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diff --git a/Metrics/Metrics-Calculation/SocialNetwork_plugin/src-gen/queries/NonSymmetricOpposite.java b/Metrics/Metrics-Calculation/SocialNetwork_plugin/src-gen/queries/NonSymmetricOpposite.java
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+++ b/Metrics/Metrics-Calculation/SocialNetwork_plugin/src-gen/queries/NonSymmetricOpposite.java
@@ -0,0 +1,718 @@
+/**
+ * Generated from platform:/resource/SocialNetwork_plugin/queries/queries/Ecore.vql
+ */
+package queries;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
+import java.util.function.Consumer;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+import org.apache.log4j.Logger;
+import org.eclipse.emf.ecore.EClass;
+import org.eclipse.emf.ecore.EReference;
+import org.eclipse.viatra.query.runtime.api.IPatternMatch;
+import org.eclipse.viatra.query.runtime.api.IQuerySpecification;
+import org.eclipse.viatra.query.runtime.api.ViatraQueryEngine;
+import org.eclipse.viatra.query.runtime.api.impl.BaseGeneratedEMFPQuery;
+import org.eclipse.viatra.query.runtime.api.impl.BaseGeneratedEMFQuerySpecification;
+import org.eclipse.viatra.query.runtime.api.impl.BaseMatcher;
+import org.eclipse.viatra.query.runtime.api.impl.BasePatternMatch;
+import org.eclipse.viatra.query.runtime.emf.types.EClassTransitiveInstancesKey;
+import org.eclipse.viatra.query.runtime.matchers.backend.QueryEvaluationHint;
+import org.eclipse.viatra.query.runtime.matchers.psystem.PBody;
+import org.eclipse.viatra.query.runtime.matchers.psystem.PVariable;
+import org.eclipse.viatra.query.runtime.matchers.psystem.annotations.PAnnotation;
+import org.eclipse.viatra.query.runtime.matchers.psystem.annotations.ParameterReference;
+import org.eclipse.viatra.query.runtime.matchers.psystem.basicdeferred.ExportedParameter;
+import org.eclipse.viatra.query.runtime.matchers.psystem.basicdeferred.NegativePatternCall;
+import org.eclipse.viatra.query.runtime.matchers.psystem.basicenumerables.PositivePatternCall;
+import org.eclipse.viatra.query.runtime.matchers.psystem.basicenumerables.TypeConstraint;
+import org.eclipse.viatra.query.runtime.matchers.psystem.queries.PParameter;
+import org.eclipse.viatra.query.runtime.matchers.psystem.queries.PParameterDirection;
+import org.eclipse.viatra.query.runtime.matchers.psystem.queries.PVisibility;
+import org.eclipse.viatra.query.runtime.matchers.tuple.Tuple;
+import org.eclipse.viatra.query.runtime.matchers.tuple.Tuples;
+import org.eclipse.viatra.query.runtime.util.ViatraQueryLoggingUtil;
+import queries.Opposite;
+
+/**
+ * A pattern-specific query specification that can instantiate Matcher in a type-safe way.
+ * 
+ * <p>Original source:
+ *         <code><pre>
+ *         {@literal @}Constraint(key={a}, severity="error", message="error")
+ *         pattern nonSymmetricOpposite(a:EReference, b:EReference) {
+ *              find opposite(a,b);
+ *              neg find opposite(b,a);
+ *         }
+ * </pre></code>
+ * 
+ * @see Matcher
+ * @see Match
+ * 
+ */
+@SuppressWarnings("all")
+public final class NonSymmetricOpposite extends BaseGeneratedEMFQuerySpecification<NonSymmetricOpposite.Matcher> {
+  /**
+   * Pattern-specific match representation of the queries.nonSymmetricOpposite pattern,
+   * to be used in conjunction with {@link Matcher}.
+   * 
+   * <p>Class fields correspond to parameters of the pattern. Fields with value null are considered unassigned.
+   * Each instance is a (possibly partial) substitution of pattern parameters,
+   * usable to represent a match of the pattern in the result of a query,
+   * or to specify the bound (fixed) input parameters when issuing a query.
