writer.write(space.toString());
+                writer.write(answerVariables[0][i]);
+            }
+            writer.newLine();
+            writer.write(SEPARATOR);
+            writer.newLine();
+            for(AnswerTuple tuple : soundAnswerTuples) {
+                writer.write(tuple.toString());
+                writer.newLine();
+            }
+            if(!isProcessed())
+                for(AnswerTuple tuple : gapAnswerTuples) {
+                    writer.write("*");
+                    writer.write(tuple.toString());
+                    writer.newLine();
+                }
 //                      writer.write(SEPARATOR);
-                        writer.newLine();
-                }
+            writer.newLine();
+        }
 
-        }
+    }
 
-        public void outputAnswerStatistics() {
+    public void outputAnswerStatistics() {
+        if(isDisposed()) throw new DisposedException();
 
-                int answerCounter = soundAnswerTuples.size();
-                if(!isProcessed()) answerCounter += gapAnswerTuples.size();
+        int answerCounter = soundAnswerTuples.size();
+        if(!isProcessed()) answerCounter += gapAnswerTuples.size();
 
-                Utility.logInfo("The number of answer tuples: " + answerCounter);
+        Utility.logInfo("The number of answer tuples: " + answerCounter);
 //              if (jsonAnswers != null) {
 //                      JSONObject jsonAnswer = new JSONObject();
 //
@@ -297,407 +337,476 @@ public class QueryRecord {
 //
 //                      jsonAnswers.put(Integer.toString(queryID), jsonAnswer);
 //              }
-        }
-
-        public void outputTimes() {
-                for (Step step: Step.values()) {
-                        Utility.logDebug("time for " + step + ": " + timer[step.ordinal()]);
-                }
-        }
-
-        public String outputSoundAnswerTuple() {
-                StringBuilder builder = new StringBuilder();
-                for (AnswerTuple tuple: soundAnswerTuples)
-                        builder.append(tuple.toString()).append(Utility.LINE_SEPARATOR);
-                return builder.toString();
-        }
-
-        public String outputGapAnswerTuple() {
-                StringBuilder builder = new StringBuilder();
-                for(AnswerTuple tuple : gapAnswerTuples)
-                        builder.append(tuple.toString()).append(Utility.LINE_SEPARATOR);
-                return builder.toString();
-        }
-
-        public Step getDifficulty() {
-                return difficulty;
-        }
-
-        public void setDifficulty(Step step) {
-                this.difficulty = step;
-        }
-
-        public OWLOntology getRelevantOntology() {
-                return relevantOntology;
-        }
-
-        public void setRelevantOntology(OWLOntology knowledgebase) {
-                relevantOntology = knowledgebase;
-        }
-
-        public void saveRelevantOntology(String filename) {
-                if(relevantOntology == null) return;
-                OWLOntologyManager manager = relevantOntology.getOWLOntologyManager();
-                try {
-                        FileOutputStream outputStream = new FileOutputStream(filename);
-                        manager.saveOntology(relevantOntology, outputStream);
-                        outputStream.close();
-                } catch (OWLOntologyStorageException e) {
-                        e.printStackTrace();
-                } catch (FileNotFoundException e) {
-                        e.printStackTrace();
-                } catch (IOException e) {
-                        e.printStackTrace();
-                }
-        }
-
-        public void saveRelevantClause() {
-                if(relevantClauses == null) return;
-                GeneralProgram p = new GeneralProgram(relevantClauses, relevantOntology);
-                p.save();
-        }
-
-        public void removeUpperBoundAnswers(Collection<AnswerTuple> answers) {
-                for (AnswerTuple answer: answers) {
+    }
+
+    public void outputTimes() {
+        if(isDisposed()) throw new DisposedException();
+
+        for(Step step : Step.values()) {
+            Utility.logDebug("time for " + step + ": " + timer[step.ordinal()]);
+        }
+    }
+
+    public String outputSoundAnswerTuple() {
+        if(isDisposed()) throw new DisposedException();
+
+        StringBuilder builder = new StringBuilder();
+        for(AnswerTuple tuple : soundAnswerTuples)
+            builder.append(tuple.toString()).append(Utility.LINE_SEPARATOR);
+        return builder.toString();
+    }
+
+    public String outputGapAnswerTuple() {
+        if(isDisposed()) throw new DisposedException();
+
+        StringBuilder builder = new StringBuilder();
+        for(AnswerTuple tuple : gapAnswerTuples)
+            builder.append(tuple.toString()).append(Utility.LINE_SEPARATOR);
+        return builder.toString();
+    }
+
+    public Step getDifficulty() {
