diff --git a/include/core.hpp b/include/core.hpp
index e8e97bc..ee1e536 100644
--- a/include/core.hpp
+++ b/include/core.hpp
@@ -258,7 +258,7 @@ namespace riddle
      *
      * @param disjuncts The disjuncts.
      */
-    virtual void new_disjunction(std::vector<std::unique_ptr<riddle::conjunction>> &&disjuncts) = 0;
+    virtual void new_disjunction(std::vector<std::unique_ptr<conjunction>> &&disjuncts) = 0;
 
     /**
      * @brief Create a new fact or goal atom with the given predicate and arguments.
@@ -396,7 +396,7 @@ namespace riddle
    * @return true If the expression is a boolean.
    * @return false If the expression is not a boolean.
    */
-  [[nodiscard]] inline bool is_bool(const riddle::item &x) noexcept { return &x.get_type().get_scope().get_core().get_bool_type() == &x.get_type(); }
+  [[nodiscard]] inline bool is_bool(const item &x) noexcept { return &x.get_type().get_scope().get_core().get_bool_type() == &x.get_type(); }
   /**
    * @brief Determine if the expression is an integer.
    *
@@ -404,7 +404,7 @@ namespace riddle
    * @return true If the expression is an integer.
    * @return false If the expression is not an integer.
    */
-  [[nodiscard]] inline bool is_int(const riddle::item &x) noexcept { return &x.get_type().get_scope().get_core().get_int_type() == &x.get_type(); }
+  [[nodiscard]] inline bool is_int(const item &x) noexcept { return &x.get_type().get_scope().get_core().get_int_type() == &x.get_type(); }
   /**
    * @brief Determine if the expression is a real.
    *
@@ -412,7 +412,7 @@ namespace riddle
    * @return true If the expression is a real.
    * @return false If the expression is not a real.
    */
-  [[nodiscard]] inline bool is_real(const riddle::item &x) noexcept { return &x.get_type().get_scope().get_core().get_real_type() == &x.get_type(); }
+  [[nodiscard]] inline bool is_real(const item &x) noexcept { return &x.get_type().get_scope().get_core().get_real_type() == &x.get_type(); }
   /**
    * @brief Determine if the expression is a time.
    *
@@ -420,7 +420,7 @@ namespace riddle
    * @return true If the expression is a time.
    * @return false If the expression is not a time.
    */
-  [[nodiscard]] inline bool is_time(const riddle::item &x) noexcept { return &x.get_type().get_scope().get_core().get_time_type() == &x.get_type(); }
+  [[nodiscard]] inline bool is_time(const item &x) noexcept { return &x.get_type().get_scope().get_core().get_time_type() == &x.get_type(); }
   /**
    * @brief Determine if the expression is an arithmetic value.
    *
@@ -428,7 +428,7 @@ namespace riddle
    * @return true If the expression is an arithmetic value.
    * @return false If the expression is not an arithmetic value.
    */
-  [[nodiscard]] inline bool is_arith(const riddle::item &x) noexcept { return is_int(x) || is_real(x) || is_time(x); }
+  [[nodiscard]] inline bool is_arith(const item &x) noexcept { return is_int(x) || is_real(x) || is_time(x); }
   /**
    * @brief Determine if the expression is a string.
    *
@@ -436,7 +436,7 @@ namespace riddle
    * @return true If the expression is a string.
    * @return false If the expression is not a string.
    */
-  [[nodiscard]] inline bool is_string(const riddle::item &x) noexcept { return &x.get_type().get_scope().get_core().get_string_type() == &x.get_type(); }
+  [[nodiscard]] inline bool is_string(const item &x) noexcept { return &x.get_type().get_scope().get_core().get_string_type() == &x.get_type(); }
   /**
    * @brief Determine if the expression is an enumeration.
    *
@@ -444,7 +444,7 @@ namespace riddle
    * @return true If the expression is an enumeration.
    * @return false If the expression is not an enumeration.
    */
-  [[nodiscard]] inline bool is_enum(const riddle::item &x) noexcept { return dynamic_cast<const enum_item *>(&x) != nullptr; }
+  [[nodiscard]] inline bool is_enum(const item &x) noexcept { return dynamic_cast<const enum_item *>(&x) != nullptr; }
   /**
    * @brief Determine if the expression is a constant.
    *
@@ -457,7 +457,7 @@ namespace riddle
    * @return true If the expression is a constant.
    * @return false If the expression is not a constant.
    */
-  [[nodiscard]] inline bool is_constant(const riddle::item &x) noexcept
+  [[nodiscard]] inline bool is_constant(const item &x) noexcept
   {
     if (is_bool(x)) // the expression is a boolean..
       return x.get_type().get_scope().get_core().bool_value(static_cast<const bool_item &>(x)) != utils::Undefined;
diff --git a/include/item.hpp b/include/item.hpp
index 6cb7cf3..7cb0d0f 100644
--- a/include/item.hpp
+++ b/include/item.hpp
@@ -115,12 +115,43 @@ namespace riddle
     atom(predicate &t, bool is_fact, const utils::lit &sigma, std::map<std::string, std::shared_ptr<item>> &&args = {});
     virtual ~atom() = default;
 
+    /**
+     * @brief Checks if the item is a fact.
+     *
+     * @return true if the item is a fact, false otherwise.
+     */
     [[nodiscard]] bool is_fact() const { return fact; }
+    /**
+     * @brief Get the status of the atom as a literal.
+     *
+     * @return const utils::lit& the status of the atom.
+     * @note the literal assumes the following values:
+     * - `True` if the atom is `Active`.
+     * - `False` if the atom is `Unified`.
+     * - `Undefined` if the atom is `Inactive`.
+     */
     [[nodiscard]] utils::lit &get_sigma() { return sigma; }
+    /**
+     * @brief Get the status of the atom as a literal.
+     *
+     * @return const utils::lit& the status of the atom.
+     * @note the literal assumes the following values:
+     * - `True` if the atom is `Active`.
+     * - `False` if the atom is `Unified`.
+     * - `Undefined` if the atom is `Inactive`.
+     */
     [[nodiscard]] const utils::lit &get_sigma() const { return sigma; }
 
   private:
     bool fact;        // whether the atom is a fact or a goal..
     utils::lit sigma; // the literal indicating the status of the atom (i.e., true if active, false if unified, undefined if inactive)..
   };
+
+  /**
+   * @brief Gets the unique identifier of the given item.
+   *
+   * @param f the item to get the unique identifier of.
+   * @return uintptr_t the unique identifier of the given item.
+   */
+  inline uintptr_t get_id(const item &itm) noexcept { return reinterpret_cast<uintptr_t>(&itm); }
 } // namespace riddle