+ void check_concurrency() const;
+
+ /**
+ * @brief Auxiliary method to create a new Element which links a variable to a constraint
+ *
+ * @param cnst Constraint (resource)
+ * @param var Variable (action)
+ * @param consumption_weight how much of the resource is used for each unit of the action
+ * @return A reference to the new element
+ */
+ Element& expand_create_elem(Constraint* cnst, Variable* var, double consumption_weight);
+ /**
+ * @brief Increments the element usage
+ *
+ * @param elem Element linking variable/action to resource
+ * @param cnst Constraint (resource)
+ * @param consumption_weight how much of the resource is used for each unit of the action
+ * @return elem itself
+ */
+ Element& expand_add_to_elem(Element& elem, const Constraint* cnst, double consumption_weight) const;