+        if(isDisposed()) throw new DisposedException();
+
+        return difficulty;
+    }
+
+    public void setDifficulty(Step step) {
+        if(isDisposed()) throw new DisposedException();
+
+        this.difficulty = step;
+    }
+
+    public OWLOntology getRelevantOntology() {
+        if(isDisposed()) throw new DisposedException();
+
+        return relevantOntology;
+    }
+
+    public void setRelevantOntology(OWLOntology knowledgebase) {
+        if(isDisposed()) throw new DisposedException();
+
+        relevantOntology = knowledgebase;
+    }
+
+    public void saveRelevantOntology(String filename) {
+        if(isDisposed()) throw new DisposedException();
+
+        if(relevantOntology == null) return;
+        OWLOntologyManager manager = relevantOntology.getOWLOntologyManager();
+        try {
+            FileOutputStream outputStream = new FileOutputStream(filename);
+            manager.saveOntology(relevantOntology, outputStream);
+            outputStream.close();
+        } catch(OWLOntologyStorageException e) {
+            e.printStackTrace();
+        } catch(FileNotFoundException e) {
+            e.printStackTrace();
+        } catch(IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+    public void saveRelevantClause() {
+        if(isDisposed()) throw new DisposedException();
+
+        if(relevantClauses == null) return;
+        GeneralProgram p = new GeneralProgram(relevantClauses, relevantOntology);
+        p.save();
+    }
+
+    public void removeUpperBoundAnswers(Collection<AnswerTuple> answers) {
+        if(isDisposed()) throw new DisposedException();
+
+        for(AnswerTuple answer : answers) {
 //                      if (soundAnswerTuples.contains(answer))
 //                              Utility.logError("The answer (" + answer + ") cannot be removed, because it is in the lower bound.");
-                        if (!gapAnswerTuples.contains(answer))
-                                Utility.logError("The answer (" + answer + ") cannot be removed, because it is not in the upper bound.");
-                        gapAnswerTuples.remove(answer);
-                }
-        }
-
-        public void addLowerBoundAnswers(Collection<AnswerTuple> answers) {
-                for (AnswerTuple answer: answers) {
-                        if (!gapAnswerTuples.contains(answer))
-                                Utility.logError("The answer (" + answer + ") cannot be added, because it is not in the upper bound.");
-                        gapAnswerTuples.remove(answer);
-
-                        answer = AnswerTuple.getInstance(answer, answerVariables[0].length);
+            if(!gapAnswerTuples.contains(answer))
+                Utility.logError("The answer (" + answer + ") cannot be removed, because it is not in the upper bound.");
+            gapAnswerTuples.remove(answer);
+        }
+    }
+
+    public void addLowerBoundAnswers(Collection<AnswerTuple> answers) {
+        if(isDisposed()) throw new DisposedException();
+
+        for(AnswerTuple answer : answers) {
+            if(!gapAnswerTuples.contains(answer))
+                Utility.logError("The answer (" + answer + ") cannot be added, because it is not in the upper bound.");
+            gapAnswerTuples.remove(answer);
+
+            answer = AnswerTuple.getInstance(answer, answerVariables[0].length);
 //                      if (soundAnswerTuples.contains(answer))
 //                              Utility.logError("The answer (" + answer + ") cannot be added, because it is in the lower bound.");
-                        soundAnswerTuples.add(answer);
-                }
-        }
-
-        public int getNoOfSoundAnswers() {
-                return soundAnswerTuples.size();
-        }
-
-        public void addProcessingTime(Step step, double time) {
-                timer[step.ordinal()] += time;
-        }
-
-        public int getArity() {
-                return answerVariables[0].length;
-        }
-
-        public void addRelevantClauses(DLClause clause) {
-                relevantClauses.add(clause);
-        }
-
-        public Set<DLClause> getRelevantClauses() {
-                return relevantClauses;
-        }
-
-        public void clearClauses() {
-                relevantClauses.clear();
-        }
-
-        public boolean isHorn() {
-                for (DLClause clause: relevantClauses)
-                        if (clause.getHeadLength() > 1)
-                                return false;
-                return true;
-        }
-
-        public void saveABoxInTurtle(String filename) {
-                try {
-                        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(filename)));
-                        OWLIndividual a, b;
-                        StringBuilder builder = new StringBuilder();
-                        for (OWLAxiom axiom: relevantOntology.getABoxAxioms(true)) {
-                                if (axiom instanceof OWLClassAssertionAxiom) {
