diff --git a/include/dlplan/core.h b/include/dlplan/core.h
index 54ac317d..1018ca2e 100644
--- a/include/dlplan/core.h
+++ b/include/dlplan/core.h
@@ -709,80 +709,89 @@ class State {
 };
 
 
-/// @brief Represents the abstract base class of an element with functionality
-///        for computing string representations and its complexity.
+/// @brief Represents the abstract base class of an object
+///        with functionality for computing string representations.
 template<typename Derived>
-class BaseElement {
+class Base {
 protected:
-    std::shared_ptr<VocabularyInfo> m_vocabulary_info;
-    ElementIndex m_index;
-    /**
-     * if true then element is evaluated per instance rather than per state.
-     */
-    bool m_is_static;
+    int m_index;
 
-    BaseElement(std::shared_ptr<VocabularyInfo> vocabulary_info, ElementIndex index, bool is_static)
-        : m_vocabulary_info(vocabulary_info), m_index(index), m_is_static(is_static) { }
+    Base(int index) : m_index(index) { }
 
 public:
-    ~BaseElement() { }
+    ~Base() { }
 
-    bool operator==(const Derived& other) const {
-        return static_cast<const Derived*>(this)->operator==(other);
+    bool operator==(const Base& other) const {
+        return static_cast<const Derived*>(this)->are_equal_impl(static_cast<const Derived&>(other));
     }
 
-    bool operator<(const Derived& other) const {
+    bool operator<(const Base& other) const {
         return m_index < other.m_index;
     }
 
-    /// @brief Computes a hash value for this element.
-    /// @return 
-    size_t hash() const { 
+    /// @brief Computes a hash value for this object.
+    size_t hash() const {
         return static_cast<const Derived*>(this)->hash_impl();
     }
 
-    /// @brief Compute the canonical string representation of this element.
-    /// @return The canonical string representation of this element.
+    /// @brief Compute a canonical string representation of this object.
     std::string compute_repr() const {
-        std::stringstream ss; 
+        std::stringstream ss;
         compute_repr(ss);
         return ss.str();
     }
 
-    /// @brief Helper function to compute the canonical string representation of this element.
+    /// @brief Overload of the output stream insertion operator (operator<<).
+    friend std::ostream& operator<<(std::ostream& os, const Base& element) {
+        os << element.str();
+        return os;
+    }
+
+    /// @brief Compute a canonical string representation of this object.
     void compute_repr(std::stringstream& out) const {
         static_cast<const Derived*>(this)->compute_repr_impl(out);
     }
 
+    /// @brief Compute a string representation of this object.
+    std::string str() const {
+        return static_cast<const Derived*>(this)->str_impl();
+    }
+
+    /* Getters. */
+    int get_index() const { return m_index; }
+};
+
+
+template<typename Derived>
+class BaseElement : public Base<Derived> {
+protected:
+    std::shared_ptr<VocabularyInfo> m_vocabulary_info;
+    bool m_is_static;
+
+public:
+    BaseElement(int index, std::shared_ptr<VocabularyInfo> vocabulary_info, bool is_static)
+        : Base<Derived>(index), m_vocabulary_info(vocabulary_info), m_is_static(is_static) { }
+
+    ~BaseElement() { }
+
     /// @brief Returns the complexity of the element
     ///        measured in the size of the abstract syntax tree.
-    /// @return An integer that represents the number of element constructors in the represenation.
     int compute_complexity() const {
         return static_cast<const Derived*>(this)->compute_complexity_impl();
     }
 
     /// @brief Computes a time score for evaluating this element relative to other elements.
     ///        The scoring assumes evaluation that uses caching.
-    /// @return An integer that represents the score.
     int compute_evaluate_time_score() const {
         return static_cast<const Derived*>(this)->compute_evaluate_time_score_impl();
     }
 
-    /// @brief Overload of the output stream insertion operator (operator<<) for the BaseElement class.
-    ///        Outputs a string representation of a BaseElement object to the specified output stream.
-    /// @param os The output stream to write the string representation to.
-    /// @param denotation The BaseElement to be represented as a string.
-    /// @return A reference to the output stream after writing the string representation.
-    friend std::ostream& operator<<(std::ostream& os, const BaseElement& element) { 
-        os << element.compute_repr();
-        return os;
+    // For elements we simply return repr as a string representation.
+    std::string str_impl() const {
+        return Base<Derived>::compute_repr();
     }
 
-    /// @brief Compute a string representation of this element.
-    /// @return A string representation of this element.
-    std::string str() const { return compute_repr(); }
-
-    ElementIndex get_index() const { return m_index; }
+    /* Getters. */
     std::shared_ptr<VocabularyInfo> get_vocabulary_info() const { return m_vocabulary_info; }
     bool is_static() const { return m_is_static; }
 };
@@ -804,8 +813,7 @@ class Concept : public BaseElement<Concept> {
     Concept& operator=(Concept&& other);
     ~Concept();
 
-    virtual bool operator==(const Concept& other) const = 0;
-
+    virtual bool are_equal_impl(const Concept& other) const = 0;
     virtual size_t hash_impl() const = 0;
     virtual void compute_repr_impl(std::stringstream& out) const = 0;
     virtual int compute_complexity_impl() const = 0;
@@ -833,8 +841,7 @@ class Role : public BaseElement<Role> {
     Role& operator=(Role&& other);
     ~Role();
 
