Linda is a concept for process communication.
For an introduction and a deeper description, see [Carreiro & Gelernter 89a] or [Carreiro & Gelernter 89b], respectively.
One process is running as a server and one or more processes are running as clients. The processes are communicating with sockets and supports networks.
The server is in principle a blackboard on which the clients can write
out/1), read (
rd/1) and remove (
in/1) data. If
the data is not present on the blackboard, the predicates suspend
the process until they are available.
There are some more predicates besides the basic
rd_noblock/1 does not suspend if the data is not available—they
fail instead. A blocking fetch of a conjunction of data can be done
Example: A simple producer-consumer. In client 1:
producer :- produce(X), out(p(X)), producer. produce(X) :- .....
In client 2:
consumer :- in(p(A)), consume(A), consumer. consume(A) :- .....
..., in(ready), %Waits here until someone does out(ready) ...,
Example: A critical region
..., in(region_free), % wait for region to be free critical_part, out(region_free), % let next one in ...,
Example: Reading global data
..., rd(data(Data)), ..., or, without blocking: ..., rd_noblock(data(Data)) -> do_something(Data) ; write('Data not available!'),nl ), ...,
Example: Waiting for one of several events
..., in([e(1),e(2),...,e(n)], E), % Here is E instantiated to the first tuple that became available ...,