The most obvious of the GOPPRR metatypes is object. The main elements of a diagram in your modeling language will generally be objects. In our case, our domain concept of Person falls into this category. Start the Object Tool (as shown in Figure 3-1) by pressing Object Tool toolbar button or selecting Metamodel | Object Tool in the MetaEdit+ launcher.

Start creating the Person type by typing its name (i.e. ‘Person’) into the text field at the top of the Object Tool. Also make sure that the project for your object is ‘Family Tree’ (if not, you can change it by selecting Object | Set Default Project... and choosing ‘Family Tree’ from the list that appears).

Next, we need to state what information can be stored for each Person. In GOPPRR each slot for storing information is called a property. To add a property to our Person object, move the mouse over the area of the Properties list in the Object Tool and press the right mouse button. From the pop-up menu that opens, select Add Property... to add a property. As there are no property types defined yet, MetaEdit+ automatically chooses to create a new property type (if there are already some types, you must choose ‘New Property Type’ from the dialog that opens). This opens a Property Tool for defining a new property type (shown in Figure 3-2).

In the Property Tool, enter the name for the property (‘First name’). The other values are correct by default in this case, so you can proceed by pressing the Save button in the toolbar. As this is the first time you have generated a type in this session, MetaEdit+ will run a check on all types in the database. As there are many types in the demo repository, this will take several seconds – but only for this first time. If you see a dialog asking “Do you really want to add the property First name to Person?’, press Yes to accept the addition and accept ‘First name’ as local name in the following dialog. Close the Property Tool if it did not close automatically (it depends on your settings) and go back to the Object Tool. You see now how the created property appears in the Properties list of the Person object (as shown in Figure 3-3).

Next we will create the ‘Family name’ property. In the Object Tool, again move the mouse over the Properties list and press the right mouse button to open the pop-up menu. Choose Add Property... from there, and select ‘New Property Type’. In the Property Tool, enter ‘Family name’ in the Name field.

The Widget list in the Property Tool allows us to select how users will enter values of this property. As there will be several Persons with the same Family Name, it would be useful if the user could select these previously entered values from a pull-down list, into which each new name will be added. The widget for this is called an Editable List: choose it from the possible widget types from the Widget list. Press Save and close the Property Tool if it is not automatically closed.

Your Object Tool should now look like Figure 3-4. Press Save in the toolbar (answer ‘Yes’ if MetaEdit+ asks if a default dialog for the new object should be generated). You have now completed the definition of the Person concept.