Creating a Blank Constraint

You can create a blank constraint using the PAL Expression Editor. To do this, you can open the editor in one of three ways:

• Directly create a constraint at the PAL Constraints Tab 
• Create the constraint as an instance of :PAL-CONSTRAINT at the Instances Tab
• Attach a constraint to a class at the Classes Tab

The first two methods give identical results; they just reflect different ways of viewing constraints in Protégé. The third method actually attaches the constraint to the class. Attaching a constraint to a class creates an implicit range definition over all instances of the class, for all variables that appear in the constraint statement and that are not defined by an explicit range definition.

Note: You can also create constraints using the EZPAL plug-in, which provides template-based guidance to writing PAL constraints.  To access this plug-in, go to the Protégé Plug-In library, click on the Inference and Reasoning link, and then click on the EZPAL Tab Widget link.

At the Constraints Tab

To open the editor at the Constraints tab: 

1. Go to the PAL Constraints Tab
2. Click the Create button at the upper right of the Choose Constraints pane.
   A new constraint is created and the editor opens in a separate window.
   
   
   

At the Instances Tab

1. Go to the Instances Tab.
2. Display the classes under :SYSTEM-CLASS, display the classes under :CONSTRAINT, and click on :PAL-CONSTRAINT to highlight it. 
   
   
   
3. Go to the Direct Instances pane and click the Create button.
   A new constraint is created and the PAL Expression Editor appears in the Forms pane of the Instances tab.

At the Classes Tab

To create a constraint at the Classes Tab, and attach it to a class:

1. Go to the Classes Tab.
2. Highlight the class to which you wish to attach the constraint to be created.
   The Class Form for the selected class is displayed at the right of the Classes Tab.
3. Click the Create button at the upper right of the Class Constraints pane in the Class Form. 
   A new constraint is created and the PAL Expression Editor opens in s separate window.

Working With a New Constraint

Once the constraint has been created, you can:

• Name it by typing directly in the Name field
• Enter a description by typing directly in the Description field. 
• Define variable ranges by typing directly in the Range area, or using the Range Editor. 
• Create a statement by typing directly in the Statement area, or using the Statement Editor.

PAL Constraints User Interface/Creating a Blank Constraint

Next: Viewing a Constraint

PAL Table of Contents