Quick SysML Diagram Tutorial With Astah
- Parametric Diagram

Add a Parametric Diagram

Let’s draw the following parametric diagram. It is taken from “Figure D.24 – Defining Fuel Flow Constraints (Parametric Diagram)” of the SysML 1.5 specification.

1. Add a Parametric Diagram to the “PowerSubsystem” Block

If you are starting the tutorial from this page, download Astah SysML and the sample file.

1. Open the “PowerSubsystem Fuel Flow Definition” diagram.
2. Right-click the “PowerSubsystem” block and select [Add Parametric Diagram] from the pop-up menu. A parametric diagram opens.

Tip: To find a specific model quickly, use the [Search] pane.

A parametric diagram may look similar to the internal block diagram you drew earlier. In fact, a parametric diagram is a restricted internal block diagram, so you create it in the same way.

Constraint properties are created like parts in an internal block diagram, and constraint parameters like ports. However, the type of a constraint property must be a constraint block. Now let’s create a “fuelFlow: FuelFlow” constraint property.

Create a Constraint Property

A constraint property is typed by a constraint block and applies that block’s constraints in the diagram.

1. Create a “ParametricDomain” package from the pop-up menu of the project root in the Structure Tree.
2. Create a “FuelFlow” constraint block from the pop-up menu of the “ParametricDomain” package.
3. In the [Constraints] tab of the Property View, click [Add] and enter flowrate=press/(4*injectorDemand) in the constraint edit area.
4. Drag and drop the “FuelFlow” constraint block from the Structure Tree onto the parametric diagram, and rename it “fuelFlow”.

Add Value Properties

Let’s create the “ice.fi.fuelDemand” value property. First, modify the “PowerSubsystem Fuel Flow Definition” block definition diagram as shown below.

Or download the file that contains this block definition diagram (diagram name: “PowerSubsystem Fuel Flow Definition – after”).

1. Click the [Value Property] tool button on the tool palette.
   
2. Click on the diagram to open the [Add Property] dialog.
3. Expand the “ice: InternalCombustionEngine” part.
4. In the part hierarchy, select “fuelDemand: Real” in the “fi: FuelDemand” part and click [OK]. The “ice.fi.fuelDemand” value property appears on the diagram.
5. Repeat the steps and select “fuelFlowRate: Real” to create the second value property.

Constraint Parameter

1. Click the [Constraint Parameter] tool button, then click the “fuelFlow: FuelFlow” constraint property.
   
2. Rename the constraint parameter “injectorDemand”.
3. Add the constraint parameter “flowrate” in the same way.

Binding Connector

Now let’s connect the value properties and the constraint parameters with binding connectors.

1. Select [Binding Connector] on the tool palette.
2. Click the “ice.fi.fuelDemand” value property, then the “injectorDemand: Real” constraint parameter.
3. Connect the “ice.fi.fuelFlowRate” value property and the “flowrate: Real” constraint parameter in the same way.

You can download the file that contains this parametric diagram.