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

12.3 The Essential Specification 387
Service_
Scheduler
Feeder_Station
Feeder_Controller
Product_
Product_
pipo
Product_
i Input_
pihp
Info_
Output_
o
Handler
Keeper
Handler
piti
wake
Transporter_
Image
Transporter
pihs
wake
prks
Feeding_Unit_
fuis fesa
Image
titr fufu
poti
Feeding_
Unit
poss
pisa
Service_
Administrator
DISTR
Figure 12.8: Instance Structure Diagram of Feeder Station
of the mailing machine, the diagram shows a number of related process classes. For
each class zero or more attributes and messages are specified. Some relations between
classes are also indicated.
The diagram of Figure 12.9 shows that process class Product Info Keeper is related to data
class PI through an aggregation relation 11 . Each Product Info Keeper contains zero or
one 12 PI objects. A PI object, on its turn, is built from zero or one Destination objects and
zero or more 13 RequiredService objects. A RequiredService is a special kind 14 of Service. A
Service has a type and a name. In addition, a RequiredService also has a serviceState. This
serviceState indicates whether the RequiredService is not yet serviced by any station, is
pending to be serviced by some station, or is already serviced. A RequiredService can
change state by execution of the methods (transformers) that correspond to the messages
markUnserviced, markPending and markPerformed.
11 Aggregation is indicated by the symbol.
12 The zero or one arity is indicated by the ¡ symbol.
13 The zero or more arity is indicated by the ¢ symbol.
14 The generalisation/specialisation relation is indicated by the £
symbol.