diff --git a/src/libs/db/postgresql_connector/include/eedb/db/pg/PgCategories.hpp b/src/libs/db/postgresql_connector/include/eedb/db/pg/PgCategories.hpp
index 13cdcf6..c70039e 100644
--- a/src/libs/db/postgresql_connector/include/eedb/db/pg/PgCategories.hpp
+++ b/src/libs/db/postgresql_connector/include/eedb/db/pg/PgCategories.hpp
@@ -9,12 +9,11 @@ class PgConnection;
 }
 
 namespace eedb {
-class PgCategory;
 
 class PgCategories : public Categories {
     // Categories interface
   public:
-    PgCategories(std::vector<std::unique_ptr<eedb::PgCategory> > &&data);
+    PgCategories(std::vector<std::unique_ptr<eedb::Category> > &&data);
 
     long size() const override;
 
diff --git a/src/libs/db/postgresql_connector/mock/include/eedb/mock/db/pg/CategoryMock.hpp b/src/libs/db/postgresql_connector/mock/include/eedb/mock/db/pg/CategoryMock.hpp
index d5005c2..8dc8be8 100644
--- a/src/libs/db/postgresql_connector/mock/include/eedb/mock/db/pg/CategoryMock.hpp
+++ b/src/libs/db/postgresql_connector/mock/include/eedb/mock/db/pg/CategoryMock.hpp
@@ -4,18 +4,19 @@
 #ifndef CATEGORYMOCK_HPP
 #define CATEGORYMOCK_HPP
 
+#include <eedb/db/Category.hpp>
 #include <gmock/gmock.h>
-#include "././eedb/db/Category.hpp"
 
 namespace eedb {
 
-class CategoryMock : public Category
-{
-public:
-    MOCK_CONST_METHOD0(parent, Category*());
+class CategoryMock : public Category {
+  public:
+    MOCK_CONST_METHOD0(display_name, std::string_view());
+    MOCK_CONST_METHOD0(parent, Category *());
+    MOCK_CONST_METHOD2(create, std::unique_ptr< Category >(std::string, std::string));
+    MOCK_CONST_METHOD0(children, std::unique_ptr< Categories >());
 };
 
 } // namespace eedb
 
 #endif // CATEGORYMOCK_HPP
-
diff --git a/src/libs/db/postgresql_connector/src/data/PgCategories.cpp b/src/libs/db/postgresql_connector/src/data/PgCategories.cpp
index 4828c78..6de235e 100644
--- a/src/libs/db/postgresql_connector/src/data/PgCategories.cpp
+++ b/src/libs/db/postgresql_connector/src/data/PgCategories.cpp
@@ -12,7 +12,7 @@ namespace eedb {
 struct PgCategories::PgCategoriesPriv {
   private:
     static auto getTransform() {
-        return [](auto & cat) { return static_cast< Category * >(cat.get()); };
+        return [](auto & cat) { return cat.get(); };
     }
 
     auto tBegin() {
@@ -24,7 +24,7 @@ struct PgCategories::PgCategoriesPriv {
     }
 
   public:
-    PgCategoriesPriv(std::vector< std::unique_ptr< PgCategory > > && data) : _cache{std::move(data)} {}
+    PgCategoriesPriv(std::vector< std::unique_ptr< Category > > && data) : _cache{std::move(data)} {}
 
     auto begin() {
         return Categories::Iterable{tBegin()};
@@ -35,10 +35,10 @@ struct PgCategories::PgCategoriesPriv {
     }
 
   private:
-    std::vector< std::unique_ptr< PgCategory > > _cache;
+    std::vector< std::unique_ptr< Category > > _cache;
 };
 
-PgCategories::PgCategories(std::vector< std::unique_ptr< PgCategory > > && data)
+PgCategories::PgCategories(std::vector< std::unique_ptr< Category > > && data)
  : _priv{spimpl::make_unique_impl< PgCategoriesPriv >(std::move(data))} {}
 
 long PgCategories::size() const {
diff --git a/src/libs/db/postgresql_connector/src/data/PgCategory.cpp b/src/libs/db/postgresql_connector/src/data/PgCategory.cpp
index 4db0290..2573d03 100644
--- a/src/libs/db/postgresql_connector/src/data/PgCategory.cpp
+++ b/src/libs/db/postgresql_connector/src/data/PgCategory.cpp
@@ -69,7 +69,7 @@ struct PgCategory::PgCategoryPrivate {
     }
 
