chapter 6 (object-oriented systems analysis and design using UML) Flashcards
1
Q
Object-Oriented Analysis and Design
A
- Works well in situations where complicated systems are
undergoing continuous maintenance, adaptation, and
design - Objects, classes are reusable
- The Unified Modeling Language (UML) is an industry
standard for modeling object-oriented systems
2
Q
Reusability
A
Recycling of program parts should reduce the costs of
development in computer-based systems
3
Q
Maintaining systems
A
Making a change in one object has a minimal impact
on other objects
4
Q
Object-Oriented Concepts
A
- Objects
- Classes
- Inheritance
5
Q
Objects
A
- Persons, places, or things that are relevant to the system
being analyzed - May be customers, items, orders, and so on
- May be GUI (graphical user interface) displays or text areas on a display
6
Q
Classes
A
- Defines the set of shared attributes and behaviors found
in each object in the class - Should have a name that differentiates it from all other
classes - Instantiate is when an object is created from a class
- An attribute describes some property that is possessed
by all objects of the class - A method is an action that can be requested from any
object of the class
7
Q
Inheritance
A
- When a derived class inherits all the attributes and
behaviors of the base class - Reduces programming labor by using common objects
easily - A feature only found in object-oriented systems
8
Q
CRC Cards and Object Think
A
- CRC
– Class
– Responsibilities
– Collaborators - CRC cards are used to represent the responsibilities of
classes and the interaction between the classes
9
Q
Interacting during a CRC Session
A
- Identify all the classes you can
- Create scenarios
- Identify and refine responsibilities
10
Q
The Unified Modeling Language (UML)
Concepts and Diagrams
A
- Things
- Relationships
- Diagrams
11
Q
Things
A
- Structural things are:
– Classes, interfaces, use cases, and other elements that provide
a way to create models
– They allow the user to describe relationships - Behavioral things
- Describe how things work
– Interactions and state machines - Group things
– Used to define boundaries - Annotational things
– Can add notes to the diagrams
12
Q
Relationships
A
- Structural relationships
– Tie things together in structural diagrams - Behavioral relationships
– Used in behavioral diagrams
13
Q
Structural Relationships
A
- Dependencies
- Aggregations
- Associations
- Generalizations
14
Q
Behavioral Relationships
A
- Communicates
- Includes
- Extends
- Generalizes
15
Q
Structural diagrams
A
Used to describe the relation between classes
16
Q
Behavioral diagrams
A
Used to describe the interaction between people
(actors) and a use case (how the actors use the system)
17
Q
Structural Diagrams
A
- Class diagrams
- Object diagrams
- Component diagrams
- Deployment diagrams
18
Q
Behavioral Diagrams
A
- Use case diagrams
- Sequence diagrams
- Collaboration diagrams
- Statechart diagrams
- Activity diagrams
19
Q
Commonly Used UML Diagrams
Use case diagram
A
– Describing how the system is used
– The starting point for UML modeling
20
Q
Use case scenario
A
A verbal articulation of exceptions to the main
behavior described by the primary use case
21
Q
Activity diagram
A
Illustrates the overall flow of activities
22
Q
Sequence diagrams
A
Show the sequence of activities and class relationships
23
Q
Class diagrams
A
Show classes and relationships
24
Q
Statechart diagrams
A
Show the state transitions
25
Use Case Modeling
* Describes what the system does, without describing how
the system does it
* Based on the interactions and relationships of individual
use cases
* Use case describes
– Actor
– Event
– Use case
26
Activity Diagrams
* Show the sequence of activities in a process, including
sequential and parallel activities, and decisions that are made
* Symbols
– Rectangle with rounded ends
– Arrow
– Diamond
– Long, flat rectangle
– Filled-in circle
– Black circle surrounded by a white circle
– Swimlanes
27
Creating Activity Diagrams
* Created by asking what happens first, what happens
second, and so on
* Must determine what activities are done in sequence or in
parallel
* The sequence of activities can be determined from
physical data flow diagrams
* Can be created by examining all the scenarios for a use
case
28
Swimlanes
* Useful to show how the data must be transmitted or
converted
* Help to divide up the tasks in a team
* Makes the activity diagram one that people want to use to
communicate with others
29
Activity Diagrams and Test Plans
* Activity diagrams may be used to construct test plans
* Each event must be tested to see if the system goes to
the next state
* Each decision must be tested
30
Use an activity diagram when:
– It helps to understand the activities of a use case
– The flow of control is complex
– There is a need to model workflow
– When all scenarios for a use case need to be shown
31
Sequence Diagrams
* Illustrate a succession of interactions between classes or
object instances over time
* Often used to show the processing described in use case
scenarios
* Used to show the overall pattern of the activities or
interactions in a use case
32
Communication Diagrams
* Describes the interactions of two or more things in the
system that perform a behavior that is more than any
one of the things can do alone
* Shows the same information as a sequence diagram,
but may be more difficult to read
* Emphasizes the organization of objects
* Made up of objects, communication links, and the
messages that can be passed along those links
33
Class Diagrams
* Show the static features of the system and do not
represent any particular processing
* Show the nature of the relationships between classes
* Show data storage requirements as well as processing
requirements
* Classes
* Attributes
– Private
– Public