-    virtual bool operator==(const Role& other) const = 0;
-
+    virtual bool are_equal_impl(const Role& other) const = 0;
     virtual size_t hash_impl() const = 0;
     virtual void compute_repr_impl(std::stringstream& out) const = 0;
     virtual int compute_complexity_impl() const = 0;
@@ -862,8 +869,7 @@ class Numerical : public BaseElement<Numerical> {
     Numerical& operator=(Numerical&& other);
     ~Numerical();
 
-    virtual bool operator==(const Numerical& other) const = 0;
-
+    virtual bool are_equal_impl(const Numerical& other) const = 0;
     virtual size_t hash_impl() const = 0;
     virtual void compute_repr_impl(std::stringstream& out) const = 0;
     virtual int compute_complexity_impl() const = 0;
@@ -891,8 +897,7 @@ class Boolean : public BaseElement<Boolean> {
     Boolean& operator=(Boolean&& other);
     ~Boolean();
 
-    virtual bool operator==(const Boolean& other) const = 0;
-
+    virtual bool are_equal_impl(const Boolean& other) const = 0;
     virtual size_t hash_impl() const = 0;
     virtual void compute_repr_impl(std::stringstream& out) const = 0;
     virtual int compute_complexity_impl() const = 0;
diff --git a/include/dlplan/core/elements/booleans/empty.h b/include/dlplan/core/elements/booleans/empty.h
index bcc5c64b..36fa506f 100644
--- a/include/dlplan/core/elements/booleans/empty.h
+++ b/include/dlplan/core/elements/booleans/empty.h
@@ -58,7 +58,7 @@ class EmptyBoolean : public Boolean {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Boolean& other) const override {
+    bool are_equal_impl(const Boolean& other) const override {
         if (typeid(*this) == typeid(other)) {
             const auto& other_derived = static_cast<const EmptyBoolean<T>&>(other);
             return m_is_static == other_derived.m_is_static
diff --git a/include/dlplan/core/elements/booleans/inclusion.h b/include/dlplan/core/elements/booleans/inclusion.h
index fccaa8dd..adc888c1 100644
--- a/include/dlplan/core/elements/booleans/inclusion.h
+++ b/include/dlplan/core/elements/booleans/inclusion.h
@@ -64,7 +64,7 @@ class InclusionBoolean : public Boolean {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Boolean& other) const override {
+    bool are_equal_impl(const Boolean& other) const override {
         if (typeid(*this) == typeid(other)) {
             const auto& other_derived = static_cast<const InclusionBoolean<T>&>(other);
             return m_is_static == other_derived.m_is_static
diff --git a/include/dlplan/core/elements/booleans/nullary.h b/include/dlplan/core/elements/booleans/nullary.h
index e23437b8..52a0fd22 100644
--- a/include/dlplan/core/elements/booleans/nullary.h
+++ b/include/dlplan/core/elements/booleans/nullary.h
@@ -34,7 +34,7 @@ class NullaryBoolean : public Boolean {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Boolean& other) const override;
+    bool are_equal_impl(const Boolean& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/concepts/all.h b/include/dlplan/core/elements/concepts/all.h
index 62ad8d26..bd70e802 100644
--- a/include/dlplan/core/elements/concepts/all.h
+++ b/include/dlplan/core/elements/concepts/all.h
@@ -34,7 +34,7 @@ class AllConcept : public Concept {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Concept& other) const override;
+    bool are_equal_impl(const Concept& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/concepts/and.h b/include/dlplan/core/elements/concepts/and.h
index be9121ca..1af77677 100644
--- a/include/dlplan/core/elements/concepts/and.h
+++ b/include/dlplan/core/elements/concepts/and.h
@@ -36,7 +36,7 @@ class AndConcept : public Concept {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Concept& other) const override;
+    bool are_equal_impl(const Concept& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/concepts/bot.h b/include/dlplan/core/elements/concepts/bot.h
index 97997d99..16fcaab8 100644
--- a/include/dlplan/core/elements/concepts/bot.h
+++ b/include/dlplan/core/elements/concepts/bot.h
@@ -29,7 +29,7 @@ class BotConcept : public Concept {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Concept& other) const override;
+    bool are_equal_impl(const Concept& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/concepts/diff.h b/include/dlplan/core/elements/concepts/diff.h
index b5168dcb..852b7f55 100644
--- a/include/dlplan/core/elements/concepts/diff.h
+++ b/include/dlplan/core/elements/concepts/diff.h
@@ -33,7 +33,7 @@ class DiffConcept : public Concept {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Concept& other) const override;
+    bool are_equal_impl(const Concept& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/concepts/equal.h b/include/dlplan/core/elements/concepts/equal.h
index 910dc236..41dcbb68 100644
--- a/include/dlplan/core/elements/concepts/equal.h
+++ b/include/dlplan/core/elements/concepts/equal.h
@@ -34,7 +34,7 @@ class EqualConcept : public Concept {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Concept& other) const override;
+    bool are_equal_impl(const Concept& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/concepts/not.h b/include/dlplan/core/elements/concepts/not.h
index cb0674ca..b1810f6b 100644
--- a/include/dlplan/core/elements/concepts/not.h
+++ b/include/dlplan/core/elements/concepts/not.h
@@ -33,7 +33,7 @@ class NotConcept : public Concept {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Concept& other) const override;
+    bool are_equal_impl(const Concept& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/concepts/one_of.h b/include/dlplan/core/elements/concepts/one_of.h
index a0140b5b..586a4e29 100644
--- a/include/dlplan/core/elements/concepts/one_of.h
+++ b/include/dlplan/core/elements/concepts/one_of.h
@@ -34,7 +34,7 @@ class OneOfConcept : public Concept {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Concept& other) const override;
+    bool are_equal_impl(const Concept& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/concepts/or.h b/include/dlplan/core/elements/concepts/or.h
index 76215e1d..d9568818 100644
--- a/include/dlplan/core/elements/concepts/or.h
+++ b/include/dlplan/core/elements/concepts/or.h
@@ -34,7 +34,7 @@ class OrConcept : public Concept {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Concept& other) const override;
+    bool are_equal_impl(const Concept& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/concepts/primitive.h b/include/dlplan/core/elements/concepts/primitive.h
index d4fa0bb3..6f9195ab 100644
--- a/include/dlplan/core/elements/concepts/primitive.h
+++ b/include/dlplan/core/elements/concepts/primitive.h
@@ -35,7 +35,7 @@ class PrimitiveConcept : public Concept {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Concept& other) const override;
+    bool are_equal_impl(const Concept& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/concepts/projection.h b/include/dlplan/core/elements/concepts/projection.h
index deacdcc8..72c76ca4 100644
--- a/include/dlplan/core/elements/concepts/projection.h
+++ b/include/dlplan/core/elements/concepts/projection.h
@@ -34,7 +34,7 @@ class ProjectionConcept : public Concept {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Concept& other) const override;
+    bool are_equal_impl(const Concept& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/concepts/some.h b/include/dlplan/core/elements/concepts/some.h
