SDL-News: Transition atomicity and tool behavior

Subject: SDL-News: Transition atomicity and tool behavior
Date: Tue Apr 29 1997 - 19:45:20 GMT

The originator of this message is responsible for its content.

-----From Philippe Leblanc <> to sdlnews -----

Following previous emails on transition atomicity, this is

how the ObjectGEODE Simulator operates:

Process transitions (from an input to a next state)

are executed in an atomic way. It means that

as soon as a transition is fired, all the actions (tasks, outputs,

timer sets, etc.) are performed within the same step.

When the next state is reached, the simulator evaluates

all the fireable transitions (a fireable transition roughly

corresponds to the presence of a consumable signal in a

process queue or a continuous signal set to true).

In Interactive mode, the human operator selects the transition

he/she wants to fire. In Exhaustive mode (for validation

purpose), the simulator will investigate ALL the combinations.

It means that in a given system state, if 3 independent transitions

are fireable, the simulator will build 6 (= 3!) paths in the system

state graph, corresponding to all the possible combinations.

Note 1: Import expressions introduce intermediate states.

Note 2: We have added a priority mechanism between

processes that reduces possible combinations of

transition executions.

Note 3: Process queues can be bounded in the Simulator

by means of so-called filter conditions.

So, in the OG Simulator, the process instances run in a

pseudo-parallelism mode -- there is no interleaving

between transition symbols - but the interleaving is

completely taken into account at transition level.

Hope that helps, and sorry for this late answer.

Philippe Leblanc


Tel.: +33 (0)5 61 19 29 33

Switchboard: +33 (0)5 61 19 29 39

Fax: +33 (0)5 61 40 84 52



BP 1310

F-31106 Toulouse Cedex - France

-----End text from Philippe Leblanc <> to sdlnews

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