Specification of Reactive Hardware/Software Systems - Electronic ...

11.4 Essential Specification Modelling 359
11.4.6 Modelling of Classes
The discussion in the previous subsection showed that there are many aspects of a
system that are incorporated simultaneously into the model by designing Message Flow
Diagrams. By focusing on instances, however, we have paid less attention to a number
of aspects related to classes. A model should preferably have:
a minimal number of classes;
classes that are designed for reuse;
well designed composites (generic and reusable);
well designed data structures (efficient access).
P:Product_Info_Keeper
Attributes:
Messages:
store
retrieve
servicePerformed
serviceOffered
D: PI
Attributes:
idNumber
Messages:
requires(Service)
markPending(Service)
markPerformed(Service)
D: Destination
Attributes:
name
address
zipcode
city
state
country
Messages:
P: Feeding_Unit_Image
Attributes:
Messages:
giveStatus
mounted
notMounted
feed
misFed
doubleFed
D: Service
Attributes:
type
name
Messages:
D: RequiredService
Attributes:
serviceState
Messages:
markUnserviced
markPending
markPerformed
provides
P: Transporter_Image
Attributes:
Messages:
wakeAt
encoderPuls
keeps
track of
D: Position
Attributes:
Messages:
setToZero
increment
+(PositionDelta)
-(Position)
=(Position)
asInitialPosition
D: InitialPosition
Attributes:
Messages:
P: Transporter
Attributes:
Messages:
move
models runs at
controls
Figure 11.16: Feeder Station: Object Class Diagram
D: Speed
Attributes:
Messages:
setToZero
setToMaximum
differ
D: PositionDelta
Attributes:
Messages:
Therefore the design of Object Class Diagrams (OCDs) should be performed simultaneously
with Message Flow Diagrams. OCDs give the opportunity to look at the system
has