Page 119 - DCAP310_INTRODUCTION_TO_ARTIFICIAL_INTELLIGENCE_AND_EXPERT_SYSTEMS

Unit 6: Formalized Symbolic Logics

tms-create-node (jtms datum assumptionp contradictoryp) creates a sentence node. The Notes
parameters are:

jtms, the jtms within which the sentence node is to be created
datum, the sentence
assumptionp, true if this is an assumption node; initially the assumption is retracted
contradictoryp, true if this is a contradictory node
Note that premise nodes are recognised because they are given a justification without any
premises.
enable-assumption (node), retract-assumption (node). These functions respectively enable
and retract an existing assumption node.
justify-node (informant conclusion-node list-of-premise-nodes), creates a justification
node. The parameters are:

The informant, that is who/what is entering this justification
The conclusion-node and list-of-premise-nodes that specify respectively the
conclusion and the premises of this justification.

Here is a simple dependency network:
contradiction
|
x
|
g o o h
| |
x x
/ \ / \
/ \ / \
o o o
A C E
This network is created:
(setq *jtms* (create-jtms “Forbus-deKleer example on page 181”))
The nodes A, C, E are created and enabled:
(setq assumption-a (tms-create-node *jtms* “A” :assumptionp t)
assumption-c (tms-create-node *jtms* “C” :assumptionp t)
assumption-e (tms-create-node *jtms* “E” :assumptionp t))
(enable-assumption assumption-a)
(enable-assumption assumption-c)
(enable-assumption assumption-e)
The node h is created and justified:
(setq node-h (tms-create-node *jtms* “h”))
(justify-node “R1” node-h (list assumption-c assumption-a))
;; R1 is the informant for this
;; justification
The node g is created, justified, and established as a contradiction:
(setq node-g (tms-create-node *jtms* “g”))
(justify-node “R2” node-g (list assumption-a assumption-c))
(setq contradiction (tms-create-node *jtms* ‘contra
:contradictoryp t))
(justify-node “R3” contradiction (list node-g))
This last command will recognise that a contradiction exists and will
invoke a contradiction handler that should state that the node
“contradiction” is a contradiction and that some of the assumptions
in {A, C} should be retracted.
Here should be a larger dependency network as used in a JTMS.

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