RE: Rule of Least Power

From: Roy T. Fielding [mailto:fielding@gbiv.com]

>... declarative communication improves
>visibility of interactions, which in turn enables greater evolvability
>as the participants in the communication change over time.  

That sums it up nicely.  It is Panglossian but ok.  You 
tend to think of the social system in purely network 
concepts.  It is a useful point of view but only one.

Subjective systems are systems that provide for 
multiple points of view over the same information. 
The key is scope and context and thus the Airbus example. 
All signals are not equally visible.  See below.

I agree that calling it a rule is mislabeling. 
I say it is a weak rule because the closer to 
application context, the weaker it becomes. 
That's ok.  It is in effect, an example of itself.

"The web is a social system...".  Social systems 
are coupled to economic systems.  If the economic 
systems don't provide social benefits, they fail 
over time (your years over hours model).

Going a bit off topic here but...

Because the web is a social system, failing to 
reckon with the economic aspects or social 
disturbances is a recipe for disaster.  For 
example, do you still trust your cellphone 
provider with your social security number?

1. time of acquisition of signal is immediate; 
2. time to sale of signal is near real time; 
3. time to notification of identity theft is 
   the fastest notification of the defaulting 
   transaction (usually a credit bureau) and 
   that is too slow given the damage done and 
   mitigation time and resources required.   

Thus, weak means are inadequate.  

The web as a feedback system 
creates oscillations in the social systems 
and the economic systems if the social system 
is vulnerable (how much do you think the guy 
taking the order for your phone makes a week 
vs what he or she will be paid for a collection 
of fresh SSNs - it is identity theft payola).

Better at this point to quit using SSNs and to 
strengthen the business rules by some means.

See PID.  You really should.  It will broaden 
your design horizons.

len



Thus,
an analysis that talks about the run-time operation of a short-lived
or closed system (like Airbus) is not going to encounter any benefits
from the design principle.  In order to get the benefits you have to
look at the system as it evolves over the scope of years, not hours,
and independent of any "flag-day" decisions wherein one organization
decides it is time to upgrade.

> I think you ignore that subjective systems
> can be globally stable but create local instabilities.

I am afraid I don't know what you mean by subjective systems.  The Web
is a social system and one of its design goals is to remain globally
stable while encouraging local innovations.

> As a context, the web is global.  As a rule, RLP is
> second-order friendly (a subjective or observer-based
> cybernetic system).  So far so good, but applying that
> rule locally can create instabilities.

It is a design principle, not the answer to every question.  I think it
would be helpful if folks were directed to the Principle of Least  
Authority
that I described back in

   http://lists.w3.org/Archives/Public/www-tag/2005Dec/0032.html
   http://szabo.best.vwh.net/interpretingpower.html

because that also is a design principle that places long-term safety
(knowing that change is inevitable) over short-term efficiency.

> The trick is to tune it, Roy.  See PID controls.
>
> The business intelligence guys are way out front
> on this one.

Umm, no, I think that completely misses the point.

....Roy

Received on Wednesday, 8 March 2006 16:43:33 UTC