index 1200011d..4f3ea4e1 100644
--- a/include/dlplan/core/elements/concepts/some.h
+++ b/include/dlplan/core/elements/concepts/some.h
@@ -33,7 +33,7 @@ class SomeConcept : public Concept {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Concept& other) const override;
+    bool are_equal_impl(const Concept& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/concepts/subset.h b/include/dlplan/core/elements/concepts/subset.h
index 7d3ad3fc..fd418ff5 100644
--- a/include/dlplan/core/elements/concepts/subset.h
+++ b/include/dlplan/core/elements/concepts/subset.h
@@ -33,7 +33,7 @@ class SubsetConcept : public Concept {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Concept& other) const override;
+    bool are_equal_impl(const Concept& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/concepts/top.h b/include/dlplan/core/elements/concepts/top.h
index 58d3903c..3c604867 100644
--- a/include/dlplan/core/elements/concepts/top.h
+++ b/include/dlplan/core/elements/concepts/top.h
@@ -29,7 +29,7 @@ class TopConcept : public Concept {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Concept& other) const override;
+    bool are_equal_impl(const Concept& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/numericals/concept_distance.h b/include/dlplan/core/elements/numericals/concept_distance.h
index 61d933e8..727fccf6 100644
--- a/include/dlplan/core/elements/numericals/concept_distance.h
+++ b/include/dlplan/core/elements/numericals/concept_distance.h
@@ -34,7 +34,7 @@ class ConceptDistanceNumerical : public Numerical {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Numerical& other) const override;
+    bool are_equal_impl(const Numerical& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/numericals/count.h b/include/dlplan/core/elements/numericals/count.h
index da8b5cff..8dfe9fe2 100644
--- a/include/dlplan/core/elements/numericals/count.h
+++ b/include/dlplan/core/elements/numericals/count.h
@@ -63,7 +63,7 @@ class CountNumerical : public Numerical {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Numerical& other) const override {
+    bool are_equal_impl(const Numerical& other) const override {
         if (typeid(*this) == typeid(other)) {
             const auto& other_derived = static_cast<const CountNumerical&>(other);
             return m_is_static == other_derived.m_is_static
diff --git a/include/dlplan/core/elements/numericals/role_distance.h b/include/dlplan/core/elements/numericals/role_distance.h
index 2b83a14b..8f1e3113 100644
--- a/include/dlplan/core/elements/numericals/role_distance.h
+++ b/include/dlplan/core/elements/numericals/role_distance.h
@@ -34,7 +34,7 @@ class RoleDistanceNumerical : public Numerical {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Numerical& other) const override;
+    bool are_equal_impl(const Numerical& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/numericals/sum_concept_distance.h b/include/dlplan/core/elements/numericals/sum_concept_distance.h
index 5fb1f1aa..650c9048 100644
--- a/include/dlplan/core/elements/numericals/sum_concept_distance.h
+++ b/include/dlplan/core/elements/numericals/sum_concept_distance.h
@@ -34,7 +34,7 @@ class SumConceptDistanceNumerical : public Numerical {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Numerical& other) const override;
+    bool are_equal_impl(const Numerical& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/numericals/sum_role_distance.h b/include/dlplan/core/elements/numericals/sum_role_distance.h
index f73b145f..b9912bb5 100644
--- a/include/dlplan/core/elements/numericals/sum_role_distance.h
+++ b/include/dlplan/core/elements/numericals/sum_role_distance.h
@@ -35,7 +35,7 @@ class SumRoleDistanceNumerical : public Numerical {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Numerical& other) const override;
+    bool are_equal_impl(const Numerical& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/roles/and.h b/include/dlplan/core/elements/roles/and.h
index 51a74ef6..2285ed55 100644
--- a/include/dlplan/core/elements/roles/and.h
+++ b/include/dlplan/core/elements/roles/and.h
@@ -33,7 +33,7 @@ class AndRole : public Role {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Role& other) const override;
+    bool are_equal_impl(const Role& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/roles/compose.h b/include/dlplan/core/elements/roles/compose.h
index b9b01fad..d4145916 100644
--- a/include/dlplan/core/elements/roles/compose.h
+++ b/include/dlplan/core/elements/roles/compose.h
@@ -33,7 +33,7 @@ class ComposeRole : public Role {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Role& other) const override;
+    bool are_equal_impl(const Role& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/roles/diff.h b/include/dlplan/core/elements/roles/diff.h
index 83f11e97..80792e5a 100644
--- a/include/dlplan/core/elements/roles/diff.h
+++ b/include/dlplan/core/elements/roles/diff.h
@@ -35,7 +35,7 @@ class DiffRole : public Role {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Role& other) const override;
+    bool are_equal_impl(const Role& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/roles/identity.h b/include/dlplan/core/elements/roles/identity.h
index d41529eb..48fa3070 100644
--- a/include/dlplan/core/elements/roles/identity.h
+++ b/include/dlplan/core/elements/roles/identity.h
@@ -33,7 +33,7 @@ class IdentityRole : public Role {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Role& other) const override;
+    bool are_equal_impl(const Role& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/roles/inverse.h b/include/dlplan/core/elements/roles/inverse.h
index 57755480..0d75b3aa 100644
--- a/include/dlplan/core/elements/roles/inverse.h
+++ b/include/dlplan/core/elements/roles/inverse.h
@@ -33,7 +33,7 @@ class InverseRole : public Role {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Role& other) const override;
+    bool are_equal_impl(const Role& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/roles/not.h b/include/dlplan/core/elements/roles/not.h
index 5250fd8b..f243a524 100644
--- a/include/dlplan/core/elements/roles/not.h
+++ b/include/dlplan/core/elements/roles/not.h
@@ -33,7 +33,7 @@ class NotRole : public Role {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Role& other) const override;
+    bool are_equal_impl(const Role& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/roles/or.h b/include/dlplan/core/elements/roles/or.h
index ed467507..4041314c 100644
--- a/include/dlplan/core/elements/roles/or.h
+++ b/include/dlplan/core/elements/roles/or.h
@@ -33,7 +33,7 @@ class OrRole : public Role {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Role& other) const override;
+    bool are_equal_impl(const Role& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/roles/primitive.h b/include/dlplan/core/elements/roles/primitive.h
index 433234a3..6818e047 100644
--- a/include/dlplan/core/elements/roles/primitive.h
+++ b/include/dlplan/core/elements/roles/primitive.h
@@ -33,7 +33,7 @@ class PrimitiveRole : public Role {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Role& other) const override;
+    bool are_equal_impl(const Role& other) const override;
     size_t hash_impl() const override;
 