-                                        OWLClassAssertionAxiom classAssertion = (OWLClassAssertionAxiom) axiom;
-                                        OWLClass c = (OWLClass) classAssertion.getClassExpression();
-                                        a = classAssertion.getIndividual();
-                                        builder.append(a.toString())
-                                                   .append(" <")
-                                                   .append(Namespace.RDF_TYPE)
-                                                   .append("> ")
-                                                   .append(c.toString());
-                                }
-                                else if (axiom instanceof OWLObjectPropertyAssertionAxiom) {
-                                        OWLObjectPropertyAssertionAxiom propertyAssertion = (OWLObjectPropertyAssertionAxiom) axiom;
-                                        OWLObjectProperty p = (OWLObjectProperty) propertyAssertion.getProperty();
-                                        a = propertyAssertion.getSubject();
-                                        b = propertyAssertion.getObject();
-                                        builder.append(a.toString()).append(" ").append(p.toString()).append(" ").append(b.toString());
-                                }
-                                else if (axiom instanceof OWLDataPropertyAssertionAxiom) {
-                                        OWLDataPropertyAssertionAxiom propertyAssertion = (OWLDataPropertyAssertionAxiom) axiom;
-                                        OWLDataProperty p = (OWLDataProperty) propertyAssertion.getProperty();
-                                        a = propertyAssertion.getSubject();
-                                        OWLLiteral l = propertyAssertion.getObject();
-                                        builder.append(a.toString()).append(" ").append(p.toString()).append(" ").append(l.toString());
-                                }
-
-                                writer.write(builder.toString());
-                                writer.write(" .");
-                                writer.newLine();
-                                builder.setLength(0);
-                        }
-                        writer.close();
-                } catch (IOException e) {
-                        e.printStackTrace();
-                } finally {
-
-                }
-        }
-        
-        public void updateSubID() {
-                ++subID;
-                stringQueryID = String.valueOf(queryID) + "_" + subID;
-        }
-
-        public DLClause getClause() {
-                if (queryClause != null)
-                        return queryClause;
-                return queryClause = DLClauseHelper.getQuery(queryText, null);
-        }
-
-        public boolean isBottom() {
-                return queryID == 0;
-        }
-
-        public int getNoOfCompleteAnswers() {
-                return soundAnswerTuples.size() + gapAnswerTuples.size();
-        }
-
-        public int getSubID() {
-                return subID;
-        }
-
-        public boolean hasSameGapAnswers(QueryRecord that) {
-                return gapAnswerTuples.containsAll(that.gapAnswerTuples) && that.gapAnswerTuples.containsAll(gapAnswerTuples);
-        }
-
-        public void dispose() {
-                m_manager.remove(queryText);
-                if(gapAnswerTuples != null) gapAnswerTuples = null;
-                if(soundAnswerTuples != null) soundAnswerTuples = null;
-                if (relevantClauses != null) relevantClauses.clear();
-                if (relevantOntology != null)
-                        relevantOntology.getOWLOntologyManager().removeOntology(relevantOntology);
-                answerVariables = null;
-        }
-
-        public boolean canBeEncodedIntoAtom() {
-                // FIXME
-                return true;
+            soundAnswerTuples.add(answer);
+        }
+    }
+
+    public int getNoOfSoundAnswers() {
+        if(isDisposed()) throw new DisposedException();
+
+        return soundAnswerTuples.size();
+    }
+
+    public void addProcessingTime(Step step, double time) {
+        if(isDisposed()) throw new DisposedException();
+
+        timer[step.ordinal()] += time;
+    }
+
+    public int getArity() {
+        if(isDisposed()) throw new DisposedException();
+
+        return answerVariables[0].length;
+    }
+
+    public void addRelevantClauses(DLClause clause) {
+        if(isDisposed()) throw new DisposedException();
+
+        relevantClauses.add(clause);
+    }
+
+    public Set<DLClause> getRelevantClauses() {
+        if(isDisposed()) throw new DisposedException();
+
+        return relevantClauses;
+    }
+
+    public void clearClauses() {
+        if(isDisposed()) throw new DisposedException();
+
+        relevantClauses.clear();
+    }
+
+    public boolean isHorn() {
+        if(isDisposed()) throw new DisposedException();
+