+   * 
+   * @see Matcher
+   * 
+   */
+  public static abstract class Match extends BasePatternMatch {
+    private EReference fA;
+    
+    private EReference fB;
+    
+    private static List<String> parameterNames = makeImmutableList("a", "b");
+    
+    private Match(final EReference pA, final EReference pB) {
+      this.fA = pA;
+      this.fB = pB;
+    }
+    
+    @Override
+    public Object get(final String parameterName) {
+      switch(parameterName) {
+          case "a": return this.fA;
+          case "b": return this.fB;
+          default: return null;
+      }
+    }
+    
+    @Override
+    public Object get(final int index) {
+      switch(index) {
+          case 0: return this.fA;
+          case 1: return this.fB;
+          default: return null;
+      }
+    }
+    
+    public EReference getA() {
+      return this.fA;
+    }
+    
+    public EReference getB() {
+      return this.fB;
+    }
+    
+    @Override
+    public boolean set(final String parameterName, final Object newValue) {
+      if (!isMutable()) throw new java.lang.UnsupportedOperationException();
+      if ("a".equals(parameterName) ) {
+          this.fA = (EReference) newValue;
+          return true;
+      }
+      if ("b".equals(parameterName) ) {
+          this.fB = (EReference) newValue;
+          return true;
+      }
+      return false;
+    }
+    
+    public void setA(final EReference pA) {
+      if (!isMutable()) throw new java.lang.UnsupportedOperationException();
+      this.fA = pA;
+    }
+    
+    public void setB(final EReference pB) {
+      if (!isMutable()) throw new java.lang.UnsupportedOperationException();
+      this.fB = pB;
+    }
+    
+    @Override
+    public String patternName() {
+      return "queries.nonSymmetricOpposite";
+    }
+    
+    @Override
+    public List<String> parameterNames() {
+      return NonSymmetricOpposite.Match.parameterNames;
+    }
+    
+    @Override
+    public Object[] toArray() {
+      return new Object[]{fA, fB};
+    }
+    
+    @Override
+    public NonSymmetricOpposite.Match toImmutable() {
+      return isMutable() ? newMatch(fA, fB) : this;
+    }
+    
+    @Override
+    public String prettyPrint() {
+      StringBuilder result = new StringBuilder();
+      result.append("\"a\"=" + prettyPrintValue(fA) + ", ");
+      result.append("\"b\"=" + prettyPrintValue(fB));
+      return result.toString();
+    }
+    
+    @Override
+    public int hashCode() {
+      return Objects.hash(fA, fB);
+    }
+    
+    @Override
+    public boolean equals(final Object obj) {
+      if (this == obj)
+          return true;
+      if (obj == null) {
+          return false;
+      }
+      if ((obj instanceof NonSymmetricOpposite.Match)) {
+          NonSymmetricOpposite.Match other = (NonSymmetricOpposite.Match) obj;
+          return Objects.equals(fA, other.fA) && Objects.equals(fB, other.fB);
+      } else {
+          // this should be infrequent
+          if (!(obj instanceof IPatternMatch)) {
+              return false;
+          }
+          IPatternMatch otherSig  = (IPatternMatch) obj;
+          return Objects.equals(specification(), otherSig.specification()) && Arrays.deepEquals(toArray(), otherSig.toArray());
+      }
+    }
+    
+    @Override
+    public NonSymmetricOpposite specification() {
+      return NonSymmetricOpposite.instance();
+    }
+    
+    /**
+     * Returns an empty, mutable match.
+     * Fields of the mutable match can be filled to create a partial match, usable as matcher input.
+     * 
+     * @return the empty match.
+     * 
+     */
+    public static NonSymmetricOpposite.Match newEmptyMatch() {
+      return new Mutable(null, null);
+    }
+    
+    /**
+     * Returns a mutable (partial) match.
+     * Fields of the mutable match can be filled to create a partial match, usable as matcher input.
+     * 
+     * @param pA the fixed value of pattern parameter a, or null if not bound.
+     * @param pB the fixed value of pattern parameter b, or null if not bound.
+     * @return the new, mutable (partial) match object.
+     * 
+     */
+    public static NonSymmetricOpposite.Match newMutableMatch(final EReference pA, final EReference pB) {
+      return new Mutable(pA, pB);
+    }
+    
+    /**
+     * Returns a new (partial) match.
