Re: [Playexrstage-developers] Common robotics data exchange format...?

On Fri, 13 Aug 2004, Brian Gerkey wrote:

> On Fri, 13 Aug 2004, Herman Bruyninckx wrote:
>
>> I'm responsible for the Orocos project, <http://www.orocos.org>, and
>> one issue that surfaces in most of my discussions with contributors to
>> open source robotics projects is the standardisation of "objects" and
>> the protocols to exchange such objects in distributed systems.
>
> hi Herman,
>
> This is an enormous and ambitious undertaking, and we've already
> seen the failure of at least one concerted effort at it: the RETF
> (http://www.robo-etf.org/).
>
> The goals of the RETF were very much what you've mentioned: specify
> standards for interchange of commands and data for every kind of robot
> device.

I know, and that's way I explicitly limit the ambition to data
structures only (and also of _robots_ only, not (in a first stage)
sensors, shape, etc.). Certainly no protocols, or no APIs, because
both of these belong to _architectures of applications_ and not to the
pure data in a system. Trying to get these two out of each other's field
of view was (and still is) one of the main motivations behind Orocos :-)

> They also started with the Player interface spec.  There was
> an active mailing list for several months (which I think you, Herman,
> were also on), 
Yes, but I was never too excited about it. But their draft does remain
something to take into account very seriously.

> The group got bogged down immediately in questions like: Do we make
> a "specification" or an "API"?  How do we define devices? What's
> the right level of abstraction?  Do we exchange data is a tight
> binary format or XML?  We lacked a consensus on any of these issues.
Exactly! I do not want to get involved in these discussions: they will
follow naturally _after_ projects start to use the data structure
standard. (_If_ they do :-)

> One immediately obvious problem was that the people who build systems from
> microcontrollers and PWM motors have a distinctly different worldview from
> those who use off-the-shelf research robots that carry workstation-class
> computers (in my opinion, this particular chasm cannot be bridged).
I agree. I want to focus on the latter type of robotics.

>   (i) Be less ambitious.  We've done well with Player, not by identifying
>       how to interact with all possible devices, but by handling the
>       obvious ones, and then being flexible and inclusive, considering
>       and incorporating each new kind of device as it comes along.
>       If we set out to "cover all thinkable robot structures," we'd
>       never actually write any software.
We don't have to write any software :-) And with "robotic structures" I
just meant the kinematic structure, i.e., specifying the joint and
Cartesian motion capabilities of the devices, nothing more. As I said
before: no sensors, etc.

>  (ii) Have discussion, but assert control.  Not everybody will like your
>       standard, but don't worry about them.  I believe community
>       consensus on this topic to be unattainable, and one of the
>       frailties of the RETF was that it lacked any authority figure
>       (which could be either an individual or a small group) to actually
>       make decisions.  As a result, discussion ranged far and wide,
>       with little in the way of tangible results.
I agree here also. And my concrete suggestion is: _you_ will be the
controlling "authority", i.e., Player/Stage decides what they want to
use, and the other projects follow or leave. The reason for this is
simple: you're the only one with a world-wide and broad user base.

[...]
> Another popular system is CARMEN, from CMU/Stanford/MIT:
>  http://www-2.cs.cmu.edu/~carmen/
> In my experience, the CARMEN folks are less interested in standards-making
> than some other projects, but it would be remiss to leave them out.
No problem with that.

> To be clear, I don't mean to sound overly pessimistic about this idea;
> I just don't want to see a repeat of the RETF....
I think we are on the same wavelength :-)

Herman

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


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