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

6.3 Communication 185
6.3.10.2 Description of Data Object Communication
The description of a message to a data object in POOSL does not have the rendezvous
character like the communication among process objects. The description is limited to
an expression in the sender. There is no explicit receive statement. The message name is
immediately coupled to a method that must be executed at the receiver side on reception
of the message. The reply to the sender is implicitly sent when the method execution
terminates. A message-send expression is of the form:
E m(E1 ¥¡ ¡ ¡ ¥ En)
E is an expression that evaluates to a reference to a data object. This data object receives
message m with parameters E1 ¥¡ ¡ ¡ ¥ En. The reception of message m causes the execution
of the corresponding method m in the data object. When the execution is finished the
result is returned. The semantics are that the initial send expression is replaced by the
result. For instance:
x : E m(E1 ¥¡ ¡ ¡ ¥ En)
means that the result of the message is assigned to variable x.
6.3.10.3 Summary
We selected a collection of sorts of communication:
1. synchronous communication with reply and waiting;
2. synchronous communication with reply, waiting and time-out;
3. synchronous communication with reply but without waiting;
4. synchronous communication without reply;
5. asynchronous communication without reply;
6. asynchronous communication with reply (and time-out);
7. continuous communication;
8. interrupting communication;
8. interrupting communication with reply;
9. broadcast communication;
10. multicast communication.
This collection is sufficient to describe a wide variety of systems. Especially the interrupt
distinguishes our method. POOSL offers an abort as well as an interrupt construct to
support interrupting communication. This gives abilities for the description of the
interruption of concurrent (infinite) behaviour, and for modelling hardware interrupt
mechanisms.