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

6.6 Dynamic Behaviour 217
to happen. If S p
1
is aborted, its rest statements are not executed. If Sp
1 terminates
successfully the complete statement terminates and S p
2 is not executed at all.
11. The interrupt statement S p
1 interrupt S p
2 enables breaking in on the execution of S p
1
with alternative statement S p
2
execution and the execution of S p
1
. The interruption happens if Sp2
can be taken into
arrived at a transition between two statements
where interruption is allowed to happen. If S p
1 is interrupted its rest statements
are executed after S p
2 terminates successfully. S p
2 is not executed if S p
1 terminates
successfully.
6.6.7 Modelling System Level Behaviour
6.6.7.1 Cluster Class Specification
A cluster is a domain boundary around a group of collaborating process objects and/or
clusters. The behaviour of a cluster is specified in a cluster class definition, which is
typically:
cluster class Cc ¡ ¥ ¡ ¥¡ ¡
¡ ¡
P1 Pr
communication channels
message interface
ch1 chk
l p
1 ¡ ¡ lp behaviour specification
m
BSpecp The first element is the declaration of the cluster class name C. P1 ¥¡ ¡ ¡ ¥ Pr are so-called
expression parameters. They are bound to data expressions when the cluster is instantiated.
The channels of a cluster are defined by ch1 ¡ ¡ chk. The possible communication of a
cluster is determined by its message interface, l p
1 ¡ ¡ lp m. This message interface has the
same meaning as in the case of process objects.
A cluster contains an internal structure of one or more process objects and clusters. Its
behaviour is completely determined by its internal objects. The behaviour description
BSpec p is typically a composition of parameterised behaviour specifications of process objects
and/or clusters. BSpec p is of one of the following forms:
C p (PE1 ¥¡ ¡ ¡ ¥ PEr)
C c (PE1 ¥¡ ¡ ¡ ¥ PEr)
BSpec p
1
BSpecp BSpecp f §
BSpecp2
¢
L
Cp ¥¡ ¡ ¡ ¥ (PE1 PEr) denotes a single instance of a process class Cp ¡ ¡ ¥ yr ¡ . The
y1¥¡
instance variables ¥¡ ¡ ¡ ¥ y1 yr are initialised to the results of the evaluation of the parameterised
data expressions PE. A parameterised data expression is a data expression that
contains expression parameters. These parameterised data expressions are described in
detail in Section 9.2.
C c (PE1 ¥¡ ¡ ¡ ¥ PEr) denotes a single instance of a cluster class. A cluster contains at least an
instance of a process class or an instance of another cluster class. In general however,