+     * This can be used e.g. to call the matcher with a partial match.
+     * <p>The returned match will be immutable. Use {@link #newEmptyMatch()} to obtain a mutable match object.
+     * @param pA the fixed value of pattern parameter a, or null if not bound.
+     * @param pB the fixed value of pattern parameter b, or null if not bound.
+     * @return the (partial) match object.
+     * 
+     */
+    public static NonSymmetricOpposite.Match newMatch(final EReference pA, final EReference pB) {
+      return new Immutable(pA, pB);
+    }
+    
+    private static final class Mutable extends NonSymmetricOpposite.Match {
+      Mutable(final EReference pA, final EReference pB) {
+        super(pA, pB);
+      }
+      
+      @Override
+      public boolean isMutable() {
+        return true;
+      }
+    }
+    
+    private static final class Immutable extends NonSymmetricOpposite.Match {
+      Immutable(final EReference pA, final EReference pB) {
+        super(pA, pB);
+      }
+      
+      @Override
+      public boolean isMutable() {
+        return false;
+      }
+    }
+  }
+  
+  /**
+   * Generated pattern matcher API of the queries.nonSymmetricOpposite pattern,
+   * providing pattern-specific query methods.
+   * 
+   * <p>Use the pattern matcher on a given model via {@link #on(ViatraQueryEngine)},
+   * e.g. in conjunction with {@link ViatraQueryEngine#on(QueryScope)}.
+   * 
+   * <p>Matches of the pattern will be represented as {@link Match}.
+   * 
+   * <p>Original source:
+   * <code><pre>
+   * {@literal @}Constraint(key={a}, severity="error", message="error")
+   * pattern nonSymmetricOpposite(a:EReference, b:EReference) {
+   *    find opposite(a,b);
+   *    neg find opposite(b,a);
+   * }
+   * </pre></code>
+   * 
+   * @see Match
+   * @see NonSymmetricOpposite
+   * 
+   */
+  public static class Matcher extends BaseMatcher<NonSymmetricOpposite.Match> {
+    /**
+     * Initializes the pattern matcher within an existing VIATRA Query engine.
+     * If the pattern matcher is already constructed in the engine, only a light-weight reference is returned.
+     * 
+     * @param engine the existing VIATRA Query engine in which this matcher will be created.
+     * @throws ViatraQueryRuntimeException if an error occurs during pattern matcher creation
+     * 
+     */
+    public static NonSymmetricOpposite.Matcher on(final ViatraQueryEngine engine) {
+      // check if matcher already exists
+      Matcher matcher = engine.getExistingMatcher(querySpecification());
+      if (matcher == null) {
+          matcher = (Matcher)engine.getMatcher(querySpecification());
+      }
+      return matcher;
+    }
+    
+    /**
+     * @throws ViatraQueryRuntimeException if an error occurs during pattern matcher creation
+     * @return an initialized matcher
+     * @noreference This method is for internal matcher initialization by the framework, do not call it manually.
+     * 
+     */
+    public static NonSymmetricOpposite.Matcher create() {
+      return new Matcher();
+    }
+    
+    private static final int POSITION_A = 0;
+    
+    private static final int POSITION_B = 1;
+    
+    private static final Logger LOGGER = ViatraQueryLoggingUtil.getLogger(NonSymmetricOpposite.Matcher.class);
+    
+    /**
+     * Initializes the pattern matcher within an existing VIATRA Query engine.
+     * If the pattern matcher is already constructed in the engine, only a light-weight reference is returned.
+     * 
+     * @param engine the existing VIATRA Query engine in which this matcher will be created.
+     * @throws ViatraQueryRuntimeException if an error occurs during pattern matcher creation
+     * 
+     */
+    private Matcher() {
+      super(querySpecification());
+    }
+    
+    /**
+     * Returns the set of all matches of the pattern that conform to the given fixed values of some parameters.
+     * @param pA the fixed value of pattern parameter a, or null if not bound.
+     * @param pB the fixed value of pattern parameter b, or null if not bound.
+     * @return matches represented as a Match object.
+     * 
+     */
+    public Collection<NonSymmetricOpposite.Match> getAllMatches(final EReference pA, final EReference pB) {
+      return rawStreamAllMatches(new Object[]{pA, pB}).collect(Collectors.toSet());
+    }
+    
+    /**
+     * Returns a stream of all matches of the pattern that conform to the given fixed values of some parameters.