+        for(DLClause clause : relevantClauses)
+            if(clause.getHeadLength() > 1)
+                return false;
+        return true;
+    }
+
+    public void saveABoxInTurtle(String filename) {
+        if(isDisposed()) throw new DisposedException();
+
+        try {
+            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(filename)));
+            OWLIndividual a, b;
+            StringBuilder builder = new StringBuilder();
+            for(OWLAxiom axiom : relevantOntology.getABoxAxioms(true)) {
+                if(axiom instanceof OWLClassAssertionAxiom) {
+                    OWLClassAssertionAxiom classAssertion = (OWLClassAssertionAxiom) axiom;
+                    OWLClass c = (OWLClass) classAssertion.getClassExpression();
+                    a = classAssertion.getIndividual();
+                    builder.append(a.toString())
+                           .append(" <")
+                           .append(Namespace.RDF_TYPE)
+                           .append("> ")
+                           .append(c.toString());
+                }
+                else if(axiom instanceof OWLObjectPropertyAssertionAxiom) {
+                    OWLObjectPropertyAssertionAxiom propertyAssertion = (OWLObjectPropertyAssertionAxiom) axiom;
+                    OWLObjectProperty p = (OWLObjectProperty) propertyAssertion.getProperty();
+                    a = propertyAssertion.getSubject();
+                    b = propertyAssertion.getObject();
+                    builder.append(a.toString()).append(" ").append(p.toString()).append(" ").append(b.toString());
+                }
+                else if(axiom instanceof OWLDataPropertyAssertionAxiom) {
+                    OWLDataPropertyAssertionAxiom propertyAssertion = (OWLDataPropertyAssertionAxiom) axiom;
+                    OWLDataProperty p = (OWLDataProperty) propertyAssertion.getProperty();
+                    a = propertyAssertion.getSubject();
+                    OWLLiteral l = propertyAssertion.getObject();
+                    builder.append(a.toString()).append(" ").append(p.toString()).append(" ").append(l.toString());
+                }
+
+                writer.write(builder.toString());
+                writer.write(" .");
+                writer.newLine();
+                builder.setLength(0);
+            }
+            writer.close();
+        } catch(IOException e) {
+            e.printStackTrace();
+        } finally {
+
+        }
+    }
+
+    public void updateSubID() {
+        if(isDisposed()) throw new DisposedException();
+
+        ++subID;
+        stringQueryID = String.valueOf(queryID) + "_" + subID;
+    }
+
+    public DLClause getClause() {
+        if(isDisposed()) throw new DisposedException();
+
+        if(queryClause != null)
+            return queryClause;
+        return queryClause = DLClauseHelper.getQuery(queryText, null);
+    }
+
+    public boolean isBottom() {
+        if(isDisposed()) throw new DisposedException();
+
+        return queryID == 0;
+    }
+
+    public int getNoOfCompleteAnswers() {
+        if(isDisposed()) throw new DisposedException();
+
+        return soundAnswerTuples.size() + gapAnswerTuples.size();
+    }
+
+    public int getSubID() {
+        if(isDisposed()) throw new DisposedException();
+
+        return subID;
+    }
+
+    public boolean hasSameGapAnswers(QueryRecord that) {
+        if(isDisposed()) throw new DisposedException();
+
+        return gapAnswerTuples.containsAll(that.gapAnswerTuples) && that.gapAnswerTuples.containsAll(gapAnswerTuples);
+    }
+
+    @Override
+    public void dispose() {
+        super.dispose();
+        m_manager.remove(queryText);
+        if(gapAnswerTuples != null) gapAnswerTuples = null;
+        if(soundAnswerTuples != null) soundAnswerTuples = null;
+        if(relevantClauses != null) relevantClauses.clear();
+        if(relevantOntology != null)
+            relevantOntology.getOWLOntologyManager().removeOntology(relevantOntology);
+        answerVariables = null;
+    }
+
+    public boolean canBeEncodedIntoAtom() {
+        if(isDisposed()) throw new DisposedException();
+
+        // FIXME
+        return true;
 //              return false;
-        }
-
-        public boolean isPredicate(AnswerTuple a, int i) {
-                Atom[] atoms = getClause().getBodyAtoms();
-                Variable v = Variable.create(answerVariables[1][i]);
-                String iri;
-                for(Atom atom : atoms) {
-                        DLPredicate p = atom.getDLPredicate();
-                        if (p instanceof AtomicConcept) {
-                                if(((AtomicConcept) p).getIRI().equals(v.toString())) return true;
-                        }
-                        else if (p instanceof AtomicRole) {
-                                iri = ((AtomicRole) p).getIRI();
-                                if (iri.equals(v.toString())) return true;
-                                if(iri.startsWith("?"))
