We now have all the metamodel fragments we need for the first version of our Family Tree modeling language, so it could be a good time to commit again. What we need to do now is to somehow assemble these fragments into a complete modeling language. However, let us first consider again what we are about to do. What is our Family Tree modeling language actually like? It is a simple diagram notation for drawing family trees. This means that we should now be able to define the diagram type of the Family Tree modeling language.

In GOPPRR the metatype graph corresponds to a diagram type. To create a new diagram type, we must create a new graph type with the Graph Tool. Open the Graph Tool by pressing Graph Tool toolbar button or selecting Metamodel | Graph Tool in the MetaEdit+ launcher.

First, enter the name for our modeling language (‘Family Tree’) in the Name field. Go to the Properties list, press the right mouse button and select Add Property... from the pop-up menu. This time we do not want to create a completely new property type, instead we shall reuse the existing ‘Family name’ property as a name for our diagram; the name of each diagram can thus be a family name. So, choose ‘Family name’ from the list of possible properties (if asked, accept the default local name proposed by MetaEdit+). Your Graph Tool should now look similar to Figure 3-13.

Go next to the Types page on the Graph Tool tab view. This is where you choose the types you want to use in your modeling language. Go to the Relationships list, press the right mouse button and select Add... from the pop-up menu. From the list that opens, choose ‘Family’ and press OK. The ‘Family’ relationship now appears in the Relationships list. Similarly, add ‘Parent’ and ‘Child’ roles to the Roles list (multiple selection is allowed) and ‘Person’ to the Objects list. Your Graph Tool should now look like Figure 3-14.

Go to the Bindings page in the tab view. Here you will create the bindings that actually connect your metamodel fragments as a complete modeling language specification. Go first to the Relationships list, press the right mouse button, select Add... from the pop-up menu and then ‘Family’ from the list.

Make sure that ‘Family’ is selected in the Relationships list. Go to the Roles list and press the right mouse button there. Choose Add... and then select ‘Parent’ from the list. Now, with both ‘Family’ and ‘Parent’ selected, add ‘Person’ to the Objects list (skip the Ports list). You have now created a part of the binding that says: “The Parent role in a Family relationship must connect to a Person object”.

As there are always two Parents for a Person, add another Parent role similarly and add Person for it in the Objects list. The Graph Tool should now look like Figure 3-15.

In addition to a Parent role, there is also a Child role in the Family relationship. To create it, move the mouse over the Roles list, press the right mouse button, choose Add... from the pop-up menu and then ‘Child’ from the list of available roles. As the Objects list now becomes blank, go there and add the Person object again. We have now created the part of a binding that says: “The Child role in a Family relationship must connect to a Person object”.

As the problem domain specification and our metamodel implies, there are certain constraints that limit the set of possible Family combinations: there can be two and only two Parents but zero to many Children in a Family. In GOPPRR, these constraints are handled by roles. The requirement for two Parents is already taken care of with two separate Parent roles, but the cardinality of ‘zero to many Children’ must still be set. Select the Child role from the Roles list, press the right mouse button and choose Cardinality... from the pop-up menu. In the Cardinality Dialog that appears (Figure 3-16), set the Minimum to 0 and the Maximum to N and press OK.

Your Graph Tool should now look like Figure 3-17. Press Save and Close to save the graph definition and close the Graph Tool (if asked, accept the generation of the default dialog). Also remember to commit your work again.

Congratulations! You have now completed the first version of our Family Tree modeling language. Working with the Family Tree Modeling Language

So far we have been exploring the metamodeling tools of MetaEdit+. In addition to these, MetaEdit+ also offers a fully functional CASE environment for using the modeling languages we have created. Let us now familiarize ourselves with the CASE tool functionality by trying out the Family Tree modeling language.