+     * </p>
+     * <strong>NOTE</strong>: It is important not to modify the source model while the stream is being processed.
+     * If the match set of the pattern changes during processing, the contents of the stream is <strong>undefined</strong>.
+     * In such cases, either rely on {@link #getAllMatches()} or collect the results of the stream in end-user code.
+     * @param pA the fixed value of pattern parameter a, or null if not bound.
+     * @param pB the fixed value of pattern parameter b, or null if not bound.
+     * @return a stream of matches represented as a Match object.
+     * 
+     */
+    public Stream<NonSymmetricOpposite.Match> streamAllMatches(final EReference pA, final EReference pB) {
+      return rawStreamAllMatches(new Object[]{pA, pB});
+    }
+    
+    /**
+     * Returns an arbitrarily chosen match of the pattern that conforms to the given fixed values of some parameters.
+     * Neither determinism nor randomness of selection is guaranteed.
+     * @param pA the fixed value of pattern parameter a, or null if not bound.
+     * @param pB the fixed value of pattern parameter b, or null if not bound.
+     * @return a match represented as a Match object, or null if no match is found.
+     * 
+     */
+    public Optional<NonSymmetricOpposite.Match> getOneArbitraryMatch(final EReference pA, final EReference pB) {
+      return rawGetOneArbitraryMatch(new Object[]{pA, pB});
+    }
+    
+    /**
+     * Indicates whether the given combination of specified pattern parameters constitute a valid pattern match,
+     * under any possible substitution of the unspecified parameters (if any).
+     * @param pA the fixed value of pattern parameter a, or null if not bound.
+     * @param pB the fixed value of pattern parameter b, or null if not bound.
+     * @return true if the input is a valid (partial) match of the pattern.
+     * 
+     */
+    public boolean hasMatch(final EReference pA, final EReference pB) {
+      return rawHasMatch(new Object[]{pA, pB});
+    }
+    
+    /**
+     * Returns the number of all matches of the pattern that conform to the given fixed values of some parameters.
+     * @param pA the fixed value of pattern parameter a, or null if not bound.
+     * @param pB the fixed value of pattern parameter b, or null if not bound.
+     * @return the number of pattern matches found.
+     * 
+     */
+    public int countMatches(final EReference pA, final EReference pB) {
+      return rawCountMatches(new Object[]{pA, pB});
+    }
+    
+    /**
+     * Executes the given processor on an arbitrarily chosen match of the pattern that conforms to the given fixed values of some parameters.
+     * Neither determinism nor randomness of selection is guaranteed.
+     * @param pA the fixed value of pattern parameter a, or null if not bound.
+     * @param pB the fixed value of pattern parameter b, or null if not bound.
+     * @param processor the action that will process the selected match.
+     * @return true if the pattern has at least one match with the given parameter values, false if the processor was not invoked
+     * 
+     */
+    public boolean forOneArbitraryMatch(final EReference pA, final EReference pB, final Consumer<? super NonSymmetricOpposite.Match> processor) {
+      return rawForOneArbitraryMatch(new Object[]{pA, pB}, processor);
+    }
+    
+    /**
+     * Returns a new (partial) match.
+     * This can be used e.g. to call the matcher with a partial match.
+     * <p>The returned match will be immutable. Use {@link #newEmptyMatch()} to obtain a mutable match object.
+     * @param pA the fixed value of pattern parameter a, or null if not bound.
+     * @param pB the fixed value of pattern parameter b, or null if not bound.
+     * @return the (partial) match object.
+     * 
+     */
+    public NonSymmetricOpposite.Match newMatch(final EReference pA, final EReference pB) {
+      return NonSymmetricOpposite.Match.newMatch(pA, pB);
+    }
+    
+    /**
+     * Retrieve the set of values that occur in matches for a.
+     * @return the Set of all values or empty set if there are no matches
+     * 
+     */
+    protected Stream<EReference> rawStreamAllValuesOfa(final Object[] parameters) {
+      return rawStreamAllValues(POSITION_A, parameters).map(EReference.class::cast);
+    }
+    
+    /**
+     * Retrieve the set of values that occur in matches for a.
