The next things we want to add to our diagram are the relationships between parents and children. There are two ways to draw relationships. The first way is applicable when we want to draw relationships between three or more objects. The second way is a shortcut for when only two objects are involved. Let’s look at the first way as we create the Family relationship between Abraham, Mona, and their son Homer.

First, press the button labeled ‘Family’ (or some abbreviation of Family, depending on your font size) in the relationship toolbar to trigger the creation of a ‘Family’ relationship. Move the cursor over the Person object that is about to be in the first Parent role so that the connectable is highlighted (step 1 in Figure 4-6) and click the left mouse button. Then click again in the space between the two parents, to set the midpoint of the relationship. (step 2). Next click the second parent (step 3), and then the child (step 4). Finalize the creation of the relationship by clicking the right mouse button (alternatively, the relationship can be finalized by double-clicking the left mouse button when connecting the last object). The relationship between the chosen objects now appears in the Diagram Editor.

Let’s summarise that first way of creating a relationship. You click four times thus – first parent, empty space, second parent, child – and then right-click to finalize the relationship.

The second way can be used when we want to draw a relationship that only includes two objects. A good example here is a family without children; in our example, let’s connect Homer and Marge as if they were just married. Again, start the creation of a ‘Family’ relationship by pressing the ‘Family’ button in the relationship toolbar. Move the cursor over the first object for the relationship, Homer. Press and hold down the left mouse button, drag the cursor over the other object, Marge, and release the button. A binary relationship between the objects will now appear.

You can also add children to this relationship later. Take a look at the relationship you have just drawn. There is a small red dot in the middle of the line. Select the relationship by clicking that dot. One selection handle should now appear on top of the relationship dot. If you see such a handle also at either end of the relationship line, it means that you selected a role instead of the relationship – in this case, deselect the role (by holding down the Ctrl key while clicking the role) and select the relationship again.

Press the right mouse button and select Add a New Role... from the pop-up menu that opens. Move the cursor over the object you want to connect in the Child role (e.g. Lisa) and click the left mouse button. You can also click in empty space along the way to the object, to define the path the role will take. For example to add a ‘dogleg’ to Bart you would select the relationship, choose Add a New Role..., then click above Lisa, above Bart, and finally on Bart. You can also add breakpoints to the role line later by selecting the line, pressing the mouse button down at the point you want to add a breakpoint, and then dragging the newly created breakpoint to the desired position.

You can now continue to complete the Family Tree diagram by adding a role to Margaret so that it resembles the diagram in Figure 4-7. Remember to Commit your work!