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Week 12 [Fri, Oct 30th] - Topics

[W12.1] Sequence Diagrams: Basics

[W12.1a] Design → Modelling → Modelling Behaviors Sequence diagrams - basic :

[W12.2] Sequence Diagrams: Intermediate

[W12.2a] Design → Modelling → Modelling Behaviors Sequence diagrams - intermediate :
[W12.2b] Tools → UML → Sequence Diagrams → Parallel paths :
[W12.2c] Tools → UML → Sequence Diagrams → Reference frames :

Guidance for the item(s) below:

As with the class/object diagrams, let us refresh our memory of the sequence diagrams notations that you learned in TIC2002.

[W12.1] Sequence Diagrams: Basics

W12.1a :

Design → Modelling → Modelling Behaviors Sequence diagrams - basic

Video

Can draw basic sequence diagrams

Explain in your own words the interactions illustrated by this Sequence Diagram:

Consider the code below:

class Person {
    Tag tag;
    String name;

    Person(String personName, String tagName) {
        name = personName;
        tag = new Tag(tagName);
    }
}

class Tag {
    Tag(String value) {
        // ...
    }
}

class PersonList {
    void addPerson(Person p) {
        // ...
    }
}

Draw a sequence diagram to illustrate the object interactions that happen in the code snippet below:

PersonList personList = new PersonList();
while (hasRoom) {
    Person p = new Person("Adam", "friend");
    personList.addPerson(p);
}

Find notation mistakes in the sequence diagram below:

Follow up notes for the item(s) above:

Now that you know the basic notations for the sequence diagrams, here is a worked example of drawing sequence diagrams (basic notation) to match a code snippet.

Video Sequence diagrams (basic) - Item creation

Guidance for the item(s) below:

Earlier, you learned the basic syntax used in sequence diagrams. Now, let's learn some intermediate syntax.

[W12.2] Sequence Diagrams: Intermediate

W12.2a :

Design → Modelling → Modelling Behaviors Sequence diagrams - intermediate

Video

Can draw intermediate-level sequence diagrams

Method calls to static (i.e., class-level) methods are received by the class itself, not an instance of that class. You can use <<class>> to show that a participant is the class itself.

In this example, m calls the static method Person.getMaxAge() and also the setAge() method of a Person object p.

Here is the Person class, for reference:

What’s going on here?

a. Logic object is executing a parallel thread.
b. Logic object is executing a loop.
c. Logic object is creating another Logic instance.
d. One of Logic object’s methods is calling another of its methods.
e. Minefield object is calling a method of Logic.

(d)

Explain the interactions depicted in this sequence diagram.

First, the createParser() method of an existing ParserFactory object is called. Then, ...

Draw a sequence diagram to represent this code snippet.

if (isFirstPage) {
    new Quote().print();
}

The Quote class:

class Quote {

    String q;

    Quote() {
        q = generate();
    }

    String generate() {
        // ...
    }

    void print() {
        System.out.println(q);
    }

}

Show new Quote().print(); as two method calls.
As the created Quote object is not assigned to a variable, it can be considered as 'deleted' soon after its print() method is called.

W12.2b :

Tools → UML → Sequence Diagrams → Parallel paths

Can interpret sequence diagrams with parallel paths

UML uses par frames to indicate parallel paths.

Notation:

Logic is calling methods CloudServer#poll() and LocalServer#poll() in parallel.

If you show parallel paths in a sequence diagram, the corresponding Java implementation is likely to be multi-threaded because a normal Java program cannot do multiple things at the same time.

W12.2c :

Tools → UML → Sequence Diagrams → Reference frames

Can interpret sequence diagrams with reference frames

UML uses ref frame to allow a segment of the interaction to be omitted and shown as a separate sequence diagram. Reference frames help you to break complicated sequence diagrams into multiple parts or simply to omit details you are not interested in showing.

Notation:

The details of the get minefield appearance interactions have been omitted from the diagram.

Those details are shown in a separate sequence diagram given below.

Follow up notes for the item(s) above:

Here is a worked example of drawing sequence diagrams (intermediate notation) to match a code snippet.

Video Drawing sequence diagrams (intermediate) - TaskList#generateTask()

Video Drawing sequence diagrams (intermediate) - create Quote