systemcomposer.interaction.SeqFragment

Weak sequencing fragment in interaction

Since R2024a

Description

A SeqFragment object is a container for operands in a sequence diagram that specifies the behavior of contained elements.

A Seq Fragment represents that the messages in its operand are weakly sequenced. Weak sequencing is also the default interpretation of messages on an interaction, and so this fragment is often not explicitly required.

Weak sequencing means that the order of message events on a lifeline must be followed, but there is no ordering constraint between message events on different lifelines, except that for a given message, the send event occurs before the receive event.

A weak sequencing fragment is drawn as a box in the sequence diagram, with the label Seq in the box header. The operand is then drawn within this box as a separate section.

Creation

Access Fragment objects via the RootFragment property of the corresponding systemcomposer.interaction.Interaction object. Access the Operand property of the root fragment and then, if there are fragments within the root operand, access the Fragment property of the root operand and iterate over it to view details about each of the fragments.

Properties

Operands — Operands

array of operand objects

Operands, specified as an array of systemcomposer.interaction.Operand objects.

CoveredLifelines — Lifelines covered

array of lifeline objects

Lifelines covered, specified as an array of systemcomposer.interaction.Lifeline objects.

Parent — Parent operand

operand object

Parent operand, specified as an systemcomposer.interaction.Operand object.

UUID — Universal unique identifier

character vector

Universal unique identifier, specified as a character vector.

Example: '91d5de2c-b14c-4c76-a5d6-5dd0037c52df'

Data Types: char

Examples

Inspect Sequence Diagrams with Programmatic Interfaces

This example shows how to use read-only API workflows to navigate sequence diagrams in System Composer™ and display information about each of the elements.

Open Traffic Light Example

Open the traffic light example architecture model so that you can inspect the sequence diagrams visually and confirm the programmatic outputs.

model = systemcomposer.openModel("TLExample");

On the System Composer toolstrip, navigate to Modeling > Sequence Diagram to view the sequence diagrams associated with the model.

Programmatically Navigate Sequence Diagram

Collect the sequence diagrams represented by interactions that contain specific interactions of elements in the model.

interactions = model.getInteractions;

For the first interaction, extract the name of the sequence diagram.

disp("The first sequence diagram is called " + interactions(1).Name + ".")

The first sequence diagram is called SignalSequence.

For this sequence diagram, display each lifeline and the component the lifeline represents.

for i = 1:length(interactions(1).Lifelines)
    disp("The " + interactions(1).Lifelines(i).Name + ...
    " lifeline represents the " + ...
    interactions(1).Lifelines(i).RelatedElements.Name + ...
    " component.")
end

The ped lamp lifeline represents the ped lamp component.
The lampController lifeline represents the lampController component.
The poller lifeline represents the poller component.
The source lifeline represents the source component.

Now, display the contents of one message in the root fragment.

disp("The sequence diagram message starting at the " + ...
    interactions(1).RootFragment.Operands.Fragments(1).Name + ...
    " message end is of type " + ...
    string(interactions(1).RootFragment.Operands.Fragments(1).Message.Type) + ...
    " and the message label is " + ...
    interactions(1).RootFragment.Operands.Fragments(1).Message.Condition + ".")

The sequence diagram message starting at the switchout message end is of type Signal and the message label is rising(sw-1).

Use Iterator Utility to Step Through Sequence Diagram

Step through the Inhibit sequence diagram using the Iterator utility.

interaction = model.getInteraction('Inhibit');
interaction.open

Display the annotation from the interaction.

disp(interaction.Annotations.Content)

When inhibit is true, it means pedestrian crossing is not controlled by a walk signal on this intersection.

Use an iterator to navigate through all elements of a sequence diagram before extracting their properties.

iterator = systemcomposer.interaction.Iterator(interaction.RootFragment);
next = iterator.next;
while ~isempty(next)
    disp(class(next))
    next = iterator.next;
end

systemcomposer.interaction.RootFragment
systemcomposer.interaction.Operand
systemcomposer.interaction.MessageEvent
systemcomposer.interaction.MessageEvent
systemcomposer.interaction.MessageEvent
systemcomposer.interaction.MessageEvent
systemcomposer.interaction.AltFragment
systemcomposer.interaction.Operand
systemcomposer.interaction.MessageEvent
systemcomposer.interaction.MessageEvent
systemcomposer.interaction.MessageEvent
systemcomposer.interaction.MessageEvent
systemcomposer.interaction.Operand
systemcomposer.interaction.MessageEvent
systemcomposer.interaction.MessageEvent

More About

Definitions

Term	Definition	Application	More Information
sequence diagram	A sequence diagram represents the expected interaction between structural elements of an architecture as a sequence of message exchanges.	Use sequence diagrams to describe how the parts of a system interact.	Describe System Behavior Using Sequence Diagrams
lifeline	A lifeline is represented by a head and a timeline that proceeds down a vertical dotted line.	The head of a lifeline represents a component in an architecture model.	Add Lifelines and Messages
message	A message sends information from one lifeline to another. Messages are specified with a message label.	A message label has a trigger and a constraint. A trigger determines whether the message occurs. A constraint determines whether the message is valid.	Create Messages in Sequence Diagram
gate	A gate in a sequence diagram represents the root architecture of the corresponding architecture model.	Connect messages to gates to represent architecture ports.	Create Sequence Diagram Gates
annotation	An annotation describes the elements of a sequence diagram.	Use annotations to provide detailed explanations of elements or workflows captured by sequence diagrams.	Use Annotations to Describe Elements of Sequence Diagram
fragment	A fragment indicates how a group of messages specified within execute or interact.	A fragment is used to model complex sequences, such as alternatives, in a sequence diagram.	Author Sequence Diagram Fragments
operand	An operand is a region in a fragment. Fragments have one or more operands depending on the kind of fragment. Operands can contain messages and additional fragments.	Each operand can include a constraint to specify whether the messages inside the operand execute. You can express the precondition of an operand as a MATLAB® Boolean expression using the input signal of a lifeline.	Add Fragments and Operands

Version History

Introduced in R2024a