Week 6

Question 0

What is a data flow diagram (DFD)?

Answer 0

A data flow diagram represents both physical and logical information systems. It is useful for depicting purely logical information flows.

Question 1

Draw the three-tier architecture

Answer 1

See slide number six of week six

Question 2

List and describe the four symbols of a data flow diagram (DFD)

Answer 2

1. Process: work or actions performed on data (inside the system)
2. Data store: data at rest (inside the system)
3. Source/sink: external entity that represents the origin or destination of data (outside the system)
4. Data flow: arrows depicting the movement of data.

Question 3

Describe balancing and it’s effect on DFD’s

Answer 3

Balancing is the conservation of inputs and outputs to a data flow diagram process when the process is decomposed to a lower level. For example, a DFD is unbalanced when the context diagram and the level-0 diagram do not have the same number of inputs(sources)/outputs(sinks).

Question 4

Describe the use case diagram

Answer 4

Use case diagram is a picture showing system behavior along with the key actors that interact with the system. The use case diagram is considered to be abstract when it is initiated by another use case.

Question 5

Describe the symbols of a use case diagram

Answer 5

1. Actor: the actor is a role, not an individual. It is involved with the functioning of the system at some basic level.
2. Use case: the use case represents a single system function.
3. System boundary: the system boundary includes all of the relevant use cases. It is the dividing line between the system and its environment.
4. Connection: a connection is an association between actor do you settings. It depicts a usage relationship. there are special connections which are called extends and includes.

Question 6

What are the limitations of DFD’s?

Answer 6

Timing is not represented well on DFD
Iterative development is used. Analysts must redraw the diagram several times before reaching the closest approximation to the system being models.

Question 7

What are the three benefits of object oriented design (OO)

Answer 7

1. Reduced complexity
2. Reuse
3. Revise

Question 8

Object-oriented analysis and design: What is an object?

Answer 8

Has a well-defined role in the application domain, as well as a state, behavior, and identity characteristics.

Question 9

Object-oriented analysis and design: What is a class?

Answer 9

A logical grouping of objects that have the same or similar attributes, relationships, and behaviors.

Question 10

What are the major principles of Object-oriented analysis and design?

Answer 10

1. Encapsulation: hiding the internal implementation details of an object from its external view. In other words making it private.
2. Inheritance: The ability for a class to extend or override functionality of another class. These so-called subclass has a whole section that is derived (inherited) from the superclass.
3. Polymorphism: The same method (operation) may apply to two or more classes in different ways