Talk:Backward chaining

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I changed The example to reflect changes I made to Forward chaining. --CH

1. If Fritz croaks and eats flies - Then Fritz is a frog 2. If Fritz is a frog - Then Fritz is green

The conclusion in the 5th paragraph: Fritz croaks and eats flies, so must be green; Fritz is green, so must be a frog.

This is inconsistent with the rules of inference. Did you mean "Fritz croaks and eats flies, so must be a frog; Fritz is frog, so must be a green"? --DL

This example is just wrong - it is forward, not backward chaining.

Why is the backward chaining example the same as the forward chaining example if they are different?

This article isn't very clear.

134.225.254.250 08:32, 23 April 2007 (UTC)

Some of the Prolog material online contains academic discussion on this topic. Unless someone beats me to it, I'll try to look it up again for stub improvement. Hotfeba 19:00, 28 July 2007 (UTC)

I think it's pretty clear. And the example should be the same because the difference is not in the rules but in the inference algorithm using it. Goal-driven is backward (working from the conclusion back to the antecedent) and data-driven is forward (working from antecedent to conclusion). I only have an issue with the analogy used with "top-down" and "bottom-up" -- IMO data driven is bottom up (because you start with the nitty-gritty detail and end at an abstraction) and goal driven is top-down (begin with abstraction and work your way to the detail.) Think of language parsers as special examples of it: if you work the grammar rules from sentence down to parts and try to match words, you do top-down parsing, goal-driven. If you start with the words finding rules which match the sequence you see, then you do bottom-up parsing, data driven. My other concern is that the rules should not mention Fritz but a variable. I will change that. Gschadow 15:41, 29 September 2007 (UTC)

Merge

The article is about computer science terms. If anything, they should be merged to Expert system. WLU 22:07, 30 April 2007 (UTC)

Oppose the Merge

It's a close one. I'm usually for merging, it seems like everyone wants to create a Wikipedia article but far fewer want to make them good. Sorry, I'm editorializing. Anyway, I actually came to this article thinking perhaps it should be merged. I just finished what was essentially a complete rewrite of the article on Expert systems. But as I look at this article it looks pretty good (surprisingly so actually a lot of the AI articles were not so great) and goes into more detail than I did or want to in the articles on Expert systems, knowledge-based systems, etc. So I recommend we keep it. RedDog (talk) 23:48, 4 December 2013 (UTC)

fritz may be a canary

The part of the explanation of the example where it is concluded that Fritz is a frog mentions "and not a canary". I'm pretty sure that we can't actually prove Fritz isn't a canary. We, as humans, intuitively know that something cannot be both a canary and a frog, but there is no rule to that effect in the knowledge base, thus the algorithm cannot conclude it. I think that phrase should be deleted. I'm not going to do it myself because I'm not 100% positive I'm right... 71.88.110.253 (talk) 20:44, 18 May 2008 (UTC)

I'm not 100% certain either but I think you are wrong. I think I know what you are referring to, it's a variant of the Frame problem and I think if we were talking about First Order Logic assertions or a theorem prover you would be correct. However, inference engines are not theorem provers, they are less powerful (there are deductions a theorem prover can make that an inference engine can't) but as a result they are a lot faster and more certain to complete. I think in this instance we would use the close world assumption that if we don't know X is true we assume it's false. Although come to think about it if I'm right about that it really is irrelevant that Joe is a frog. Still think it makes sense to keep but willing to be convinced otherwise. RedDog (talk) 23:56, 4 December 2013 (UTC)

Game Theory and Backward Chaining?

I've taken an overview class on Game Theory and I've used many expert system shells but I don't ever recall hearing anyone say that what you do by working backward in game theory is "backward chaining". I do see the point though, I actually remember when I was taking the Game Theory class and the professor was talking about it I thought "oh its analogous to backward chaining in an inference engine" but I don't recall ever seeing that mentioned in a book or article on either topic and if not I think we should remove it. I notice there are some refs here I need to check out perhaps they support it. RedDog (talk) 23:39, 4 December 2013 (UTC)

So I don't have the Russel and Norvig book but I did find the Computational Graphs book on Google books. There seemed like there might be a section of that book that talked about game theory but I couldn't tell because those pages were ones that Google didn't include. So I'm going to leave the statement as is for now. RedDog (talk) 00:01, 5 December 2013 (UTC)

Primates?

In the intro it says "but it [backward chaining] has also been observed in primates". There are no references for that and I doubt that the two existing references talk about primates, they are both computer science books. I think it's just takes us too far afield for no reason to leave that statement in and will delete it. RedDog (talk) 00:10, 5 December 2013 (UTC)

Assessment comment

The comment(s) below were originally left at Talk:Backward chaining/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

== Rated as logic2 stub == Also part of computer science project. See talk on problems with article example; citing source of it could help. Curing dead link and adding refs will also help. Also see talk on merge proposal. Hotfeba 18:51, 28 July 2007 (UTC)

Last edited at 18:51, 28 July 2007 (UTC). Substituted at 19:47, 1 May 2016 (UTC)