Lecture 2-UML

Question 1

What does a use case describe?

Answer 1

It describes sequences of actions a system performs that yield an observable result of value to a particular actor.

Question 2

What are 3 features of use cases?

Answer 2

-They capture functional requirements
-They are derived from the Vision Document
-They collect a number of(+) scenarios(normal and abnormal)

Question 3

What are the 3 categories of UML diagrams?

Answer 3

1.Structural –>element of spec. irrespective of time :
-class
-component
-deployment
-object
-package
2. Behavioral
-activity
-state machine
-use case
3.Interaction–>emphasize object interaction:
-communication(collaboration)
-sequence
-Interaction overview
-Timing

Question 4

What are the 3 applications of use case diagrams?

Answer 4

1.Determining requirements
2.Communicating with clients
3.Generating test cases

Question 5

Why do we use class diagrams?

Answer 5

Gives an overview of a system by showing its classes and the relationships among them. –>They display what interacts but not what happens when they do interact

Question 6

What are 3 characteristics of class diagrams?

Answer 6

-They are static
-They show attributes and operations of each class
-Good way to describe the overall architecture of system components.

Question 7

What are the 5 characteristics of classes?

Answer 7

-A class represents a concept
-Encapsulates state –> attributes & behaviour–> operations
-Each attribute has a type
-Each operation has a signature
-Class name is the ONLY MANDATORY info

Question 8

What are the 3 characteristics of instances?

Answer 8

-It represents a phenomenon
-Name of an instance is UNDERLINED & can contain the class of the instance
-Attributes represented with their values

Question 9

What is the UML class notation?

Answer 9

A class is a rectangle divided intro 3 parts:
-class name
-class attributes
-Class operations
*IF ABSTRACT: IN ITALIC

Question 10

What are the type of modifiers(4)?

Answer 10

-Private : -
-Public : +
-Protected : #
-Static : underlined

Question 11

What are the 4 class relationships?

Answer 11

-Association(unary, binary)
-Aggregation(collection-member relationship)
-Composition(strong lifecycle dependency)
-Inheritance

Question 12

What is an aggregation relationship?

Answer 12

-It’s an association with a collection-member relationship
-Hollow diamond on the collection side
-No sole ownership implied

Question 13

What is a composition relationship?

Answer 13

-“If the engine is destroyed, so is the car”
-Filled diamond shaped arrowhead

Question 14

What is the inheritance relationship?

Answer 14

-Superclass: has common attributes methods for all subclasses
-Subclasses : inherit the attributes and methods of the superclass
-Empty arrowhead

Question 15

What are the 4 UML multiplicities ?

Answer 15

• 0..1 : zero or one instance
• 0..* or * : no limit
  -1: exactly one instance
• 1..*: at least one instance

Question 16

What is a System Sequence Diagram(SSD)?

Answer 16

It shows the external actors that interact directly within the system, the system itself(black box), and the system events that the actors generate.

*Time proceeds downward
*Ordering of events should follow their order in the scenario

Question 17

Why draw a system sequence diagram?

Answer 17

Because a software system reacts to 3 things:
1) external events from actors
2)timer events
3)faults or exceptions (often from external sources)

Question 18

What does : imply in SSD?

Answer 18

An instance

Question 19

When are SSDs usually created in UP?

Answer 19

In the elaboration phase

Question 20

When to use SSD(2)?

Answer 20

-Drawn for 1 particular scenario
-To show the bahvior of several actors within a single use case

Question 21

What is an activity diagram and what does it do(2) ?

Answer 21

-They show sequential and parallel activities in a process
-They visualize the flow of events in a use case

Question 22

What does an activity diagram focus on vs not focus on?

Answer 22

-It shows the tasks that need to be done with what inputs and in what order.
-It does not show who is doing the task, unless we use swim lanes.

Question 23

Where are activity diagrams usually applicable in UP?

Answer 23

Within the Business Modelling discipline

Question 24

When to use activity diagrams(2)?

Answer 24

-They can be used for both control flow and data flow modelling.
-In complex use cases with many alternative flows

Question 25

What is a UML state machine diagram and what does it do?

Answer 25

-It illustrates the interesting events and states of an object, and the behaviour of an object in reaction to an event.
-Used for complex page flows

Question 26

When to use State Machine diagrams?

Answer 26

When we have state-dependent classes and state-dependent objects.

Question 27

What is special about state machine in the UP?

Answer 27

-There is not one model in the UP called “state model”–> any element in any model (design model, business object model, …) may have a state machine.