     RoleDenotation evaluate(const State& state) const override;
diff --git a/include/dlplan/core/elements/roles/restrict.h b/include/dlplan/core/elements/roles/restrict.h
index 4bbf494e..287fddc5 100644
--- a/include/dlplan/core/elements/roles/restrict.h
+++ b/include/dlplan/core/elements/roles/restrict.h
@@ -33,7 +33,7 @@ class RestrictRole : public Role {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Role& other) const override;
+    bool are_equal_impl(const Role& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/roles/top.h b/include/dlplan/core/elements/roles/top.h
index 421cf71a..6376edeb 100644
--- a/include/dlplan/core/elements/roles/top.h
+++ b/include/dlplan/core/elements/roles/top.h
@@ -29,7 +29,7 @@ class TopRole : public Role {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Role& other) const override;
+    bool are_equal_impl(const Role& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/roles/transitive_closure.h b/include/dlplan/core/elements/roles/transitive_closure.h
index c2de2126..4c553866 100644
--- a/include/dlplan/core/elements/roles/transitive_closure.h
+++ b/include/dlplan/core/elements/roles/transitive_closure.h
@@ -34,7 +34,7 @@ class TransitiveClosureRole : public Role {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Role& other) const override;
+    bool are_equal_impl(const Role& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/include/dlplan/core/elements/roles/transitive_reflexive_closure.h b/include/dlplan/core/elements/roles/transitive_reflexive_closure.h
index ce3267e2..15700333 100644
--- a/include/dlplan/core/elements/roles/transitive_reflexive_closure.h
+++ b/include/dlplan/core/elements/roles/transitive_reflexive_closure.h
@@ -32,7 +32,7 @@ class TransitiveReflexiveClosureRole : public Role {
     friend class dlplan::ReferenceCountedObjectFactory;
 
 public:
-    bool operator==(const Role& other) const override;
+    bool are_equal_impl(const Role& other) const override;
 
     size_t hash_impl() const override;
 
diff --git a/src/core/boolean.cpp b/src/core/boolean.cpp
index 60604591..90bcb30f 100644
--- a/src/core/boolean.cpp
+++ b/src/core/boolean.cpp
@@ -3,7 +3,7 @@
 
 namespace dlplan::core {
 Boolean::Boolean(std::shared_ptr<VocabularyInfo> vocabulary_info, ElementIndex index, bool is_static)
-    : BaseElement(vocabulary_info, index, is_static) {
+    : BaseElement(index, vocabulary_info, is_static) {
 }
 
 Boolean::Boolean(const Boolean& other) = default;
diff --git a/src/core/concept.cpp b/src/core/concept.cpp
index a1480be7..ecde168f 100644
--- a/src/core/concept.cpp
+++ b/src/core/concept.cpp
@@ -4,7 +4,7 @@
 namespace dlplan::core {
 
 Concept::Concept(std::shared_ptr<VocabularyInfo> vocabulary_info, ElementIndex index, bool is_static)
-    : BaseElement(vocabulary_info, index, is_static) {
+    : BaseElement(index, vocabulary_info, is_static) {
 }
 
 Concept::Concept(const Concept& other) = default;
diff --git a/src/core/elements/booleans/nullary.cpp b/src/core/elements/booleans/nullary.cpp
index b5b57ccd..77b2e1c6 100644
--- a/src/core/elements/booleans/nullary.cpp
+++ b/src/core/elements/booleans/nullary.cpp
@@ -41,7 +41,7 @@ NullaryBoolean::NullaryBoolean(ElementIndex index, std::shared_ptr<VocabularyInf
     }
 }
 
