Dear Matthew, (01)
I am strongly in favor of using a 4D coordinate system for knowledge
representation and reasoning. For modern physics, a 4D system is
essential. For databases and knowledge bases, it simplifies many
problems. One of my favorite philosophers, Alfred North Whitehead,
used a 4D system for his ontology, which is one of the few that is
sufficiently general to support both modern physics and common sense. (02)
But any information about the future that "seems" to come from
an extensional analysis of some 4D region is always derivable
from the intensional specifications that determine or predict
those possible worlds (or those spatio-temporal regions). (03)
> MW: In a 4D analysis a plan is a set of actions (spatio-temporal
> extents) in a possible world. The goal to be achieved is a state
> of affairs in that possible world at a point in time. It does not
> matter that they are in the future, the plan is the actions you
> intend to take, not the desired outcome. (04)
I like your last sentence, which uses the word 'intend'.
It shows that the origin of the information is the *intention*
(with a T), which determines the *intension* (with an S),
which determines the *extensions* in those possible worlds. (05)
But I disagree that "a plan is a set of actions". Whether you're
using a 4D analysis or 3+1D is irrelevant to the definition of 'plan'. (06)
As I suggest to anybody who works on knowledge representation or
ontology, consult a good dictionary for a neutral (i.e., non-dogmatic,
not theory laden) opinion about the way words are commonly used. (07)
For example, the Merriam-Webster 9th Collegiate Dictionary says
that the word 'plan' comes from the same Latin root as the word
'plane'. That origin leads to MW definition #1: (08)
> 1. a drawing or diagram drawn on a plane. (09)
We've all seen plans for houses that specify the goal to be
achieved or the result that was achieved, but not the actions. (010)
Definition #2 is derivative from that primary meaning.
It has four variants: (011)
> 2a. a method for achieving an end
>
> 2b. an often customary method of doing something, procedure
>
> 2c. a detailed formulation of a program of action
>
> 2d. goal, aim (012)
Definitions #3 and #4 are special cases of #2: (013)
> 3. an orderly arrangement of parts of an overall
> design or objective
>
> 4. a detailed program (as for payment or provision of
> some service). Example: pension plan (014)
Following the definitions are 5 synonyms: plan, design, plot,
scheme, project. It says that all five words "mean a method
devised for making or doing something or achieving an end". (015)
That dictionary also says the word 'plan' "always implies
mental formulation and sometimes graphic representation."
All these definitions say that a plan is a goal or a method.
None of them identify a plan with the sequence of actions. (016)
If you prefer a British view, following are the four senses
of 'plan' in the Longman Dictionary of Contemporary English: (017)
> 1. a (carefully considered) arrangement for carrying out
> some future activity.
>
> 2. an arrangement of the parts of a group or of a system.
>
> 3. a line drawing of a building or room as it might be
> seen from above.
>
> 4. [usually plural] a set of drawings, with measurements,
> showing the parts of a machine. (018)
Both dictionaries emphasize the goal (or a drawing of the goal)
and the intentions that led to the goal: a plan "always implies
mental formulation", and the arrangement is "carefully considered". (019)
> MW: A sequence of action (types) is a method, but not a plan.
> A plan may be a particular execution of a method (but not
> necessarily). (020)
Please note that both dictionaries define a plan as either
a goal or a method for achieving the goal. I have never
heard anybody use the word 'plan' in the way you describe. (021)
To be consistent with normal English usage, I suggest that
you use the term 'execution of a plan' for the sequence
of actions in your possible worlds. (022)
Another comment about word usage: (023)
> JFS: The specifications of the plan could be called axioms,
> constraints, or laws.
>
> MW: No. What is often the case is that the constraints
> (resource availability, time, materials) are inputs to
> formulating a feasible plan (I think of linear programming
> in the oil industry). However, the constraints are not
> the plan itself. (024)
My primary word was 'specifications'. They determine the methods
the dictionaries mention. There are two ways to specify a method: (025)
1. Procedural: An ordered sequence of imperative commands,
as in a typical programming language. (026)
2. Declarative: A set of propositions that state the starting
conditions (prerequisites) and ending conditions (desired
goal) for any procedure that implements the method. (027)
A procedural specification is useful for efficient execution
by a specific machine or by a human agent who is not expected
to innovate or to deviate from a fixed sequence. (028)
A declarative specification is more general, since it covers
an open-ended variety of procedures that begin with the starting
conditions and end with the desired goal. It allows greater
flexibility in changing the order of execution and adapting
to unforeseen circumstances. But it does require a more
intelligent machine or human. (029)
I used the words 'axioms', 'constraints', or 'laws' for the
propositions that state the preconditions and postconditions
of a declarative specification. I am happy to replace those
words with any other way of talking about the propositions. (030)
I'll admit that people rarely use the terminology of logicians
or computer scientists to talk about their planning sessions.
But you can analyze their informal discussions and classify
their ways of describing plans as procedural, declarative,
or some informal mixture of both. (031)
John (032)
_________________________________________________________________
Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/
Config Subscr: http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/
Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
Shared Files: http://ontolog.cim3.net/file/
Community Wiki: http://ontolog.cim3.net/wiki/
To join: http://ontolog.cim3.net/cgi-bin/wiki.pl?WikiHomePage#nid1J (033)
|