– Protected
* Methods
– Standard
– Custom
34
Method Overloading
* Including the same method (or operation) several times in
a class
* The same method may be defined more than once in a
given class, as long as the parameters sent as part of the
message are different
35
Types of Classes
* Entity classes
* Interface classes
* Abstract classes
* Control classes
36
Entity Classes
* Represent real-world items
* The entities represented on an entity-relationship
diagram
37
Interface or Boundary Classes
* Provide a means for users to work with the system
* Human interfaces may be a display, window, Web form,
dialogue box, touch-tone telephone, or other way for
users to interact with the system
* System interfaces involve sending data to or receiving
data from others
38
Abstract Classes
* Linked to concrete classes in a
generalization/specialization relationship
* Cannot be directly instantiated
39
Control Classes
* Used to control the flow of activities
* Many small control classes can be used to achieve
classes that are reusable
40
Sequence diagrams may be discussed using three
layers:
– Presentation layer, what the user sees, corresponding
to the interface or boundary classes
– Business layer, containing the unique rules for this
application, corresponding roughly to control classes
– Persistence or data access layer, for obtaining and
storing data, corresponding to the entity classes
41
Defining Messages and Methods
* Each message may be defined using a notation similar to
that described for the data dictionary
* The methods may have logic defined using structured
English, a decision table, or a decision tree
42
Create Sequence Diagrams
* Include the actor from the use case diagram
* Define one or more interface classes for each actor
* Each use case should have one control class
* Examine the use case to see what entity classes are
required
* The sequence diagram may be modified when doing
detailed design
43
Creating a Test Plan from a Sequence Diagram
* Does each method return correct results?
* Ensure that entity classes store or obtain the correct
attribute values
* Verify that all JavaScript paths work correctly
* Ensure that the server control classes work correctly
* Ask, “What may fail?”
* Determine what to do if something can fail
44
The connections between classes
– Associations
– Whole/part
45
Associations
* The simplest type of relationship
* Association classes are those that are used to break up a
many-to-many association between classes
* An object in a class may have a relationship to other
objects in the same class, called a reflexive association
46
Whole/Part Relationships
* When one class represents the whole object, and other
classes represent parts
* Categories
– Aggregation
– Collection
– Composition
47
Aggregation
* A “has a” relationship
* Provides a means of showing that the whole object is
composed of the sum of its parts
48
Collection
* Consists of a whole and its members
* Members may change, but the whole retains its identity
* A weak association
49
Composition
* The whole has a responsibility for the parts, and is a
stronger relationship
* If the whole is deleted, all parts are deleted
50
Generalization/Specialization Diagrams
* Generalization
* Inheritance
* Polymorphism
* Abstract classes
* Messages
51
Generalization
* Describes a relationship between a general kind of thing
and a more specific kind of thing
* Described as an “is a” relationship
* Used for modeling class inheritance and specialization
* General class is a parent, base, or superclass
* Specialized class is a child, derived, or subclass
52
Inheritance
* Helps to foster reuse
* Helps to maintain existing program code
53
Polymorphism
* The capability of an object-oriented program to have
several versions of the same method with the same
name within a superclass/subclass relationship
* The subclass method overrides the superclass method
* When attributes or methods are defined more than once,
the most specific one is used
54
Abstract Classes
* Abstract classes are general classes
* No direct objects or class instances, and is only used in
conjunction with specialized classes
* Usually have attributes and may have a few methods
55
Finding Classes
* During interviewing or JAD sessions
* During facilitated team sessions
* During brainstorming sessions
* Analyzing documents and memos
* Examining use cases, looking for nouns
56
Determining Class Methods
* Standard methods
* Examine a CRUD matrix
57
Messages
* Used to send information by an object in one class to an
object in another class
* Acts as a command, telling the receiving class to do
something
* Consists of the name of the method in the receiving
class, as well as the attributes that are passed with the
method name
* May be thought of as an output or an input
58
Statechart Diagrams
* Used to examine the different states that an object may have
* Created for a single class
– Objects are created, go through changes, and are deleted
or removed
* Objects
* States
* Events
– Signals or asynchronous messages
– Synchronous
– Temporal events
59
statechart diagrams created when:
– A class has a complex life cycle
– An instance of a class may update its attributes in a
number of ways through the life cycle
– A class has an operational life cycle
– Two classes depend on each other
– The object’s current behavior depends on what
happened previously
60
Packages
* Containers for other UML things
* Show system partitioning
* Can be component packages
* Can be physical subsystems
* Use a folder symbol
* May have relationships
61
The steps used in UML are:
– Define the use case model
– Continue UML diagramming to model the system
during the systems analysis phase
– Develop the class diagrams
– Draw statechart diagrams
– Begin systems design by refining the UML diagrams
– Document your system design in detail