-bool NullaryBoolean::operator==(const Boolean& other) const {
+bool NullaryBoolean::are_equal_impl(const Boolean& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const NullaryBoolean&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/concepts/all.cpp b/src/core/elements/concepts/all.cpp
index 13650fbd..a64c0915 100644
--- a/src/core/elements/concepts/all.cpp
+++ b/src/core/elements/concepts/all.cpp
@@ -40,7 +40,7 @@ ConceptDenotations AllConcept::evaluate_impl(const States& states, DenotationsCa
 AllConcept::AllConcept(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabulary_info, std::shared_ptr<const Role> role, std::shared_ptr<const Concept> concept)
     : Concept(vocabulary_info, index, role->is_static() && concept->is_static()), m_role(role), m_concept(concept) { }
 
-bool AllConcept::operator==(const Concept& other) const {
+bool AllConcept::are_equal_impl(const Concept& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const AllConcept&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/concepts/and.cpp b/src/core/elements/concepts/and.cpp
index e7e95a62..ebd5ba7e 100644
--- a/src/core/elements/concepts/and.cpp
+++ b/src/core/elements/concepts/and.cpp
@@ -38,7 +38,7 @@ AndConcept::AndConcept(ElementIndex index, std::shared_ptr<VocabularyInfo> vocab
     m_concept_left(concept_1->get_index() < concept_2->get_index() ? concept_1 : concept_2),
     m_concept_right(concept_1->get_index() < concept_2->get_index() ? concept_2 : concept_1) { }
 
-bool AndConcept::operator==(const Concept& other) const {
+bool AndConcept::are_equal_impl(const Concept& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const AndConcept&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/concepts/bot.cpp b/src/core/elements/concepts/bot.cpp
index ebff12d8..3dadc3a1 100644
--- a/src/core/elements/concepts/bot.cpp
+++ b/src/core/elements/concepts/bot.cpp
@@ -19,7 +19,7 @@ ConceptDenotations BotConcept::evaluate_impl(const States& states, DenotationsCa
 BotConcept::BotConcept(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabulary_info)
 : Concept(vocabulary_info, index, true) { }
 
-bool BotConcept::operator==(const Concept& other) const {
+bool BotConcept::are_equal_impl(const Concept& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const BotConcept&>(other);
         return m_is_static == other_derived.m_is_static;
diff --git a/src/core/elements/concepts/diff.cpp b/src/core/elements/concepts/diff.cpp
index 74305b2f..f2865c95 100644
--- a/src/core/elements/concepts/diff.cpp
+++ b/src/core/elements/concepts/diff.cpp
@@ -35,7 +35,7 @@ ConceptDenotations DiffConcept::evaluate_impl(const States& states, DenotationsC
 DiffConcept::DiffConcept(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabulary_info, std::shared_ptr<const Concept> concept_1, std::shared_ptr<const Concept> concept_2)
     : Concept(vocabulary_info, index, concept_1->is_static() && concept_2->is_static()), m_concept_left(concept_1), m_concept_right(concept_2) { }
 
-bool DiffConcept::operator==(const Concept& other) const {
+bool DiffConcept::are_equal_impl(const Concept& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const DiffConcept&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/concepts/equal.cpp b/src/core/elements/concepts/equal.cpp
index e1785c84..73c4535b 100644
--- a/src/core/elements/concepts/equal.cpp
+++ b/src/core/elements/concepts/equal.cpp
@@ -43,7 +43,7 @@ EqualConcept::EqualConcept(ElementIndex index, std::shared_ptr<VocabularyInfo> v
     : Concept(vocabulary_info, index, role_left->is_static() && role_right->is_static()),
         m_role_left(role_left), m_role_right(role_right) { }
 
-bool EqualConcept::operator==(const Concept& other) const {
+bool EqualConcept::are_equal_impl(const Concept& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const EqualConcept&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/concepts/not.cpp b/src/core/elements/concepts/not.cpp
index aa9f15f9..86ee4c42 100644
--- a/src/core/elements/concepts/not.cpp
+++ b/src/core/elements/concepts/not.cpp
@@ -34,7 +34,7 @@ ConceptDenotations NotConcept::evaluate_impl(const States& states, DenotationsCa
 NotConcept::NotConcept(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabulary_info, std::shared_ptr<const Concept> concept)
     : Concept(vocabulary_info, index, concept->is_static()), m_concept(concept){ }
 
-bool NotConcept::operator==(const Concept& other) const {
+bool NotConcept::are_equal_impl(const Concept& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const NotConcept&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/concepts/one_of.cpp b/src/core/elements/concepts/one_of.cpp
index 0eda6ed2..9fa8dea5 100644
--- a/src/core/elements/concepts/one_of.cpp
+++ b/src/core/elements/concepts/one_of.cpp
@@ -40,7 +40,7 @@ ConceptDenotations OneOfConcept::evaluate_impl(const States& states, Denotations
 OneOfConcept::OneOfConcept(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabulary_info, const Constant& constant)
     : Concept(vocabulary_info, index, true), m_constant(constant) { }
 
