Q5 — Rule Based Expert Systems

The mushroom net's FN twin: same four-tuple conflict set shape, specificity crowns the join-backed pair, recency hands it to option B.

The Question

A Rete Net classifying mushrooms (edible vs poisonous) with alpha stores A1–A16, beta joins B1–B3 and rules R1–R4. Note: attribute <> x is true when the attribute exists and differs from x.

#	Question	Official answer
6.1	Which rule-data tuples are in the conflict-set?	A, B, C, D
6.2	Specificity — which tuples qualify?	C, D
6.3	Recency — which tuple qualifies?	B

Source-data note

This FN variant's working-memory block was lost in transcription (the AN sibling carries the full nine-WME version). The machinery below is complete for this net; with the printed WMEs the keyed tuples regenerate mechanically.

Deep-dive: browse the Concepts section for Rule-Based Expert Systems / Rete.

Step 0 — Read the rule structure

Rule	Fed by	Condition pattern
R1	single alpha chain	Mushroom + odour NONE + sp-colour ≠ GREEN (single WME)
R2	B1	two-WME join on specimen $n$
R3	B2	two-WME join with a negated-test branch
R4	B3	cap-pair join (WHITE ⋈ RED/SMOOTH family)

The four-step procedure

1. File: each WME lands in one CLASS store, binds $n$ , survives at most one attribute filter per branch. Absent attributes FAIL comparisons — a WME without ^sp-colour never reaches a sp-colour <> GREEN node.

2. Join: every B-node intersects $n$ -sets:

$B_i:\ n(\text{left store}) \cap n(\text{right store})$

Each surviving $n$ emits one tuple per downstream rule.

3. Conflict set: the keyed answer A,B,C,D = exactly four surviving tuples — one per rule in this net, i.e., every rule found support and no join produced duplicates.

4. Resolve:

Specificity counts constant tests per rule. The join-backed tuples (each carrying 4–5 tests across two WMEs) dominate the single-WME chain → keyed winners C, D are the deepest-chain tuples; ties break by label order.
Recency compares sorted-descending timestamp lists, newest element first, longer list winning prefix ties. Keyed winner B is the tuple whose newest supporting WME carries the largest timestamp in WM — typically the last-inserted band of its combination.

Worked micro-example (illustrative)

WM: 301 Mushroom ^specimen M1 ^odour NONE ^sp-colour WHITE, 302 Stalk ^specimen S1 ^br-surface SCALY, 303 Stalk ^specimen S1 ^root BULBOUS, 304 Cap ^specimen C1 ^colour WHITE, 305 Cap ^specimen C1 ^surface SMOOTH ^colour RED:

Filing: 301 → odour-NONE chain → (R1, 301); scaly+bulbous both at $n{=}S1$ → B1 → (R2, 302, 303); white+red-smooth at $n{=}C1$ → B3 → (R4, 304?, 305) per the net's pairing.
Conflict set size 3–4 depending on the second cap store.
Specificity ranks join tuples first; recency compares [305,…] style lists — newest stamp wins.

Tricks & Tips

Answers: 6.1 A, B, C, D · 6.2 C, D · 6.3 B