Information Technology Reference
In-Depth Information
Customer
Order
class name
name
address
1
0..*
date
status
attributes
association
calcTax
calcTotal
calcTotalWeight
1..*
1
operations
Payment
abstract class
amount
1
role name
generalization
multiplicity
line item
1..*
Credit
Cash
Check
OrderDetail
Item
number
type
extDate
cashTendered
name
bankID
quantity
taxStatus
shippingWeight
description
0..* 1
authorized
calcSubTotal
calcWeight
getPriceforQty
getWeight
authorized
Fig. 3.11
Class diagram (Miller
2003
)
which is associated with an
Item
class that describes the actual item being
ordered, and contains information regarding specific individual orders. From the
Payment
class, we find three derived classes,
Credit
,
Cash
, and
Check
, all of
which are, quite literally, different types of
Payment
(Fig.
3.11
).
3.4.2 Use Case Diagram
As we briefly explained earlier, a use case represents an interaction between a
software system and an external entity. A use case diagram then, similarly, models
the system from the view of an external observer. Like class diagrams, use case
diagrams are considered static views of a system. They are also a type of abstraction
in that they limit the information presented to that which is necessary and useful for
an external understanding of a system. In essence, while many aspects of software
development focus on the intricacies of how a software system works, a use case
diagrams describes a system based on what it does. A scenario describes what takes
place when some external entity interacts with the system. The entity that interacts
with the system in a scenario is an actor. A use case, then, is a compilation and
summary of all of the scenarios involved in an individual task. The figure below
illustrates a use case diagram for a patient's interactions with a medical clinic.
Figure
3.12
includes 4 use cases and 4 actors. Remember, each use case is
denoted by an oval, and each actor by a stick figure. Note that in this use case
diagram, each use case involves 2 separate actors. When all of the information is
