Create Activity Diagram Programmatically

Since R2026a

This example shows how to create an activity diagram programmatically. An activity diagram describes system behavior that models the flow of tokens from inputs to outputs through a controlled sequence of actions. You can use activity diagrams to conceptualize a system, visualize functional flow through actions or decisions, and understand how system components interact with one another. To learn more about authoring activity diagram, see, Author a Simple Activity Diagram.

In this example, you create an activity diagram to illustrate the steps involved in placing an order, checking inventory availability, and canceling the order if items are unavailable.

Create New Activity Diagram

Create a new activity diagram named AuthorActivity using the systemcomposer.createActivity function.

activityName = 'AuthorActivity';
adModel = systemcomposer.createActivity(activityName,true);
activity = adModel.Activity;

Add Initial Node and Action Nodes

Add an initial node and required action nodes using the addNode function.

init1 = addNode(activity,'init1','initial');
action1 = addNode(activity,'Place Order','action');   
action2 = addNode(activity,'Authorize Payment','action');  
action3 = addNode(activity,'Check Inventory','action');  
action4 = addNode(activity,'Cancel Order','action');  
action5 = addNode(activity,'Fulfill Order','action'); 

Define Action Node Behavior and Add Pins

Add the behavior type of an action node using the setBehaviorType function. You can specify the MATLAB® functions for an action node with a behavior type of MATLAB by using the BehaviorDefinition property.

setBehaviorType(action1,'MATLAB');
action1.BehaviorDefinition = 'PlaceOrder';
setBehaviorType(action2,'Activity');
setBehaviorType(action3,'MATLAB');
action3.BehaviorDefinition = 'CheckInventory';

You can add pins on an action node using the addNode function. For more information on pins, see Pin.

outPin1 = addPin(action1,'order','out');
inPin1 = addPin(action2,'order1','in');
outPin2 = addPin(action2,'order2','out');
inPin2 = addPin(action3,'order3','in');
outPin3 = addPin(action3,'order4','out');
inPin1.IsStreaming = true;
outPin2.IsStreaming = true;

Create Nested Activity

You can create a nested activity for an action node with Activity behavior type.

childActivity = action2.ChildActivity;
childAction1 = addNode(childActivity,'Enter Card Details','action');
childAction2 = addNode(childActivity,'Authenticate Details','action');

Add Control Nodes

Add a join or fork node and a merge or decision node. For more information on control nodes, see systemcomposer.activity.ControlNode.

jfork = addNode(activity,"jfork","joinfork"); 
decMerge1 = addNode(activity,"decMerge1","mergedecision");
decMerge2 = addNode(activity,"decMerge2","mergedecision");

Add Flow Final and Activity Final Nodes

Add a flow final node and an activity final node.

ffinal = addNode(activity,"ffinal","flowfinal");
afinal = addNode(activity,"afinal","activityfinal");

Connect Flows

Connect the flows to complete the activity diagram. You can create guard expressions for flows that output from decision node.

flow1 = connect(init1,action1);
flow2 = connect(outPin1,jfork);
flow3 = connect(jfork,inPin1);
flow4 = connect(jfork,inPin2);
flow5 = connect(outPin2,decMerge1);
flow6 = connect(outPin3,decMerge2);
flow7 = connect(decMerge2,action5);
flow8 = connect(decMerge2,action4);
flow9 = connect(decMerge1,action5);
flow10 = connect(decMerge1,action4);
flow11 = connect(action4,ffinal);
flow12 = connect(action5,afinal);

Create guard expression for flows that output from decision node.

flow7.Guard = 'token == 1';
flow8.Guard = 'token == 0';

You can use the Simulink.BlockDiagram.arrangeSystem function to improve the layout of the activity diagram model.

Simulink.BlockDiagram.arrangeSystem('AuthorActivity');