-bool OneOfConcept::operator==(const Concept& other) const {
+bool OneOfConcept::are_equal_impl(const Concept& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const OneOfConcept&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/concepts/or.cpp b/src/core/elements/concepts/or.cpp
index 5ccfaf3a..7be034e8 100644
--- a/src/core/elements/concepts/or.cpp
+++ b/src/core/elements/concepts/or.cpp
@@ -38,7 +38,7 @@ OrConcept::OrConcept(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabul
     m_concept_left(concept_1->get_index() < concept_2->get_index() ? concept_1 : concept_2),
     m_concept_right(concept_1->get_index() < concept_2->get_index() ? concept_2 : concept_1) { }
 
-bool OrConcept::operator==(const Concept& other) const {
+bool OrConcept::are_equal_impl(const Concept& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const OrConcept&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/concepts/primitive.cpp b/src/core/elements/concepts/primitive.cpp
index 4d6befa8..dafdc536 100644
--- a/src/core/elements/concepts/primitive.cpp
+++ b/src/core/elements/concepts/primitive.cpp
@@ -50,7 +50,7 @@ PrimitiveConcept::PrimitiveConcept(ElementIndex index, std::shared_ptr<Vocabular
     }
 }
 
-bool PrimitiveConcept::operator==(const Concept& other) const {
+bool PrimitiveConcept::are_equal_impl(const Concept& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const PrimitiveConcept&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/concepts/projection.cpp b/src/core/elements/concepts/projection.cpp
index 441b7313..b291d30d 100644
--- a/src/core/elements/concepts/projection.cpp
+++ b/src/core/elements/concepts/projection.cpp
@@ -38,7 +38,7 @@ ProjectionConcept::ProjectionConcept(ElementIndex index, std::shared_ptr<Vocabul
     }
 }
 
-bool ProjectionConcept::operator==(const Concept& other) const {
+bool ProjectionConcept::are_equal_impl(const Concept& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const ProjectionConcept&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/concepts/some.cpp b/src/core/elements/concepts/some.cpp
index bbe4d574..03c20e30 100644
--- a/src/core/elements/concepts/some.cpp
+++ b/src/core/elements/concepts/some.cpp
@@ -39,7 +39,7 @@ ConceptDenotations SomeConcept::evaluate_impl(const States& states, DenotationsC
 SomeConcept::SomeConcept(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabulary_info, std::shared_ptr<const Role> role, std::shared_ptr<const Concept> concept)
     : Concept(vocabulary_info, index, role->is_static() && concept->is_static()), m_role(role), m_concept(concept) { }
 
-bool SomeConcept::operator==(const Concept& other) const {
+bool SomeConcept::are_equal_impl(const Concept& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const SomeConcept&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/concepts/subset.cpp b/src/core/elements/concepts/subset.cpp
index c462065d..47920a5b 100644
--- a/src/core/elements/concepts/subset.cpp
+++ b/src/core/elements/concepts/subset.cpp
@@ -39,7 +39,7 @@ ConceptDenotations SubsetConcept::evaluate_impl(const States& states, Denotation
 SubsetConcept::SubsetConcept(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabulary_info, std::shared_ptr<const Role> role_left, std::shared_ptr<const Role> role_right)
     : Concept(vocabulary_info, index, role_left->is_static() && role_right->is_static()), m_role_left(role_left), m_role_right(role_right) { }
 
-bool SubsetConcept::operator==(const Concept& other) const {
+bool SubsetConcept::are_equal_impl(const Concept& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const SubsetConcept&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/concepts/top.cpp b/src/core/elements/concepts/top.cpp
index d1a6daf0..ed2335f9 100644
--- a/src/core/elements/concepts/top.cpp
+++ b/src/core/elements/concepts/top.cpp
@@ -23,7 +23,7 @@ TopConcept::TopConcept(ElementIndex index, std::shared_ptr<VocabularyInfo> vocab
     : Concept(vocabulary_info, index, true) {
 }
 
-bool TopConcept::operator==(const Concept& other) const {
+bool TopConcept::are_equal_impl(const Concept& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const TopConcept&>(other);
         return m_is_static == other_derived.m_is_static;
diff --git a/src/core/elements/numericals/concept_distance.cpp b/src/core/elements/numericals/concept_distance.cpp
index b1de40b2..9759d9b3 100644
--- a/src/core/elements/numericals/concept_distance.cpp
+++ b/src/core/elements/numericals/concept_distance.cpp
@@ -61,7 +61,7 @@ ConceptDistanceNumerical::ConceptDistanceNumerical(ElementIndex index, std::shar
     : Numerical(vocabulary_info, index, concept_from->is_static() && role->is_static() && concept_to->is_static()),
         m_concept_from(concept_from), m_role(role), m_concept_to(concept_to) { }
 
-bool ConceptDistanceNumerical::operator==(const Numerical& other) const {
+bool ConceptDistanceNumerical::are_equal_impl(const Numerical& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const ConceptDistanceNumerical&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/numericals/role_distance.cpp b/src/core/elements/numericals/role_distance.cpp
index baea3a49..7e2f71e3 100644
--- a/src/core/elements/numericals/role_distance.cpp
+++ b/src/core/elements/numericals/role_distance.cpp
@@ -64,7 +64,7 @@ RoleDistanceNumerical::RoleDistanceNumerical(ElementIndex index, std::shared_ptr
     : Numerical(vocabulary_info, index, role_from->is_static() && role->is_static() && role_to->is_static()),
         m_role_from(role_from), m_role(role), m_role_to(role_to) { }
 