+     * @return the Set of all values or empty set if there are no matches
+     * 
+     */
+    public Set<EReference> getAllValuesOfa() {
+      return rawStreamAllValuesOfa(emptyArray()).collect(Collectors.toSet());
+    }
+    
+    /**
+     * Retrieve the set of values that occur in matches for a.
+     * @return the Set of all values or empty set if there are no matches
+     * 
+     */
+    public Stream<EReference> streamAllValuesOfa() {
+      return rawStreamAllValuesOfa(emptyArray());
+    }
+    
+    /**
+     * Retrieve the set of values that occur in matches for a.
+     * </p>
+     * <strong>NOTE</strong>: It is important not to modify the source model while the stream is being processed.
+     * If the match set of the pattern changes during processing, the contents of the stream is <strong>undefined</strong>.
+     * In such cases, either rely on {@link #getAllMatches()} or collect the results of the stream in end-user code.
+     *      
+     * @return the Stream of all values or empty set if there are no matches
+     * 
+     */
+    public Stream<EReference> streamAllValuesOfa(final NonSymmetricOpposite.Match partialMatch) {
+      return rawStreamAllValuesOfa(partialMatch.toArray());
+    }
+    
+    /**
+     * Retrieve the set of values that occur in matches for a.
+     * </p>
+     * <strong>NOTE</strong>: It is important not to modify the source model while the stream is being processed.
+     * If the match set of the pattern changes during processing, the contents of the stream is <strong>undefined</strong>.
+     * In such cases, either rely on {@link #getAllMatches()} or collect the results of the stream in end-user code.
+     *      
+     * @return the Stream of all values or empty set if there are no matches
+     * 
+     */
+    public Stream<EReference> streamAllValuesOfa(final EReference pB) {
+      return rawStreamAllValuesOfa(new Object[]{null, pB});
+    }
+    
+    /**
+     * Retrieve the set of values that occur in matches for a.
+     * @return the Set of all values or empty set if there are no matches
+     * 
+     */
+    public Set<EReference> getAllValuesOfa(final NonSymmetricOpposite.Match partialMatch) {
+      return rawStreamAllValuesOfa(partialMatch.toArray()).collect(Collectors.toSet());
+    }
+    
+    /**
+     * Retrieve the set of values that occur in matches for a.
+     * @return the Set of all values or empty set if there are no matches
+     * 
+     */
+    public Set<EReference> getAllValuesOfa(final EReference pB) {
+      return rawStreamAllValuesOfa(new Object[]{null, pB}).collect(Collectors.toSet());
+    }
+    
+    /**
+     * Retrieve the set of values that occur in matches for b.
+     * @return the Set of all values or empty set if there are no matches
+     * 
+     */
+    protected Stream<EReference> rawStreamAllValuesOfb(final Object[] parameters) {
+      return rawStreamAllValues(POSITION_B, parameters).map(EReference.class::cast);
+    }
+    
+    /**
+     * Retrieve the set of values that occur in matches for b.
+     * @return the Set of all values or empty set if there are no matches
+     * 
+     */
+    public Set<EReference> getAllValuesOfb() {
+      return rawStreamAllValuesOfb(emptyArray()).collect(Collectors.toSet());
+    }
+    
+    /**
+     * Retrieve the set of values that occur in matches for b.
+     * @return the Set of all values or empty set if there are no matches
+     * 
+     */
+    public Stream<EReference> streamAllValuesOfb() {
+      return rawStreamAllValuesOfb(emptyArray());
+    }
+    
+    /**
+     * Retrieve the set of values that occur in matches for b.
+     * </p>
+     * <strong>NOTE</strong>: It is important not to modify the source model while the stream is being processed.
+     * If the match set of the pattern changes during processing, the contents of the stream is <strong>undefined</strong>.
+     * In such cases, either rely on {@link #getAllMatches()} or collect the results of the stream in end-user code.
+     *      
+     * @return the Stream of all values or empty set if there are no matches
+     * 
+     */
+    public Stream<EReference> streamAllValuesOfb(final NonSymmetricOpposite.Match partialMatch) {
+      return rawStreamAllValuesOfb(partialMatch.toArray());
+    }
+    
+    /**
+     * Retrieve the set of values that occur in matches for b.
