Minor changes in Section 4.1

For better readability:

4 Generic _Core _Metamodel

4.1 _Generic Core _Elements

From ... elements of the ArchiMate language is presented... to ... elements of the ArchiMate _Core _language is presented ...

From ... the elements of the different architecture layers... to ... the elements of the different architecture _core _layers

From Figure 4: Hierarchy of Behavior and Structure Elements to Figure 4: Hierarchy of Behavior and Structure Elements_ in the Core Layers_

From This generic metamodel fragment consists ... to This generic _core _metamodel fragment...

From Figure 5: Behavior and Structure Elements Metamodel to Figure 5: Generic Core Elements Metamodel