-bool RoleDistanceNumerical::operator==(const Numerical& other) const {
+bool RoleDistanceNumerical::are_equal_impl(const Numerical& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const RoleDistanceNumerical&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/numericals/sum_concept_distance.cpp b/src/core/elements/numericals/sum_concept_distance.cpp
index 94f5f714..79135c78 100644
--- a/src/core/elements/numericals/sum_concept_distance.cpp
+++ b/src/core/elements/numericals/sum_concept_distance.cpp
@@ -61,7 +61,7 @@ SumConceptDistanceNumerical::SumConceptDistanceNumerical(ElementIndex index, std
     : Numerical(vocabulary_info, index, concept_from->is_static() && role->is_static() && concept_to->is_static()),
         m_concept_from(concept_from), m_role(role), m_concept_to(concept_to) { }
 
-bool SumConceptDistanceNumerical::operator==(const Numerical& other) const {
+bool SumConceptDistanceNumerical::are_equal_impl(const Numerical& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const SumConceptDistanceNumerical&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/numericals/sum_role_distance.cpp b/src/core/elements/numericals/sum_role_distance.cpp
index af9c85a0..56dbca4d 100644
--- a/src/core/elements/numericals/sum_role_distance.cpp
+++ b/src/core/elements/numericals/sum_role_distance.cpp
@@ -66,7 +66,7 @@ SumRoleDistanceNumerical::SumRoleDistanceNumerical(ElementIndex index, std::shar
     : Numerical(vocabulary_info, index, role_from->is_static() && role->is_static() && role_to->is_static()),
         m_role_from(role_from), m_role(role), m_role_to(role_to) { }
 
-bool SumRoleDistanceNumerical::operator==(const Numerical& other) const {
+bool SumRoleDistanceNumerical::are_equal_impl(const Numerical& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const SumRoleDistanceNumerical&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/roles/and.cpp b/src/core/elements/roles/and.cpp
index d50a2490..4f9f0d57 100644
--- a/src/core/elements/roles/and.cpp
+++ b/src/core/elements/roles/and.cpp
@@ -38,7 +38,7 @@ AndRole::AndRole(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabulary_
     m_role_left(role_1->get_index() < role_2->get_index() ? role_1 : role_2),
     m_role_right(role_1->get_index() < role_2->get_index() ? role_2 : role_1) { }
 
-bool AndRole::operator==(const Role& other) const {
+bool AndRole::are_equal_impl(const Role& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const AndRole&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/roles/compose.cpp b/src/core/elements/roles/compose.cpp
index 789a6536..b7a606f1 100644
--- a/src/core/elements/roles/compose.cpp
+++ b/src/core/elements/roles/compose.cpp
@@ -43,7 +43,7 @@ RoleDenotations ComposeRole::evaluate_impl(const States& states, DenotationsCach
 ComposeRole::ComposeRole(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabulary_info, std::shared_ptr<const Role> role_left, std::shared_ptr<const Role> role_right)
     : Role(vocabulary_info, index, role_left->is_static() && role_right->is_static()), m_role_left(role_left), m_role_right(role_right)  { }
 
-bool ComposeRole::operator==(const Role& other) const {
+bool ComposeRole::are_equal_impl(const Role& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const ComposeRole&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/roles/diff.cpp b/src/core/elements/roles/diff.cpp
index b9a1e821..ff79a2f5 100644
--- a/src/core/elements/roles/diff.cpp
+++ b/src/core/elements/roles/diff.cpp
@@ -35,7 +35,7 @@ RoleDenotations DiffRole::evaluate_impl(const States& states, DenotationsCaches&
 DiffRole::DiffRole(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabulary_info, std::shared_ptr<const Role> role_left, std::shared_ptr<const Role> role_right)
     : Role(vocabulary_info, index, (role_left->is_static() && role_right->is_static())), m_role_left(role_left), m_role_right(role_right)  { }
 
-bool DiffRole::operator==(const Role& other) const {
+bool DiffRole::are_equal_impl(const Role& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const DiffRole&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/roles/identity.cpp b/src/core/elements/roles/identity.cpp
index 55922eab..ee33c61c 100644
--- a/src/core/elements/roles/identity.cpp
+++ b/src/core/elements/roles/identity.cpp
@@ -33,7 +33,7 @@ RoleDenotations IdentityRole::evaluate_impl(const States& states, DenotationsCac
 IdentityRole::IdentityRole(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabulary_info, std::shared_ptr<const Concept> concept)
     : Role(vocabulary_info, index, concept->is_static()), m_concept(concept) { }
 
-bool IdentityRole::operator==(const Role& other) const {
+bool IdentityRole::are_equal_impl(const Role& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const IdentityRole&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/roles/inverse.cpp b/src/core/elements/roles/inverse.cpp
index 89548cee..338351ef 100644
--- a/src/core/elements/roles/inverse.cpp
+++ b/src/core/elements/roles/inverse.cpp
@@ -33,7 +33,7 @@ RoleDenotations InverseRole::evaluate_impl(const States& states, DenotationsCach
 InverseRole::InverseRole(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabulary_info, std::shared_ptr<const Role> role)
     : Role(vocabulary_info, index, role->is_static()), m_role(role) { }
 
-bool InverseRole::operator==(const Role& other) const {
+bool InverseRole::are_equal_impl(const Role& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const InverseRole&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/roles/not.cpp b/src/core/elements/roles/not.cpp
index 0d731319..827b208e 100644
--- a/src/core/elements/roles/not.cpp
+++ b/src/core/elements/roles/not.cpp
@@ -32,7 +32,7 @@ RoleDenotations NotRole::evaluate_impl(const States& states, DenotationsCaches&
 NotRole::NotRole(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabulary_info, std::shared_ptr<const Role> role)
     : Role(vocabulary_info, index, role->is_static()), m_role(role) { }
 
