# Creating a Sub-model Space and Basic Sub-model Operations

In this section, you'll learn:

- How to create a Sub-model space

- How to open, close, select, move and resize a Sub-model space

- Constraints to moving and resizing a Sub-model space

Creating a Sub-model Space: As illustrated in Figure 9-7, creating a Sub-model space is easy, involving four simple steps.

Figure 9-7 Creating a Sub-model Space

Note: If you create Sub-models in the Mapping mode (as illustrated in Figure 9-7), you'll not get distracted by dialog details. It's possible to create Sub-model spaces when no flows are attached to the stock. However, you'll find it easier in the long haul if you think through the high-level stock and flow structure of your model, before you drill down to create Sub-models.

Opening, Closing, Selecting, Moving and Resizing: Figure 9-8 identifies the components of a Sub-model, and illustrates how to open, close, select, move, and resize a Sub-model space.

Figure 9-8 Opening, Closing, Selecting, Moving and Resizing a Sub-model Space

Constraints on Moving and Resizing a Sub-model Space: The software requires Sub-model spaces to be drawn below their icons. As a result, the software will enforce a minimum 40-pixel distance between the bottom of the Sub-model icon, and the top of its associated space. In addition, the software will not allow you to move either the left or right vertical border of the Sub-model space beyond the horizontal center of the Sub-model icon.

The positioning of a given Sub-model space will also be constrained by the position of other Sub-model spaces on the diagram. Specifically, while the software will allow Sub-model spaces to overlap one another, only one of the overlapping Sub-model spaces can be open at a time. When you open one overlapping sub-model space, all other overlapping sub-model spaces will be closed.