-                                        iri = a.getGroundTerm(i).toString();
-                                if(iri.equals(Namespace.RDF_TYPE) && atom.getArgument(1).equals(v)) return true;
-                        }
-                }
-                return false;
-        }
-
-        // TODO remove fully extended query
-        public Tuple<String> getExtendedQueryText() {
+    }
+
+    public boolean isPredicate(AnswerTuple a, int i) {
+        if(isDisposed()) throw new DisposedException();
+
+        Atom[] atoms = getClause().getBodyAtoms();
+        Variable v = Variable.create(answerVariables[1][i]);
+        String iri;
+        for(Atom atom : atoms) {
+            DLPredicate p = atom.getDLPredicate();
+            if(p instanceof AtomicConcept) {
+                if(((AtomicConcept) p).getIRI().equals(v.toString())) return true;
+            }
+            else if(p instanceof AtomicRole) {
+                iri = ((AtomicRole) p).getIRI();
+                if(iri.equals(v.toString())) return true;
+                if(iri.startsWith("?"))
+                    iri = a.getGroundTerm(i).toString();
+                if(iri.equals(Namespace.RDF_TYPE) && atom.getArgument(1).equals(v)) return true;
+            }
+        }
+        return false;
+    }
+
+    // TODO remove fully extended query
+    public Tuple<String> getExtendedQueryText() {
+        if(isDisposed()) throw new DisposedException();
+
 //              String[] ret = new String[2];s
-                int index = queryText.toUpperCase().indexOf(" WHERE");
-                String extendedSelect = queryText.substring(0, index);
-                String extendedWhere= queryText.substring(index + 1), fullyExtendedWhere = queryText.substring(index + 1);
-
-                String sub, obj;
-                Map<String, Set<String>> links = new HashMap<String, Set<String>>();
-                Set<String> list;
-                for (Atom atom: getClause().getBodyAtoms())
-                        if (atom.getDLPredicate() instanceof AtomicRole && atom.getArgument(0) instanceof Variable && atom.getArgument(1) instanceof Variable) {
-                                sub = atom.getArgumentVariable(0).getName();
-                                obj = atom.getArgumentVariable(1).getName();
-                                if((list = links.get(sub)) == null)
-                                        links.put(sub, list = new HashSet<String>());
-                                list.add(obj);
-                                if((list = links.get(obj)) == null)
-                                        links.put(obj, list = new HashSet<String>());
-                                list.add(sub);
-                        }
-
-                StringBuilder extra = new StringBuilder(), fullyExtra = new StringBuilder();
+        int index = queryText.toUpperCase().indexOf(" WHERE");
+        String extendedSelect = queryText.substring(0, index);
+        String extendedWhere = queryText.substring(index + 1), fullyExtendedWhere = queryText.substring(index + 1);
+
+        String sub, obj;
+        Map<String, Set<String>> links = new HashMap<String, Set<String>>();
+        Set<String> list;
+        for(Atom atom : getClause().getBodyAtoms())
+            if(atom.getDLPredicate() instanceof AtomicRole && atom.getArgument(0) instanceof Variable && atom.getArgument(1) instanceof Variable) {
+                sub = atom.getArgumentVariable(0).getName();
+                obj = atom.getArgumentVariable(1).getName();
+                if((list = links.get(sub)) == null)
+                    links.put(sub, list = new HashSet<String>());
+                list.add(obj);
+                if((list = links.get(obj)) == null)
+                    links.put(obj, list = new HashSet<String>());
+                list.add(sub);
+            }
+
+        StringBuilder extra = new StringBuilder(), fullyExtra = new StringBuilder();
 //              if (answerVariables[0] != answerVariables[1]) {
-                        for (int i = answerVariables[0].length; i < answerVariables[1].length; ++i) {
+        for(int i = answerVariables[0].length; i < answerVariables[1].length; ++i) {
 //                      for (int i = 0; i < answerVariables[1].length; ++i) {
-                                fullyExtra.append(" . ?")
