Diagram Elements

Objects – Controllers and Controlled Processes

Controllers and Controlled Processes are HCS modelling elements. They are visualized as rectangles with a label representing the name of the controller or controlled process respectively. The icon in the upper left corner indicates the type of element.

   Icon shown for Controllers

  Icon shown for Controlled Process

How To: Create Controller (analogously for Controlled Processes)

1. Left click to grab and the Controller element, then drag and drop from the Toolbox onto the Canvas. Release the Controller where you want it to appear on the canvas, but you can reposition and resize at any time.
2. By default, the controller is named “New Controller” and after setting the element in place on the canvas the name is immediately selected for editing. Simply rename the element by typing the new name.
   

   
   How To: Rename Controller (analogously for Controlled Processes)

Throughout the modeling and diagramming process, there are multiple ways to rename a controller set on the canvas:

• Select the Controller on the Canvas and hit F2
• Select the Controller on the canvas, display the context menu by right-clicking with the mouse and select “Rename”.
  
• Select the Controller on the Canvas and rename it via the Properties panel
• In the properties panel you may optionally capture a description for the controller after renamnig.

How To: Delete a Controller (analogously for Controlled Processes)

With respect to the deletion of controllers the STPA Module differentiates between:

• Delete from Diagram: The controller is deleted from the diagram but not from the model
• Delete from Model: The controller is deleted from the diagram but not from the model. This option is not available when the controller appears on other diagrams

Reminder: the “Del” key deletes the controller from the diagram only.

How To: Convert Controller to Controlled Process and vice versa

A controller may be converted into a controlled process and vice versa via the Properties panel.

Note that converting a controller into a controlled process is disabled if the controller issues control actions, because this goes against the STPA HCS modelling rules, where a controlled process can’t issue control actions

How To: Cut Copy Paste Controllers (analogously for Controlled Processes)

During the modeling and diagramming process, copying and pasting elements and connectors can save a lot of time.

1. Select the controller on the canvas with a left mouse click,
2. Display the context menu with right mouse click
3. Select the copy or paste, depending upon the desired action, with left mouse click.

Actions – Control Actions and Feedback

How to: Create Control Actions and Feedback

1. To create a new element on the canvas, such as a controller, select the desired object from the Toolbox to drag and drop on the canvas. Alternatively, the Canvas Context Menu (right mouse click on the canvas) can also be used to achieve the same effect.
2. Additionally, existing controllers and/or controlled processes that were defined in the ‘Diagram Elements” of the HCS model, or in other HCS diagrams, can be created in the canvas via the Context Menu.
3. After elements are created, their displaying text can easily be edited by double clicking on them. They can also be edited via the Property Grid on the right-hand of the canvas after selecting the specified element.

Annotation Layer

The Annotation Layer is very useful when diagramming and can be used within the canvas through various elements.

Annotation Elements are aesthetic elements that can be used on the Diagrams for more descriptive purposes. They hold no data on their own and do not affect the Model in any way.

Annotations can be enabled and disabled with a single click by using the button on the Toolbar on top of the canvas.