A brief and non-technical description of the two types of semantics mentioned in the previous discussions:
(1) Model-Theoretic Semantics (MTS) (1.1) There is a world existing independently outside the intelligent system (human or machine). (1.2) In principle, there is an objective description of the world, in terms of objects, their properties, and relations among them. (1.3) Within the intelligent system, its knowledge is an approximation of the objective description of the world. (1.4) The meaning of a symbol within the system is the object it refers to in the world. (1.5) The truth-value of a statement within the system measures how close it approximates the fact in the world. (2) Experience-Grounded Semantics (EGS) (2.1) There is a world existing independently outside the intelligent system (human or machine). [same as (1.1), but the agreement stops here] (2.2) Even in principle, there is no objective description of the world. What the system has is its experience, the history of its interaction of the world. (2.3) Within the intelligent system, its knowledge is a summary of its experience. (2.4) The meaning of a symbol within the system is determined by its role in the experience. (2.5) The truth-value of a statement within the system measures how close it summarizes the relevant part of the experience. To further simplify the description, in the context of learning and reasoning: MTS takes "objective truth" of statements and "real meaning" of terms as aim of approximation, while EGS refuses them, but takes experience (input data) as the only thing to depend on. As usual, each theory has its strength and limitation. The issue is which one is more proper for AGI. MTS has been dominating in math, logic, and computer science, and therefore is accepted by the majority people. Even so, it has been attacked by other people (not only the EGS believers) for many reasons. A while ago I made a figure to illustrate this difference, which is at http://nars.wang.googlepages.com/wang.semantics-figure.pdf . A manifesto of EGS is at http://nars.wang.googlepages.com/wang.semantics.pdf Since the debate on the nature of "truth" and "meaning" has existed for thousands of years, I don't think we can settle down it here by some email exchanges. I just want to let the interested people know the theoretical background of the related discussions. Pei On Sat, Oct 11, 2008 at 8:34 PM, Ben Goertzel <[EMAIL PROTECTED]> wrote: > > > > Hi, > >> >> > What this highlights for me is the idea that NARS truth values attempt >> > to reflect the evidence so far, while probabilities attempt to reflect >> > the world > > I agree that probabilities attempt to reflect the world > >> >> . >> >> Well said. This is exactly the difference between an >> experience-grounded semantics and a model-theoretic semantics. > > I don't agree with this distinction ... unless you are construing "model > theoretic semantics" in a very restrictive way, which then does not apply to > PLN. > > If by model-theoretic semantics you mean something like what Wikipedia says > at http://en.wikipedia.org/wiki/Formal_semantics, > > *** > Model-theoretic semantics is the archetype of Alfred Tarski's semantic > theory of truth, based on his T-schema, and is one of the founding concepts > of model theory. This is the most widespread approach, and is based on the > idea that the meaning of the various parts of the propositions are given by > the possible ways we can give a recursively specified group of > interpretation functions from them to some predefined mathematical domains: > an interpretation of first-order predicate logic is given by a mapping from > terms to a universe of individuals, and a mapping from propositions to the > truth values "true" and "false". > *** > > then yes, PLN's semantics is based on a mapping from terms to a universe of > individuals, and a mapping from propositions to truth values. On the other > hand, these "individuals" may be for instance **elementary sensations or > actions**, rather than higher-level individuals like, say, a specific cat, > or the concept "cat". So there is nothing non-experience-based about > mapping terms into a "individuals" that are the system's direct experience > ... and then building up more abstract terms by grouping these > directly-experience-based terms. > > IMO, the dichotomy between experience-based and model-based semantics is a > misleading one. Model-based semantics has often been used in a > non-experience-based way, but that is not because it fundamentally **has** > to be used in that way. > > To say that PLN tries to model the world, is then just to say that it tries > to make probabilistic predictions about sensations and actions that have not > yet been experienced ... which is certainly the case. > >> >> Once >> again, the difference in truth-value functions is reduced to the >> difference in semantics, what is, what the "truth-value" attempts to >> measure. > > Agreed... > > Ben G > > ________________________________ > agi | Archives | Modify Your Subscription ------------------------------------------- agi Archives: https://www.listbox.com/member/archive/303/=now RSS Feed: https://www.listbox.com/member/archive/rss/303/ Modify Your Subscription: https://www.listbox.com/member/?member_id=8660244&id_secret=117534816-b15a34 Powered by Listbox: http://www.listbox.com
