Re: [ontolog-forum] Constraint Solving versus Inferencing

["Rich Cooper" <rich@xxxxxxxxxxxxxxxxxxxxxx>]

There was an article in Artificial Intelligence called “Constraint Propagation”, which is, IMHO, the most useful form of constraint solver.  I don’t remember the month or year of that issue.  Does anyone else remember that?

 

If you google “constraint propagation algorithm”, there are several pages of tutorial and scholarly links that sound worth pursuing if you are just learning about the topic.  I find constraint propagation intensely useful in solving day-to-day problems; it’s a way of thinking that helps order your thoughts.  It also expresses your solutions to problems much more elegantly, and therefore more understandably. 

 

But note that a constraint solver need not be “iterative” in the sense of improving estimates step-by-step till they converge.  Constraints can be expressed in simple Boolean logic, or in full blown first order logic.  It’s the way you trade off one constraint for another that improves the global system of constraints, but there is often a true minimal cost or maximal gain solution to systems of constraints.  It is well worth reading about. 

 

-Rich

 

Sincerely,

Rich Cooper

EnglishLogicKernel.com

Rich AT EnglishLogicKernel DOT com

9 4 9 \ 5 2 5 - 5 7 1 2

From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx [mailto:ontolog-forum-bounces@xxxxxxxxxxxxxxxx] On Behalf Of Simon Spero
Sent: Friday, October 10, 2014 9:41 AM
To: [ontolog-forum]
Subject: Re: [ontolog-forum] Constraint Solving versus Inferencing

 

See eg http://en.m.wikipedia.org/wiki/Constraint_logic_programming

On Oct 10, 2014 11:16 AM, "David Whitten" <whitten@xxxxxxxxxx> wrote:

Since we have such a large group of mathematically sophisticated people on this mailing list, I'd like to open a topic I know little about.

I recently learned there is a Constraint Solver based on this paper

http://constraints.cs.washington.edu/solvers/cassowary-tochi.pdf

Described as software here:

https://www.npmjs.org/package/cassowary

with the implementation at the github address:

https://github.com/slightlyoff/cassowary-js-refactor

From their description:

Constraint solvers are iterative algorithms that work towards ever more ideal solutions, often using some variant of Dantzig's simplex method. They are primarily of interest in situations where it's possible to easily set up a set of rules which you would like a solution to adhere to, but when it is very difficult to consider all of the possible solutions yourself.

One of the things Inference Engines allow as the internal software of an expert system is to calculate the logical closure (those facts which can be inferred from an axiom set and a set of rules).

Are these two approaches compatible?

 

Is the Simplex method only useful for operational research, or is it useful in logical operations on ontologies ?

 

Best

 

David Whitten

713-870-3834

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