+     * </p>
+     * <strong>NOTE</strong>: It is important not to modify the source model while the stream is being processed.
+     * If the match set of the pattern changes during processing, the contents of the stream is <strong>undefined</strong>.
+     * In such cases, either rely on {@link #getAllMatches()} or collect the results of the stream in end-user code.
+     *      
+     * @return the Stream of all values or empty set if there are no matches
+     * 
+     */
+    public Stream<EReference> streamAllValuesOfb(final EReference pA) {
+      return rawStreamAllValuesOfb(new Object[]{pA, null});
+    }
+    
+    /**
+     * Retrieve the set of values that occur in matches for b.
+     * @return the Set of all values or empty set if there are no matches
+     * 
+     */
+    public Set<EReference> getAllValuesOfb(final NonSymmetricOpposite.Match partialMatch) {
+      return rawStreamAllValuesOfb(partialMatch.toArray()).collect(Collectors.toSet());
+    }
+    
+    /**
+     * Retrieve the set of values that occur in matches for b.
+     * @return the Set of all values or empty set if there are no matches
+     * 
+     */
+    public Set<EReference> getAllValuesOfb(final EReference pA) {
+      return rawStreamAllValuesOfb(new Object[]{pA, null}).collect(Collectors.toSet());
+    }
+    
+    @Override
+    protected NonSymmetricOpposite.Match tupleToMatch(final Tuple t) {
+      try {
+          return NonSymmetricOpposite.Match.newMatch((EReference) t.get(POSITION_A), (EReference) t.get(POSITION_B));
+      } catch(ClassCastException e) {
+          LOGGER.error("Element(s) in tuple not properly typed!",e);
+          return null;
+      }
+    }
+    
+    @Override
+    protected NonSymmetricOpposite.Match arrayToMatch(final Object[] match) {
+      try {
+          return NonSymmetricOpposite.Match.newMatch((EReference) match[POSITION_A], (EReference) match[POSITION_B]);
+      } catch(ClassCastException e) {
+          LOGGER.error("Element(s) in array not properly typed!",e);
+          return null;
+      }
+    }
+    
+    @Override
+    protected NonSymmetricOpposite.Match arrayToMatchMutable(final Object[] match) {
+      try {
+          return NonSymmetricOpposite.Match.newMutableMatch((EReference) match[POSITION_A], (EReference) match[POSITION_B]);
+      } catch(ClassCastException e) {
+          LOGGER.error("Element(s) in array not properly typed!",e);
+          return null;
+      }
+    }
+    
+    /**
+     * @return the singleton instance of the query specification of this pattern
+     * @throws ViatraQueryRuntimeException if the pattern definition could not be loaded
+     * 
+     */
+    public static IQuerySpecification<NonSymmetricOpposite.Matcher> querySpecification() {
+      return NonSymmetricOpposite.instance();
+    }
+  }
+  
+  private NonSymmetricOpposite() {
+    super(GeneratedPQuery.INSTANCE);
+  }
+  
+  /**
+   * @return the singleton instance of the query specification
+   * @throws ViatraQueryRuntimeException if the pattern definition could not be loaded
+   * 
+   */
+  public static NonSymmetricOpposite instance() {
+    try{
+        return LazyHolder.INSTANCE;
+    } catch (ExceptionInInitializerError err) {
+        throw processInitializerError(err);
+    }
+  }
+  
+  @Override
+  protected NonSymmetricOpposite.Matcher instantiate(final ViatraQueryEngine engine) {
+    return NonSymmetricOpposite.Matcher.on(engine);
+  }
+  
+  @Override
+  public NonSymmetricOpposite.Matcher instantiate() {
+    return NonSymmetricOpposite.Matcher.create();
+  }
+  
+  @Override
+  public NonSymmetricOpposite.Match newEmptyMatch() {
+    return NonSymmetricOpposite.Match.newEmptyMatch();
+  }
+  
+  @Override
+  public NonSymmetricOpposite.Match newMatch(final Object... parameters) {
+    return NonSymmetricOpposite.Match.newMatch((org.eclipse.emf.ecore.EReference) parameters[0], (org.eclipse.emf.ecore.EReference) parameters[1]);
+  }
+  
+  /**
+   * Inner class allowing the singleton instance of {@link NonSymmetricOpposite} to be created 
+   *     <b>not</b> at the class load time of the outer class, 
+   *     but rather at the first call to {@link NonSymmetricOpposite#instance()}.