     auto categories() const {
-        std::vector< std::unique_ptr< PgCategory > > children;
+        std::vector< std::unique_ptr< Category > > children;
         children.reserve(100);
         for(auto & category_row : _db(select(columns()).from(table_list()).where(parent_match()))) {
             auto priv = spimpl::make_impl< PgCategoryPrivate >(_db, _owner, _self);
diff --git a/src/libs/db/postgresql_connector/src/data/PgItem.cpp b/src/libs/db/postgresql_connector/src/data/PgItem.cpp
index e69de29..17984a1 100644
--- a/src/libs/db/postgresql_connector/src/data/PgItem.cpp
+++ b/src/libs/db/postgresql_connector/src/data/PgItem.cpp
@@ -0,0 +1 @@
+#include <eedb/Value.hpp>
diff --git a/src/libs/db/postgresql_connector/src/data/PgItem.hpp b/src/libs/db/postgresql_connector/src/data/PgItem.hpp
index e69de29..e85a6e2 100644
--- a/src/libs/db/postgresql_connector/src/data/PgItem.hpp
+++ b/src/libs/db/postgresql_connector/src/data/PgItem.hpp
@@ -0,0 +1,3 @@
+#pragma once
+
+#include <eedb/db/Item.hpp>
diff --git a/src/libs/db/postgresql_connector/test/test_eedb_data_PgCategories.cpp b/src/libs/db/postgresql_connector/test/test_eedb_data_PgCategories.cpp
index 34648f3..4ab996c 100644
--- a/src/libs/db/postgresql_connector/test/test_eedb_data_PgCategories.cpp
+++ b/src/libs/db/postgresql_connector/test/test_eedb_data_PgCategories.cpp
@@ -2,21 +2,33 @@
 
 #include "DbTestBase.hpp"
 
+#include <eedb/mock/db/pg/CategoryMock.hpp>
+#include <utils/UniquePtrMockWrapper.hpp>
+
 class PgCategoriesTest : public DbTestBase< PgCategoriesTest > {
   public:
     PgCategoriesTest() {
         db().native()->start_transaction();
 
-//        sut = std::make_unique< eedb::PgCategories >();
+
+        //sut = std::make_unique< eedb::PgCategories >(_categories);
     }
 
     ~PgCategoriesTest() {
         db().native()->rollback_transaction(false);
     }
 
-  private:
+  protected:
+    std::vector< UniquePtrMockWrapper< eedb::CategoryMock > > _categories;
+
     std::unique_ptr< eedb::PgCategories > sut;
 };
 
 template <>
 std::unique_ptr< PgTestDatabasePrepare > DbTestBase< PgCategoriesTest >::_test_db = {};
+
+//TEST_F(PgCategoriesTest, size) {
+//    EXPECT_EQ(sut->size(), 4);
+//}
+
+//TEST_F(PgCategoriesTest, )
diff --git a/src/libs/db/postgresql_connector/test/test_eedb_data_PgUser.cpp b/src/libs/db/postgresql_connector/test/test_eedb_data_PgUser.cpp
index 04441e8..22e82f4 100644
--- a/src/libs/db/postgresql_connector/test/test_eedb_data_PgUser.cpp
+++ b/src/libs/db/postgresql_connector/test/test_eedb_data_PgUser.cpp
@@ -67,4 +67,4 @@ TEST_F(PgUserTest, getIdentities) {
     EXPECT_TRUE(sut->authIdentities().byProvider("loginname"));
 }
 
-TEST_F(PgUserTest, getTokens) {}
+TEST_F(PgUserTest, getConfig) {}
diff --git a/src/libs/eedb/include/eedb/Parameter.hpp b/src/libs/eedb/include/eedb/Parameter.hpp
new file mode 100644
index 0000000..7514cb8
--- /dev/null
+++ b/src/libs/eedb/include/eedb/Parameter.hpp
@@ -0,0 +1,13 @@
+#pragma once
+
+#include <optional>
+
+#include <eedb/Unit.hpp>
+
+namespace eedb {
+
+class Parameter {
+  public:
+    std::optional< Unit > unit() const {}
+};
+} // namespace eedb
diff --git a/src/libs/eedb/include/eedb/db/Unit.hpp b/src/libs/eedb/include/eedb/Unit.hpp
similarity index 61%
rename from src/libs/eedb/include/eedb/db/Unit.hpp
rename to src/libs/eedb/include/eedb/Unit.hpp
index 75561ee..e824e63 100644
--- a/src/libs/eedb/include/eedb/db/Unit.hpp
+++ b/src/libs/eedb/include/eedb/Unit.hpp
@@ -4,15 +4,13 @@
 
