Q5 — Rete Net: Lens Classification
Convex/Plane/Concave surfaces with radius comparisons — R2's Convex-Plane pair is the only listed full match, R3 wins specificity, R6 wins recency.
The Question
A Rete net classifies lenses by surface properties (Convex / Plane / Concave classes, radius of curvature, number of sides). Working memory:
101. (Concave ^itemNo K3 ^radius 70 ^sides 1)
102. (Concave ^itemNo K7 ^radius 10 ^sides 3)
103. (Convex ^itemNo K2 ^radius 60 ^sides 1)
104. (Convex ^itemNo K3 ^radius 50 ^sides 1)
105. (Convex ^itemNo K4 ^radius 20 ^sides 4)
106. (Plane ^itemNo K2 ^sides 1)
107. (Concave ^itemNo K1 ^radius 80 ^sides 2)
| # | Question | Official answer |
|---|---|---|
| 5.1 | Tuples in the conflict set (A: R1,105 · B: R2,103,106 · C: R4,102,103 · D: R5,102) | B |
| 5.2 | Specificity qualifies | B (R3,101,104) |
| 5.3 | Recency qualifies | D (R6,107) |
The Topic in 60 Seconds
Alpha nodes filter single WMEs; beta nodes join streams (on ^itemNo, plus the radius comparisons in B4/B5). Conflict set = all full tuples. Specificity = most conditions; Recency = newest max-timestamp.
Deep-dive: The Rete Algorithm.
The Rete Net (from the figure)
Rules: R1 = Convex sides-2 · R2 = same-itemNo surfaces with sides 1 (via B1) · R3 = same-itemNo pair with radius(a) smaller than radius(b) (via B4) · R4 = same with a larger than b (B5) · R5 = Plane + Concave sides-1 pair · R6 = Concave sides-2.
Step 1 — Locate every WME
| WME | Facts | Alpha path |
|---|---|---|
| 101 | Concave, K3, r70, sides 1 | A6 → A8 |
| 102 | Concave, K7, r10, sides 3 | A6 → A8 — fails every sides-1 test |
| 103 | Convex, K2, r60, sides 1 | A4 → A7 → A10/A11 |
| 104 | Convex, K3, r50, sides 1 | A4 → A7 → A10/A11 |
| 105 | Convex, K4, r20, sides 4 | A4 — fails A9 (sides 2) and the sides-1 nodes |
| 106 | Plane, K2, sides 1 | A5 → A12 |
| 107 | Concave, K1, r80, sides 2 | A6 → A15 ✓ (sides 2) |
Step 2 — Fire the joins
- R1 (Convex sides-2): no Convex WME has sides 2 — 105 has sides 4 → no match (kills option A).
- R2 via the Convex/Plane pair: 103 (Convex K2, sides 1) + 106 (Plane K2, sides 1) — same itemNo K2 ✓ → (R2, 103, 106) ✓
- R3 (radius comparison on the K3 pair): 101 (Concave K3, r70) + 104 (Convex K3, r50) — same itemNo K3, radii 50 < 70 satisfy "a smaller than b" ✓ → (R3, 101, 104) qualifies.
- R4: would need a larger than b on a sides-1 pair — 50 < 70 goes the wrong way; no other same-itemNo pair exists → no match.
- R5 (Plane + Concave sides-1, same itemNo): the only Plane WME (106, K2) has no Concave K2 partner; option D's lone (R5, 102) also fails because 102 has sides 3 → no match.
- R6 (Concave sides-2): 107 ✓ → (R6, 107).
Conflict set = {(R2, 103, 106), (R3, 101, 104), (R6, 107)} — of 5.1's options only B is a member ✓
5.2 — Specificity → B (R3, 101, 104)
Condition counts: R2 = class + sides + sides + itemNo-equality; R6 = class + sides; R3 = two class tests, two radius tests, two sides tests, plus the numeric comparison in B4 — the most conditions of any firing rule → its tuple (R3, 101, 104) wins → option B ✓
5.3 — Recency → D (R6, 107)
Max timestamp per candidate: (R2, 103, 106) → 106; (R3, 101, 104) → 104; (R6, 107) → 107. Newest WME wins → option D ✓
Tricks & Tips
Answers: 5.1 B · 5.2 B · 5.3 D