-bool NotRole::operator==(const Role& other) const {
+bool NotRole::are_equal_impl(const Role& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const NotRole&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/roles/or.cpp b/src/core/elements/roles/or.cpp
index 4f41e404..58962744 100644
--- a/src/core/elements/roles/or.cpp
+++ b/src/core/elements/roles/or.cpp
@@ -37,7 +37,7 @@ OrRole::OrRole(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabulary_in
     m_role_left(role_1->get_index() < role_2->get_index() ? role_1 : role_2),
     m_role_right(role_1->get_index() < role_2->get_index() ? role_2 : role_1) { }
 
-bool OrRole::operator==(const Role& other) const {
+bool OrRole::are_equal_impl(const Role& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const OrRole&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/roles/primitive.cpp b/src/core/elements/roles/primitive.cpp
index 3e50bfda..84a2f99a 100644
--- a/src/core/elements/roles/primitive.cpp
+++ b/src/core/elements/roles/primitive.cpp
@@ -56,7 +56,7 @@ PrimitiveRole::PrimitiveRole(ElementIndex index, std::shared_ptr<VocabularyInfo>
     }
 }
 
-bool PrimitiveRole::operator==(const Role& other) const {
+bool PrimitiveRole::are_equal_impl(const Role& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const PrimitiveRole&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/roles/restrict.cpp b/src/core/elements/roles/restrict.cpp
index 5e10b20c..57eeba02 100644
--- a/src/core/elements/roles/restrict.cpp
+++ b/src/core/elements/roles/restrict.cpp
@@ -39,7 +39,7 @@ RoleDenotations RestrictRole::evaluate_impl(const States& states, DenotationsCac
 RestrictRole::RestrictRole(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabulary_info, std::shared_ptr<const Role> role, std::shared_ptr<const Concept> concept)
 : Role(vocabulary_info, index, role->is_static() && concept->is_static()), m_role(role), m_concept(concept) { }
 
-bool RestrictRole::operator==(const Role& other) const {
+bool RestrictRole::are_equal_impl(const Role& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const RestrictRole&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/roles/top.cpp b/src/core/elements/roles/top.cpp
index 09f927c0..c22276dc 100644
--- a/src/core/elements/roles/top.cpp
+++ b/src/core/elements/roles/top.cpp
@@ -22,7 +22,7 @@ RoleDenotations TopRole::evaluate_impl(const States& states, DenotationsCaches&
 TopRole::TopRole(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabulary_info)
     : Role(vocabulary_info, index, true) { }
 
-bool TopRole::operator==(const Role& other) const {
+bool TopRole::are_equal_impl(const Role& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const TopRole&>(other);
         return m_is_static == other_derived.m_is_static;
diff --git a/src/core/elements/roles/transitive_closure.cpp b/src/core/elements/roles/transitive_closure.cpp
index 37641d55..848f22b8 100644
--- a/src/core/elements/roles/transitive_closure.cpp
+++ b/src/core/elements/roles/transitive_closure.cpp
@@ -45,7 +45,7 @@ RoleDenotations TransitiveClosureRole::evaluate_impl(const States& states, Denot
 TransitiveClosureRole::TransitiveClosureRole(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabulary_info, std::shared_ptr<const Role> role)
     : Role(vocabulary_info, index, role->is_static()), m_role(role) { }
 
-bool TransitiveClosureRole::operator==(const Role& other) const {
+bool TransitiveClosureRole::are_equal_impl(const Role& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const TransitiveClosureRole&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/elements/roles/transitive_reflexive_closure.cpp b/src/core/elements/roles/transitive_reflexive_closure.cpp
index 87f739f1..28583220 100644
--- a/src/core/elements/roles/transitive_reflexive_closure.cpp
+++ b/src/core/elements/roles/transitive_reflexive_closure.cpp
@@ -50,7 +50,7 @@ RoleDenotations TransitiveReflexiveClosureRole::evaluate_impl(const States& stat
 TransitiveReflexiveClosureRole::TransitiveReflexiveClosureRole(ElementIndex index, std::shared_ptr<VocabularyInfo> vocabulary_info, std::shared_ptr<const Role> role)
     : Role(vocabulary_info, index, role->is_static()), m_role(role) { }
 
-bool TransitiveReflexiveClosureRole::operator==(const Role& other) const {
+bool TransitiveReflexiveClosureRole::are_equal_impl(const Role& other) const {
     if (typeid(*this) == typeid(other)) {
         const auto& other_derived = static_cast<const TransitiveReflexiveClosureRole&>(other);
         return m_is_static == other_derived.m_is_static
diff --git a/src/core/numerical.cpp b/src/core/numerical.cpp
index 9d927fb6..53563aa9 100644
--- a/src/core/numerical.cpp
+++ b/src/core/numerical.cpp
@@ -4,7 +4,7 @@
 namespace dlplan::core {
 
 Numerical::Numerical(std::shared_ptr<VocabularyInfo> vocabulary_info, ElementIndex index, bool is_static)
-    : BaseElement(vocabulary_info, index, is_static) {
+    : BaseElement(index, vocabulary_info, is_static) {
 }
 
 Numerical::Numerical(const Numerical& other) = default;
diff --git a/src/core/role.cpp b/src/core/role.cpp
index 060c1df7..2f9d2cd3 100644
--- a/src/core/role.cpp
+++ b/src/core/role.cpp
@@ -4,7 +4,7 @@
 namespace dlplan::core {
 
 Role::Role(std::shared_ptr<VocabularyInfo> vocabulary_info, ElementIndex index, bool is_static)
-    : BaseElement(vocabulary_info, index, is_static) {
+    : BaseElement(index, vocabulary_info, is_static) {
 }
 
 Role::Role(const Role& other) = default;