# Rules vs. Lists

A. Katz amnfn at well.com
Thu Jul 3 13:32:03 UTC 2008

```Rob,

No, I am not implying there is a vast body of literature on this topic. My
assurance comes from logic. A list is a set of rules with a single example
of the application of each rule. When we speak of a rule-based system,
we mean one each rules has many examples of its application. When
we speak of list-based system, we speak of a system where there are more
rules than instances where they are applied.

For instance, the multiplication table can be described either way. We can
memorize each entry and describe it as a list. Or we can give a single
rule, x  times y is x plus x y times. They are functionally equivalent.
You can get the right answer either way. But when we make a separate rule
for each instance, we call that listing. When we allow a single rule to
cover many instances, we call that rule-based.

It's doesn't take any previous literature to determine this is so. It is
so by definition. It's a tautology.

Best,

--Aya

The grammar of a language could

On Thu, 3 Jul 2008, Rob Freeman wrote:

> Aya,
>
> You seem to be implying there is already a large body of literature
>
> Do you have any references for what you describe as "list-based"
> systems ("more rules than examples of their application"), in
> particular with reference to language?
>
> For the system to be non-trivial the rules should be implicit in the examples.
>
> I particularly want to think about what such a system would look like
> from the point of view of the examples (e.g. surely it would mean each
> example would be subject to interpretation in more than one way, a
> given interpretation dependent on context, etc.)
>
> -Rob
>
> On Wed, Jul 2, 2008 at 9:18 PM, A. Katz <amnfn at well.com> wrote:
> > Rob,
> >
> > Here is where the concept of "functional equivalence" is very helpful. If
> > two ways of describing a phenomenon give the same results, then they are
> > functionally equivalent. That means that in essence, they are the same --
> > at least as far as results of calculation are concerned. (Considerations
> > of processing limitations might show that one works better for a given
> > hardware configuration than another, but that is a somewhat different
> > issue.)
> >
> > Rules and lists are functionally equivalent. Logically speaking, they are
> > the same.
> >
> > When there are more rules than examples of their application, we call it a
> > list-based system. When there are many more examples of the application of
> > a rule than different rules, then we call it a rule-based system.
> >
> > That's just about different methods of arriving at the same result, and is
> > strictly a processing issue. In terms of describing the language, rather
> > than the speakers, however, there is no difference. It's all the same.
> >
> > In order to appreciate this, we have to be able to distinguish the
> > structure of the language from the structure of the speaker.
> >
> > Best,
> >
> >
> >    --Aya
>
>

```