Production System example

1. if u, y --> m*
2. if z --> n*
3. if z, v --> k*
4. if a, b --> p
5. if c --> r
6. if d, e --> s
7. if f, g --> u
8. if h, q --> y
9. if p, (r or s) --> v
10. if u, v --> z
11. if d, e, g --> s, t
12. if a, b, f --> p, q

* -- a final conclusion, once we reach a conclusion, we can stop searching


We know a, b, c, f, g, h

Using a "first match" conflict resolution strategy:

Rule 4 matches, working memory now a, b, c, f, g, h, p
Rule 5 matches, working memory now a, b, c, f, g, h, p, r
Rule 7 matches, working memory now a, b, c, f, g, h, p, r, u
Rule 9 matches, working memory now a, b, c, f, g, h, p, r, u, v
Rule 10 matches, working memory now a, b, c, f, g, h, p, r, u, v, z
Rule 2 matches, working memory now a, b, c, f, g, h, p, r, u, v, z, n*

Done.

Using a strategy of selecting a more specific rule (has more conditions on the LHS):

Rule 12 matches, working memory now a, b, c, f, g, h, p, q
Rule 4 matches, no changes
Rule 7 matches, working memory now a, b, c, f, g, h, p, q, u
Rule 8 matches, working memory now a, b, c, f, g, h, p, q, u, y
Rule 1 matches, working memory now a, b, c, f, g, h, p, q, u, y, m*

Done.

Notice how we drew a different conclusion.  Lets revise the rules with salience values
and use salience for our conflict resolution strategy.

1. if u, y --> m* (.8)
2. if z --> n* (.7)
3. if z, v --> k* (.9)
4. if a, b --> p (.4)
5. if c --> r (.6)
6. if d, e --> s (.8)
7. if f, g --> u (.7)
8. if h, q --> y (.5)
9. if p, (r or s) --> v (.6)
10. if u, v --> z (.6)
11. if d, e, g --> s, t (.8)
12. if a, b, f --> p, q (.6)

On a tie, we will use "first rule":
We know a, b, c, f, g, h

Rule 7 matches, working memory now a, b, c, f, g, h, u
Rule 5 matches, working memory now a, b, c, f, g, h, r, u
Rule 12 matches, working memory now a, b, c, f, g, h, p, q, r, u
Rule 9 matches, working memory now a, b, c, f, g, h, p, q, r, u, v
Rule 10 matches, working memory now a, b, c, f, g, h, p, q, r, u, v, z
Rule 3 matches, working memory now a, b, c, f, g, h, p, q, r, u, v, z, k*

Done.

Notice how we drew three different conclusions using three approaches!