+   * 
+   * <p> This workaround is required e.g. to support recursion.
+   * 
+   */
+  private static class LazyHolder {
+    private static final NonSymmetricOpposite INSTANCE = new NonSymmetricOpposite();
+    
+    /**
+     * Statically initializes the query specification <b>after</b> the field {@link #INSTANCE} is assigned.
+     * This initialization order is required to support indirect recursion.
+     * 
+     * <p> The static initializer is defined using a helper field to work around limitations of the code generator.
+     * 
+     */
+    private static final Object STATIC_INITIALIZER = ensureInitialized();
+    
+    public static Object ensureInitialized() {
+      INSTANCE.ensureInitializedInternal();
+      return null;
+    }
+  }
+  
+  private static class GeneratedPQuery extends BaseGeneratedEMFPQuery {
+    private static final NonSymmetricOpposite.GeneratedPQuery INSTANCE = new GeneratedPQuery();
+    
+    private final PParameter parameter_a = new PParameter("a", "org.eclipse.emf.ecore.EReference", new EClassTransitiveInstancesKey((EClass)getClassifierLiteralSafe("http://www.eclipse.org/emf/2002/Ecore", "EReference")), PParameterDirection.INOUT);
+    
+    private final PParameter parameter_b = new PParameter("b", "org.eclipse.emf.ecore.EReference", new EClassTransitiveInstancesKey((EClass)getClassifierLiteralSafe("http://www.eclipse.org/emf/2002/Ecore", "EReference")), PParameterDirection.INOUT);
+    
+    private final List<PParameter> parameters = Arrays.asList(parameter_a, parameter_b);
+    
+    private GeneratedPQuery() {
+      super(PVisibility.PUBLIC);
+    }
+    
+    @Override
+    public String getFullyQualifiedName() {
+      return "queries.nonSymmetricOpposite";
+    }
+    
+    @Override
+    public List<String> getParameterNames() {
+      return Arrays.asList("a","b");
+    }
+    
+    @Override
+    public List<PParameter> getParameters() {
+      return parameters;
+    }
+    
+    @Override
+    public Set<PBody> doGetContainedBodies() {
+      setEvaluationHints(new QueryEvaluationHint(null, QueryEvaluationHint.BackendRequirement.UNSPECIFIED));
+      Set<PBody> bodies = new LinkedHashSet<>();
+      {
+          PBody body = new PBody(this);
+          PVariable var_a = body.getOrCreateVariableByName("a");
+          PVariable var_b = body.getOrCreateVariableByName("b");
+          new TypeConstraint(body, Tuples.flatTupleOf(var_a), new EClassTransitiveInstancesKey((EClass)getClassifierLiteral("http://www.eclipse.org/emf/2002/Ecore", "EReference")));
+          new TypeConstraint(body, Tuples.flatTupleOf(var_b), new EClassTransitiveInstancesKey((EClass)getClassifierLiteral("http://www.eclipse.org/emf/2002/Ecore", "EReference")));
+          body.setSymbolicParameters(Arrays.<ExportedParameter>asList(
+             new ExportedParameter(body, var_a, parameter_a),
+             new ExportedParameter(body, var_b, parameter_b)
+          ));
+          //    find opposite(a,b)
+          new PositivePatternCall(body, Tuples.flatTupleOf(var_a, var_b), Opposite.instance().getInternalQueryRepresentation());
+          //    neg find opposite(b,a)
+          new NegativePatternCall(body, Tuples.flatTupleOf(var_b, var_a), Opposite.instance().getInternalQueryRepresentation());
+          bodies.add(body);
+      }
+      {
+          PAnnotation annotation = new PAnnotation("Constraint");
+          annotation.addAttribute("key", Arrays.asList(new Object[] {
+                              new ParameterReference("a")
+                              }));
+          annotation.addAttribute("severity", "error");
+          annotation.addAttribute("message", "error");
+          addAnnotation(annotation);
+      }
+      return bodies;
+    }
+  }
+}