-                                                  .append(answerVariables[1][i])
-                                                  .append(" " + RDF_TYPE + " <")
-                                                  .append(Namespace.PAGODA_ORIGINAL)
-                                                  .append(">");
-                                if ((list = links.get(answerVariables[1][i])) == null || list.size() < 2) ;
-                                else {
-                                        extra.append(" . ?")
-                                                 .append(answerVariables[1][i])
-                                                 .append(" " + RDF_TYPE + " <")
-                                                 .append(Namespace.PAGODA_ORIGINAL)
-                                                 .append(">");
-                                }
-                        }
-
-                if(extra.length() > 0) {
-                        extra.append(" }");
-                                extendedWhere = extendedWhere.replace(" }", extendedWhere.contains(". }") ? extra.substring(2) : extra.toString());
-                        }
-
-                if(fullyExtra.length() > 0) {
-                        fullyExtra.append(" }");
-                                fullyExtendedWhere = fullyExtendedWhere.replace(" }", fullyExtendedWhere.contains(". }") ? fullyExtra.substring(2) : fullyExtra.toString());
-                        }
+            fullyExtra.append(" . ?")
+                      .append(answerVariables[1][i])
+                      .append(" " + RDF_TYPE + " <")
+                      .append(Namespace.PAGODA_ORIGINAL)
+                      .append(">");
+            if((list = links.get(answerVariables[1][i])) == null || list.size() < 2) ;
+            else {
+                extra.append(" . ?")
+                     .append(answerVariables[1][i])
+                     .append(" " + RDF_TYPE + " <")
+                     .append(Namespace.PAGODA_ORIGINAL)
+                     .append(">");
+            }
+        }
+
+        if(extra.length() > 0) {
+            extra.append(" }");
+            extendedWhere =
+                    extendedWhere.replace(" }", extendedWhere.contains(". }") ? extra.substring(2) : extra.toString());
+        }
+
+        if(fullyExtra.length() > 0) {
+            fullyExtra.append(" }");
+            fullyExtendedWhere =
+                    fullyExtendedWhere.replace(" }", fullyExtendedWhere.contains(". }") ? fullyExtra.substring(2) : fullyExtra
+                            .toString());
+        }
 //              }
 
-                TupleBuilder result = new TupleBuilder();
-                result.append(extendedSelect + " " + fullyExtendedWhere);
-
-                extra.setLength(0);
-                if (answerVariables[0] != answerVariables[1]) {
-                        for (int i = answerVariables[0].length; i < answerVariables[1].length; ++i)
-                                extra.append(" ?").append(answerVariables[1][i]);
-                        extendedSelect = extendedSelect + extra.toString();
-                }
-                result.append(extendedSelect + " " + extendedWhere);
-
-                return result.build();
-        }
-
-        public boolean hasNonAnsDistinguishedVariables() {
-                return answerVariables[1].length > answerVariables[0].length;
-        }
-
-        /**
-         * Two <tt>QueryRecords</tt> are equal iff
-         * they have the same <tt>queryText</tt>,
-         * <tt>soundAnswerTuples</tt>.
-         */
-        @Override
-        public boolean equals(Object o) {
-                if(!o.getClass().equals(getClass())) return false;
-                QueryRecord that = (QueryRecord) o;
-                return this.queryText.equals(that.queryText)
-                                && soundAnswerTuples.equals(that.soundAnswerTuples);
-        }
-
-        @Override
-        public int hashCode() {
-                return Objects.hash(queryText, soundAnswerTuples);
-        }
-
-        public enum Step {
-                LOWER_BOUND,
-                UPPER_BOUND,
-                SIMPLE_UPPER_BOUND,
-                LAZY_UPPER_BOUND,
-                L_SKOLEM_UPPER_BOUND,
-                EL_LOWER_BOUND,
-                FRAGMENT,
-                FRAGMENT_REFINEMENT,
-                SUMMARISATION,
-                DEPENDENCY,
-                FULL_REASONING
-        }
-
-        /**
-         * A Json serializer, which considers the main attributes.