 namespace eedb {
 
-class Units {
-  public:
-    virtual ~Units() = default;
-};
-
+/**
+ * @brief The Unit class
+ */
 class Unit {
   public:
+
     std::string_view name() const;
-    Unit toBase() const;
 };
 
 } // namespace eedb
diff --git a/src/libs/eedb/include/eedb/Value.hpp b/src/libs/eedb/include/eedb/Value.hpp
new file mode 100644
index 0000000..20812a2
--- /dev/null
+++ b/src/libs/eedb/include/eedb/Value.hpp
@@ -0,0 +1,76 @@
+#pragma once
+
+#include <optional>
+#include <string>
+#include <variant>
+
+#include <eedb/Parameter.hpp>
+
+namespace eedb {
+
+class Value;
+
+/**
+ * @brief The Values class
+ */
+class Values {
+  public:
+    virtual ~Values() = default;
+};
+
+class NumericValue {
+  public:
+    explicit NumericValue(double t) : _value{t} {}
+
+    std::string to_string() const {
+        return std::to_string(_value);
+    }
+
+    double value() const {
+        return _value;
+    }
+
+  private:
+    double _value;
+};
+
+class TextValue {
+  public:
+    explicit TextValue(std::string_view value) : _value{value} {}
+
+    std::string to_string() const {
+        return _value;
+    }
+
+    std::string_view value() const {
+        return _value;
+    }
+
+  private:
+    std::string _value;
+};
+
+/**
+ * @brief The Value class
+ */
+class Value {
+  public:
+    enum class Type { Numeric, Text };
+
+    /**
+     * @brief to_string
+     * @return returns value as string
+     */
+    std::string to_string() const;
+
+    Type type() const {
+        return Type::Numeric;
+    }
+
+    std::optional< Parameter > parameter() const {}
+
+  private:
+    std::variant< TextValue, NumericValue > _value;
+};
+
+} // namespace eedb
diff --git a/src/libs/eedb/include/eedb/db/Item.hpp b/src/libs/eedb/include/eedb/db/Item.hpp
index dae2f39..0100667 100644
--- a/src/libs/eedb/include/eedb/db/Item.hpp
+++ b/src/libs/eedb/include/eedb/db/Item.hpp
@@ -11,7 +11,8 @@ class Category;
 class Item;
 class Items;
 class Values;
-class Units;
+class Parameters;
+
 /**
  * @brief The ItemQueryFilters class
  */
@@ -58,6 +59,12 @@ class Items {
      */
     virtual long size() const = 0;
 
+    /**
+     * @brief commonParameters
+     * @return
+     */
+    virtual Parameters commonParameters() const = 0;
+
     /**
      * @brief begin
      * @return
@@ -78,8 +85,22 @@ class Item {
   public:
     virtual ~Item() = default;
 
+    /**
+     * @brief displayName
+     * @return
+     */
     virtual std::string_view displayName() const = 0;
 
-    virtual Values & values() const = 0;
+    /**
+     * @brief assignedUnits
+     * @return
+     */
+    virtual Values assignedUnits() const = 0;
+
+    /**
+     * @brief assignedParameters
+     * @return
+     */
+    virtual Parameters assignedParameters() const = 0;
 };
 } // namespace eedb
diff --git a/src/libs/eedb/include/eedb/db/Value.hpp b/src/libs/eedb/include/eedb/db/Value.hpp
deleted file mode 100644
index a86ba85..0000000
--- a/src/libs/eedb/include/eedb/db/Value.hpp
+++ /dev/null
@@ -1,16 +0,0 @@
-#pragma once
-
-#include <variant>
-
-namespace eedb {
-class Value;
-class Values {
-  public:
-    virtual ~Values() = default;
-
-};
-
-class Value {
-  public:
-};
-} // namespace eedb