About component architectures...

Some thoughts about component architectures...
(Feedback is _very_ welcome!)

Some initial description about the set of generic Orocos component
architectures has already been given in the minutes of the Toulouse
meeting, but more discussion and fine-tuning is necessary, I think.

In the three component architectures we mentioned (Feedback control,
Robotic service, Autonomous system), we always seem to come up with a
`supervisor': the subcomponent that ``knows all'' about the component,
and that configures the other sub-components, and gives them work to
do.

I am not too happy with a `supervisor' because that is such a general
name that covers too many different things we want to separate. For
example, I think that, in terms of Software Patterns, the `supervisor'
is really two things:

- Configurator (what the people in LAAS call ``control flow'' I guess),
  which takes care of the proper initialization of its internal
  sub-components and their communication.
  A key property of a configurator  is that it intervenes _only once_
  (per configuration action) for the objects or components that it
  configures.

- Mediator (``data flow'') that accepts service requests from
  the user and divides those into actions for its sub-components.
  A key property of a Mediator is that it intervenes in _every_
  interaction between the objects or components it mediates. This seems
  the case to me for all service requests that enter the component.

Maybe it's even more, but I hope not, in order to keep things simple.

Should we make separate sub-component for each of these ``roles'' or
should we do just that: call it supervisor, and give it different
roles (Configurator, Mediator) to play?

I hope (and am quite sure) to be able to use existing Software Pattern
names as much as possible, because this helps a lot in documenting
what we mean.

How much of all this is really generic for _all_ the components we need?

Herman

-- 
K.U.Leuven, Mechanical Engineering, Robotics Research Group
<http://www.mech.kuleuven.ac.be/~bruyninc>  +32 16 322480