-         */
-        public static class QueryRecordSerializer implements JsonSerializer<QueryRecord> {
-                public JsonElement serialize(QueryRecord src, Type typeOfSrc, JsonSerializationContext context) {
-                        Gson gson = new GsonBuilder().setPrettyPrinting().create();
-                        JsonObject object = new JsonObject();
-                        object.addProperty("queryID", src.queryID);
-                        object.addProperty("queryText", src.queryText);
+        TupleBuilder result = new TupleBuilder();
+        result.append(extendedSelect + " " + fullyExtendedWhere);
+
+        extra.setLength(0);
+        if(answerVariables[0] != answerVariables[1]) {
+            for(int i = answerVariables[0].length; i < answerVariables[1].length; ++i)
+                extra.append(" ?").append(answerVariables[1][i]);
+            extendedSelect = extendedSelect + extra.toString();
+        }
+        result.append(extendedSelect + " " + extendedWhere);
+
+        return result.build();
+    }
+
+    public boolean hasNonAnsDistinguishedVariables() {
+        if(isDisposed()) throw new DisposedException();
+
+        return answerVariables[1].length > answerVariables[0].length;
+    }
+
+    /**
+     * Two <tt>QueryRecords</tt> are equal iff
+     * they have the same <tt>queryText</tt>,
+     * <tt>soundAnswerTuples</tt>.
+     */
+    @Override
+    public boolean equals(Object o) {
+        if(isDisposed()) throw new DisposedException();
+
+        if(!o.getClass().equals(getClass())) return false;
+        QueryRecord that = (QueryRecord) o;
+        return this.queryText.equals(that.queryText)
+                && soundAnswerTuples.equals(that.soundAnswerTuples);
+    }
+
+    @Override
+    public int hashCode() {
+        if(isDisposed()) throw new DisposedException();
+
+        return Objects.hash(queryText, soundAnswerTuples);
+    }
+
+    public enum Step {
+        LOWER_BOUND,
+        UPPER_BOUND,
+        SIMPLE_UPPER_BOUND,
+        LAZY_UPPER_BOUND,
+        L_SKOLEM_UPPER_BOUND,
+        EL_LOWER_BOUND,
+        FRAGMENT,
+        FRAGMENT_REFINEMENT,
+        SUMMARISATION,
+        DEPENDENCY,
+        FULL_REASONING
+    }
+
+    /**
+     * A Json serializer, which considers the main attributes.
+     */
+    public static class QueryRecordSerializer implements JsonSerializer<QueryRecord> {
+        public JsonElement serialize(QueryRecord src, Type typeOfSrc, JsonSerializationContext context) {
+            Gson gson = new GsonBuilder().setPrettyPrinting().create();
+            JsonObject object = new JsonObject();
+            object.addProperty("queryID", src.queryID);
+            object.addProperty("queryText", src.queryText);
 //                      object.addProperty("difficulty", src.difficulty != null ? src.difficulty.toString() : "");
 
-                        object.add("answerVariables", context.serialize(src.getAnswerVariables()));
-                        object.add("answers", context.serialize(src.soundAnswerTuples));
+            object.add("answerVariables", context.serialize(src.getAnswerVariables()));
+            object.add("answers", context.serialize(src.soundAnswerTuples));
 //                      object.add("gapAnswers", context.serialize(src.gapAnswerTuples));
 
-                        return object;
-                }
-        }
-
-        /**
-         * A Json deserializer, compliant to the output of the serializer defined above.
-         */
-        public static class QueryRecordDeserializer implements JsonDeserializer<QueryRecord> {
-                public QueryRecord deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
-                                throws JsonParseException {
-
-                        QueryRecord record = new QueryRecord();
-                        JsonObject object = json.getAsJsonObject();
-                        record.queryID = object.getAsJsonPrimitive("queryID").getAsInt();
-                        record.queryText = object.getAsJsonPrimitive("queryText").getAsString();
+            return object;
+        }
+    }
+
+    /**
+     * A Json deserializer, compliant to the output of the serializer defined above.
