Midterm Study - UML Class

Question 1

How do you find system requirements needed for “things”?

Answer 1

WHAT THINGS DOES THE SYSTEM NEED TO KNOW ABOUT AND STORE INFORMATION ABOUT?

Question 2

What are some different types of things?

Answer 2

Question 3

What is the procedure for developing an initial list of things?

Answer 3

Step1: Using the event table and information about each event, identify all nouns in the system.

Step2: Using other information from existing systems, current procedures, and current reports or forms, add items or categories of information needed.

Step3: Refine list and record assumptions or issues to explore.

Question 4

What is an object?

Answer 4

An object is an entity(thing) that has a well-defined role in the application domain, and has a state, behaviour and identity.

Question 5

Explain the parts in an object?

Answer 5

Class: Type of thing

Object: each specific thing

Methods: Behaviours of objects of the class

State: the values for the attributes (which can be set and changed by methods)

Question 6

What are the 3 main parts to a class in a class diagram?

Answer 6

Class name at the top, List of attributes in the middle, and list of operations or methods on the bottom.

Question 7

What is a class diagram?

Answer 7

The class diagram models classes of objects instead of data entities.

Include Generalization/Specialization & Aggregation

Question 8

What is Generalization/Specialization Hierarchies?

Answer 8

General superclasses to specialized subclasses.

Inheritance allows subclasses to share characteristics of their superclasses.

Question 9

What is aggregation (whole-part hierarchies)?

Answer 9

Aggregation relates objects and its parts, defines objects in terms of its parts.

Example: A Personal Computer is an object in itself, but is composed of a CPU, Monitor, Keyboard etc… It is made of of other objects that can exist on their own, therefore it represents aggregation

Question 10

What is Composition (whole-part hierarchies)?

Answer 10

Similar to aggregation where the one object is made up of many objects except the objects belong to the whole object.

Example, the room is “part of” a building, but if the building is gone so is the room.

Question 11

How do you represent a class that has a many-to-many relationship between two other classes?

Answer 11

With a dotted line.

Question 12

What are the three types of operations in an object model? (class)

Answer 12

Query (getter): An operation that accesses the state of an object but does not alter the state.

Update (setter): An operation that alters the state of an object.

Constructor: An operation that creates a new instance of a class.

Question 13

How do you represent associations?

Answer 13

Association

• A relationship between object classes
• Degree may be unary, binary, ternary or higher
• Depicted as a solid line between participating classes

Association Role

• The end of an association where it connects to a class
• Each role has multiplicity, which indicates how many objects participate in a given association relations

Question 14

What does a Unary association relationship look like?

Answer 14

Question 15

What does a binary association relationship look like?

Answer 15

Question 16

What does a ternary association relationship look like?

Answer 16

Question 17

What is an overlapping constraint and what would it look like in a diagram?

Answer 17

Overlapping: A descendant may be descended from more than one of the subclasses.

Question 18

What would a diagram look like that shows abstract operations, class scope attributes and polymorphism?

Answer 18

Question 19

How would a detailed class in a class diagram look?

Answer 19

Question 20

What are constraints and what do they look like in a diagram?

Answer 20

Question 21

What does an abstract class look like in a diagram?

Answer 21

Question 22

How would you display an interface in a diagram?

Answer 22

Question 23

What are the standard stereotypes found in design models?

Answer 23

Question 24

What is coupling?

Answer 24

Coupling is a general term derived from navigation visibility, a qualitative measure of how closely classes in a design class diagram are linked. Based on a number of navigation arrows on design class diagrams. Low: system is easier to understand and maintain (preferred). With coupling, a change in one class ripples throuhout the entire system.

Question 25

What types of coupling are there and list them from bad to good?

Answer 25

Content (bad)

Common

Contol

Stamp

Data (good)

Question 26

What is data coupling (good)?

Answer 26

Data coupling - Data coupling is when modules share data through, for example, parameters. Each datum is an elementary piece, and these are the only data which are shared (e.g. passing an integer to a function which computes a square root)

Question 27

What is stamp coupling?

Answer 27

Stamp coupling (Data-structured coupling) - Stamp coupling is when modules share a composite data structure, each module not knowing which part of the data structure will be used by the other (e.g. passing a student record to a function which calculates the student’s GPA

Question 28

What is control coupling?

Answer 28

Control coupling - Control coupling is one module controlling the logic of another, by passing it information on what to do (e.g. passing a what-to-do flag)

Question 29

What is external coupling?

Answer 29

External coupling - External coupling occurs when two modules share an externally imposed data format, communication protocol, or device interface.

Question 30

What is common coupling?

Answer 30

Common coupling - Common coupling is when two modules share the same global data (e.g. a global variable).

Question 31

What is content coupling?

Answer 31

Content coupling - Content coupling is when one module modifies or relies on the internal workings of another module (e.g. accessing local data of another module)

Question 32

What is cohesion?

Answer 32

Cohesion is a qualitative measure of consistency of functions (methods) within a single class.

High cohesive example: Student class methods to enter student ID and name

Low cohesive example: Student class also has methods to make classroom assignments or assign professors to courses

Separation of responsibility – divide low cohesive class into several highly cohesive classes. High cohesion is desired. Classes with low cohesion are Hard to maintain, hard to reuse, difficult to understand

Question 33

What types of cohesion are there and list them from bad to good.

Answer 33

Coincidental (bad)

Logical

Temporal

Procedural

Communicational

Informational

Functional (good)

Question 34

What is Functional cohesion?

Answer 34

Functional cohesion is when parts of a module are grouped because they all contribute to a single well-defined task of the module (a perfect module).

Question 35

What is informational (sequential) cohesion?

Answer 35

Informational (sequential) cohesion is when parts of a module are grouped because the output from one part is the input to another part (e.g. a function which reads data from a file and processes the data)

Question 36

What is communicational cohesion?

Answer 36

Communicational cohesion is when parts of a module are grouped because they operate on the same data (e.g. a method updateStudentRecord which operates on a student record, but the actions in which the method performs are not clear)

Question 37

What is procedural cohesion?

Answer 37

Procedural cohesion is when parts of a module are grouped because they always follow a certain sequence of execution (e.g. a function which checks file permissions and then opens the file)

Question 38

What is temporal cohesion?

Answer 38

Temporal cohesion is when parts of a module are grouped by when they are processed - the parts are processed at a particular time in program execution (e.g. a function which is called after catching an exception which closes open files, creates an error log, and notifies the user)

Question 39

What is logical cohesion?

Answer 39

Logical cohesion is when parts of a module are grouped because of a slight relation (e.g. using control coupling to decide which part of a module to use, such as how to operate on a bank account)

Question 40

What is coincidental cohesion?

Answer 40

Coincidental cohesion is when parts of a module are grouped arbitrarily; the parts have no significant relationship (e.g. a module of frequently used functions).