quote:Original post by Nathaniel Hammen
Actually Fuzzy Logic could work, if you had the certainty represented by a fuzzy variable. 1.0 meaning absolutely certain and 0.0 meaning not certain at all. But I do agree that fuzzzy logic is not very useful for the task. I just wated to point out that it COULD be used.

How is what you''re describing as Fuzzy Logic any different from the way I was describing FL as logical uncertainty?

quote:You know what? More and more, I want to get my hands on a copy of AI Game Programming Wisdom. I want to buy it, but I don''t want to pay $50 for a book, when I am living off of my parents good will.

Step 1) Get a Job
Step 2) www.amazon.com

What is this, my fourth post in a row? Sorry guys.

quote:Original post by Timkin
Given the recent discussions, I think you really should take a look at NAG. It might be a good first project to create the argumentation and inference mechanism for the NPC.

As luck would have it, NAG just isn''t a specific enough term for Google to give me any useful results. Can''t imagine why. Can you give me more info? Or a URL, if that''s not too much to ask?

A lot of people misunderstand FL. Fuzzy logic is deterministic. The membership value (between 0 and 1) of an element to a fuzzy set represents the confidence of its membership to that set, not the probability.



My Website: ai-junkie.com | My Book: AI Techniques for Game Programming

quote:Original post by Timkin
irbrian, FL is about logic... and you are correct, it''s a logic in which there are other values besides 0 and 1. But this is all set theory... As fup pointed out, the membership value is not a probability or likelihood of membership in a set. It''s a degree as to how much the item belongs to that set. In Aristotlean logic, items belong to one set or another. Statements are either true or false. In Fuzzy logic, statements can be partly true and partly false at the same time . This, however, has absolutely nothing to do with uncertainty in a statement. Fuzzy logic makes statements about things in the world. Uncertainty formalisms - such as Bayesian probabilities - make statements about the what we believe to be true or false in the world. Consider an example satement: John is a thief. Uncertainty in this statement might be represented by saying that there is a 70% chance that this statement is true. Fuzzy logic however would say that either John is a Thief, John is not a Thief, or to some degree, John is both a Thief and not a Thief.

Do you see the distinction?

I think I''m beginning to see the distinction now... Fuzzy Logic is about propositions being both true and false to some degree. I.E., "It is sort of hot outside" can be interpreted as "It is hot outside AND It is not hot outside." To account for degree of truthfulness, the statements are represented by a value between 0.0 and 1.0, I.E. the first proposition "It is hot outside" might be a 0.6 and the second "It is not hot outside" might have a value of 0.4.

Thus, considering the following two statements:
A) "John is sort of a thief."
B) "John might be a thief."

You are suggesting that proposition A is Fuzzy Logic, because John is both a thief and not a thief; and proposition B is more of, I dunno, a boolean probability I guess you could say.

If I''m understanding so far, I''ll re-evaluate my original statement:
"I believe someone has robbed my store."

Perhaps then this would be best broken into two statements:
A) "I believe that my store was robbed.
B) "Someone robbed my store."

Seems to me the following is true:
1. The evaluation of B is predicated upon the truthfulness of A.
2. A is a boolean probability:
There is a high probability the store was robbed.
3. B is neither probability not fuzzy logic, because its not a true or false value. It is simply an unknown, a variable -- a Question Needing an Answer in the mind of the NPC.

Alright.. I think I get it now. Someone please tell me I''m wrong.. otherwise thanks for the clarification.

Anyway so my original point was that NPCs never have enough information to form absolute conclusions about things.

That said, does Fuzzy Logic still comes into play? How exactly do NPCs handle the situation when they acquire conflicting information?

Given that the NPC Frank has no opinion yet on the subject, consider the following Observations:
A) "Sal believes that John is a thief."
B) "Joe believes that John is not a thief."

So how would this be best handled in order for the NPC to begin to form an opinion?
1) "It is believed that John is a thief (50%) AND It is believed that John is not a thief. (50%)" (True FL)
2) "John might be a thief. (50%)" (Probability)
3) "I trust Joe more than I trust Sal. THUS, John is a thief (0.4) AND John is not a thief (0.6)." (FL, with weighted inputs)
4) "I trust Joe more than I trust Sal. THUS, it is probable that John is not a thief." (Probability, weighted)
etc.

I would use fuzzy logic, but not for the beleifs or the memories, but for the personality. "The pre-generation of John''s character defined him as greedy, lazy, opportunistic, sneaky, and cowardly, yet charismatic." In other words, John has a greedyness of 0.99, activeness of 0.05, etc... Values closer to 0.5 would represent more normal people, and extremes would represent people who would have a larger impact on this "civilization." Since almost all of John''s stats are extreme, it is expected that he would have a large impact on this city, which is just what happened in your scenario.

--------------------------------------
I am the master of stories.....
If only I could just write them down...

quote:Original post by Timkin

quote:Original post by irbrian
and proposition B is more of, I dunno, a boolean probability I guess you could say.

No. Boolean suggests only 1 of two mutually exclusive values. That would be First Order (Aristotlean) logic. Probabilities are values in the range of [0,1] of a variable that satisfies the axioms of probability.

Alright, so boolean probability is a contradiction. You didn''t state it, but it seems clear that prop. B in that case was an issue of probability. Incidentally, unless its a common usage, I wouldn''t define probability as a range of values [0,1] as that really causes some confusion with the whole Fuzzy Logic 0.0-1.0 thing. Can''t we just use percentages for probability like the rest of the world and make the distinction as clear as possible?

quote:

quote:Perhaps then this would be best broken into two statements:
A) "I believe that my store was robbed.
B) "Someone robbed my store."

This is a hard example to deal with, because it''s really hard to describe how a store was both robbed and not robbed. It''s a little nonsensical. However, given this example, I would personally write it as:

A) My store was sort of robbed
...
A) Is clearly now a statement suggesting that the store was both robbed and not robbed.

Ugh, now you''re trying to turn it back into Fuzzy Logic. I thought we agreed to stay AWAY from Fuzzy Logic in this case, as I now agree that it really doesn''t apply. Seems to me it''s a simple case of probability. What you''re saying up there simply doesn''t make any sense at all -- FL strikes me as a statement of fact just as Boolean logic is a statement of fact. Of course it''s possible I''m totally off-base (and I''m sure you''ll correct me if I am), but I don''t think even FL should allow two mutually exclusive conditions to co-exist.

Going back to probability-based beliefs, we could say that at a certain level of probability, an NPC forms a belief that something is about something is true, even though the NPC will never understand something to be 100% true. For instance:

0-10% --- Invalid Range for Belief formed by AI
10-20% -- NPC Believes the proposition is FALSE
21-40% -- NPC Believes the proposition is "probably FALSE"
41-60% -- NPC Believes the proposition is EITHER True OR False -- NOT True AND False.
61-80% -- NPC Believes the proposition is "probably TRUE"
81-90% -- NPC Believes the proposition is TRUE
91-100% - Invalid Range for Belief formed by AI

quote:

quote:Seems to me the following is true:
1. The evaluation of B is predicated upon the truthfulness of A.

Not necessarily. While it may be true that the store was not robbed, an agent can hold false beliefs. That is, they can beliefve something to be true,even though in reality, it is not true (and vice versa).

I agree that NPCs can believe something to be true or false. I meant that the ultimate reality of statment B is predicated upon the TRUE OR FALSE value of A.

quote:I hope this helps to further clarify the issue for you

I sort of understand -- let''s call it a 0.7.