+     */
+    public static class QueryRecordDeserializer implements JsonDeserializer<QueryRecord> {
+        public QueryRecord deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
+                throws JsonParseException {
+
+            QueryRecord record = new QueryRecord();
+            JsonObject object = json.getAsJsonObject();
+            record.queryID = object.getAsJsonPrimitive("queryID").getAsInt();
+            record.queryText = object.getAsJsonPrimitive("queryText").getAsString();
 //                      record.difficulty = Step.valueOf(object.getAsJsonPrimitive("difficulty").getAsString());
 
-                        JsonArray answerVariablesJson = object.getAsJsonArray("answerVariables");
-                        record.answerVariables = new String[2][];
-                        record.answerVariables[0] = new String[answerVariablesJson.size()];
-                        for(int i = 0; i < answerVariablesJson.size(); i++)
-                                record.answerVariables[0][i] = answerVariablesJson.get(i).getAsString();
+            JsonArray answerVariablesJson = object.getAsJsonArray("answerVariables");
+            record.answerVariables = new String[2][];
+            record.answerVariables[0] = new String[answerVariablesJson.size()];
+            for(int i = 0; i < answerVariablesJson.size(); i++)
+                record.answerVariables[0][i] = answerVariablesJson.get(i).getAsString();
 
-                        record.soundAnswerTuples = new HashSet<>();
+            record.soundAnswerTuples = new HashSet<>();
 //                      record.gapAnswerTuples = new HashSet<>();
-                        Type type = new TypeToken<AnswerTuple>() { }.getType();
-                        for (JsonElement answer : object.getAsJsonArray("answers")) {
-                                record.soundAnswerTuples.add(context.deserialize(answer, type));
-                        }
+            Type type = new TypeToken<AnswerTuple>() {
+            }.getType();
+            for(JsonElement answer : object.getAsJsonArray("answers")) {
+                record.soundAnswerTuples.add(context.deserialize(answer, type));
+            }
 //                      for (JsonElement answer : object.getAsJsonArray("gapAnswers")) {
 //                              record.soundAnswerTuples.add(context.deserialize(answer, type));
 //                      }
 
-                        return record;
-                }
-        }
-
-        /**
-         * Provides an instance (singleton) of Gson, having a specific configuration.
-         * */
-        public static class GsonCreator {
-
-                private static Gson gson;
-
-                private GsonCreator() {}
-
-                public static Gson getInstance() {
-                        if(gson == null) {
-                                gson = new GsonBuilder()
-                                                .registerTypeAdapter(AnswerTuple.class, new AnswerTuple.AnswerTupleSerializer())
-                                                .registerTypeAdapter(QueryRecord.class, new QueryRecord.QueryRecordSerializer())
-                                                .registerTypeAdapter(QueryRecord.class, new QueryRecord.QueryRecordDeserializer())
-                                                .registerTypeAdapter(AnswerTuple.class, new AnswerTuple.AnswerTupleDeserializer())
-                                                .disableHtmlEscaping()
-                                                .setPrettyPrinting()
-                                                .create();
-                        }
-                        return gson;
-                }
+            return record;
+        }
+    }
+
+    /**
+     * Provides an instance (singleton) of Gson, having a specific configuration.
+     */
+    public static class GsonCreator {
+
+        private static Gson gson;
+
+        private GsonCreator() {
+        }
+
+        public static Gson getInstance() {
+            if(gson == null) {
+                gson = new GsonBuilder()
+                        .registerTypeAdapter(AnswerTuple.class, new AnswerTuple.AnswerTupleSerializer())
+                        .registerTypeAdapter(QueryRecord.class, new QueryRecord.QueryRecordSerializer())
+                        .registerTypeAdapter(QueryRecord.class, new QueryRecord.QueryRecordDeserializer())
+                        .registerTypeAdapter(AnswerTuple.class, new AnswerTuple.AnswerTupleDeserializer())
+                        .disableHtmlEscaping()
+                        .setPrettyPrinting()
+                        .create();
+            }
+            return gson;
+        }
 
 //              public static void dispose() {
 //                      gson = null;
 //              }
 
-        }
+    }
 }