Hi Benoit
This is basically what "publish and subscribe" schemes are all about. Linda is
a simple "coordination protocol" for organizing such loose couplings. There are
sketches of such mechanisms in most of the STEPS reports ....
Spreadsheets are simple versions of this
The Playground language for the Vivarium project was set up like this
For real scaling, one would like to move to more general semantic descriptions
of "what is needed" and "what is supplied" ...
Cheers,
Alan
>________________________________
> From: Benoît Fleury <[email protected]>
>To: Fundamentals of New Computing <[email protected]>
>Sent: Monday, March 19, 2012 1:10 PM
>Subject: [fonc] Naive question
>
>
>Hi,
>
>
>I was wondering if there is any language out there that lets you describe the
>behavior of an "object" as a grammar.
>
>
>An object would receive a stream of events. The rules of the grammar describe
>the sequence of events the object can respond to. The "semantic actions"
>inside these rules can change the internal state of the object or emit other
>events.
>
>
>We don't want the objects to send message to each other. A bus-like structure
>would collect events and dispatch them to all interested objects. To avoid
>pushing an event to all objects, the "bus" would ask first to all objects what
>kind of event they're waiting for. These events are the possible alternatives
>in the object's grammar based on the current internal state of the object.
>
>
>It's different from object-oriented programming since objects don't talk
>directly to each other.
>
>
>A few questions the come up when thinking about this:
> - do we want backtracking? probably not, if the semantic actions are
>different, it might be awkward or impossible to undo them. If the semantic
>actions are the same in the grammar, we might want to do some factoring to
>remove repeated semantic actions.
> - how to represent time? Do all objects need to share the same clock? Do we
>have to send "tick" events to all objects?
> - should we allow the parallel execution of multiple scenarios for the same
>object? What does it make more complex in the design of the object's behavior?
>What does it make simpler?
>
>
>If we assume an object receive a tick event to represent time, and using a
>syntax similar to ometa, we could write a simplistic behavior of an ant this
>way:
>
>
># the ant find food when there is a food event raised and the ant's position
>is in the area of the food
># food indicates an event of type "food", the question mark starts a semantic
>predicate
>findFood = food ?(this.position.inRect(food.area))
>
>
># similar rule to find the nest
>findNest = nest ?(this.position.inRect(nest.area))
>
>
># at every step, the ant move
>move = tick (=> move 1 unit in current direction (or pick random
>direction if no direction))
>
>
># the gatherFood scenario can then be described as finding food then finding
>the nest
>gatherFood = findFood (=> pick up food, change direction to nest)
> findNest (=> drop food, change direction to food source)
>
>
>There is probably a lot of thing missing and not thought through.
>
>
>But I was just wondering if you know a language to do this kind of things?
>
>
>Thanks,
>Benoit.
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>
>
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