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Tossing Another Coin

The plan in Figure 11 has two decisions with unambiguous decision-rules. There are four ways of achieving the goal in this plan, because there are two sources of uncertainty.

```Initial:       (HOLDING-COIN)

Step  1 (1): (TOSS-COIN)
(AND (NOT (HOLDING-COIN)) (ON-TABLE) (KNOW-IF (FLAT-COIN))
(KNOW-IF (HEADS-UP)) (KNOW-IF (TAILS-UP)) (KNOW-IF (ON-EDGE)))
0 -> (HOLDING-COIN)

Step  2 (2): (DECIDE TOSS1S)
(and (FLAT-COIN)
T                ) => [TOSS1S: H]
(and (ON-EDGE)
T                ) => [TOSS1S: E]
(and (FLAT-COIN)
(TAILS-UP)
T                ) => [TOSS1S: T]
1 -> (KNOW-IF (ON-EDGE))
1 -> (KNOW-IF (FLAT-COIN))
1 -> (KNOW-IF (TAILS-UP))

Step  3 (4): (TIP-COIN)                           YES: [TOSS1S: E]
NO : [TOSS1S: T H]
(AND (FLAT-COIN) (KNOW-IF (HEADS-UP)) (KNOW-IF (TAILS-UP)))
1 -> (ON-EDGE)                  NO : [TOSS1S: H T]

Step  4 (5): (DECIDE TIP4S)                       YES: [TOSS1S: E]
NO : [TOSS1S: T H]
(and (TAILS-UP)
T                ) => [TIP4S: T]
T                ) => [TIP4S: H]
3 -> (KNOW-IF (TAILS-UP))       NO : [TOSS1S: T H]
3 -> (KNOW-IF (HEADS-UP))       NO : [TOSS1S: T H]

Step  5 (3): (TURN-OVER)                          YES: [TOSS1S: T]
NO : [TOSS1S: E H]
1 -> (FLAT-COIN)                NO : [TOSS1S: H E]

1 -> (TAILS-UP)                 NO : [TOSS1S: H E]

Step  6 (6): (TURN-OVER)                          YES: [TOSS1S: E][TIP4S: T]
NO : [TOSS1S: T H][TIP4S: H]
3 -> (FLAT-COIN)                NO : [TOSS1S: T H]

3 -> (TAILS-UP)                 NO : [TOSS1S: T H][TIP4S: H]

GOAL                                 YES: [TOSS1S: E][TIP4S: T]
3 -> (FLAT-COIN)                NO : [TOSS1S: T H]
6 -> (HEADS-UP)                 NO : [TOSS1S: T H][TIP4S: H]

GOAL                                 YES: [TOSS1S: E][TIP4S: H]
3 -> (FLAT-COIN)                NO : [TOSS1S: T H]
3 -> (HEADS-UP)                 NO : [TOSS1S: H T][TIP4S: T]

GOAL                                 YES: [TOSS1S: T]
1 -> (FLAT-COIN)                NO : [TOSS1S: H E]
5 -> (HEADS-UP)                 NO : [TOSS1S: E H]

GOAL                                 YES: [TOSS1S: H]
1 -> (FLAT-COIN)                NO : [TOSS1S: T E]
1 -> (HEADS-UP)                 NO : [TOSS1S: T E]

Complete!
```

Next: Opening a Door Up: Cassandra's Plans Previous: Tossing a Coin

Louise Pryor <louisep@aisb.ed.ac.uk>;