Information Technology Reference
In-Depth Information
If Bert does not know some relevant facts about Burger World, he should attribute some
kind of expected utility to them, in which case discovery that the Thai Palace was of
good quality might not immediately displace Burger World, and the question as to price
would still be important.
Beneath the surface of the dialogue, the pragmatic meaning of the utterances in the
context of persuasion is that Bert is asking a sequence of questions about whether at-
tributes that he values enough to be able to change his current preference are satisfied by
the proposed option and (in open persuasion) by his currently preferred option. Wilma's
role is to answer these questions. We suggest also that Bert should ask about criteria in
order of their importance to him. We now develop an algorithm based on this principle
and show in section 5 that this represents an optimal strategy. Thus following Grice's
maxims, and taking the pragmatics of the dialogue type seriously, has computational
benefits.
4
Protocol and Strategy
The persuasion dialogue, (W1-B3 in the example), once it has been initiated by the
persuader, is a series of statements and requests for information on the part of the per-
suadee. Either these will be a statement of the form
τ
1
j
=1
, or a question of the form
whether
τ
1
j
=1
. In either case, in the terms of [2], the persuadee wishes to open in-
quiry dialogues with
τ
1
j
and
τ
2
j
as topics (in open persuasion) or with
τ
2
j
as the only
topic (in partial persuasion).
This can be accomplished using a series of inquiry dialogues. Since that of [2] has
been shown to be sound and compete, it can be used to give Bert the best information
available, the knowledge derivable from the union of the KBs. We will therefore assume
the use of the protocol of [2] to exchange information. When should the persuasion di-
alogue terminate? If
O
1
is Bert's currently best option, and Wilma is trying to persuade
him of
O
2
, Bert should continue to seek information until the minimum utility of
O
1
is greater than the maximum utility of
O
2
, in which case Wilma's proposal can be re-
jected, or until minimum utility of
O
2
exceeds the maximum utility of
O
1
,inwhich
case her proposal can be accepted. This state will be approached by initiating inquiry
dialogues to verify as yet unverified features of the options. When
UT
i
=
UF
i
=
,
the dialogue must terminate, since the option with the highest current utility cannot be
displaced. Often, however, it will terminate with only a subset of the attributes verified:
in the example above it may terminate if good quality is true of one but not the other;
if true of both or neither it could terminate for Wilma if cheap is true of one but not the
other, and she will consider whether they are licenced only if the options are the same
in terms of quality and price.
∅
T
1
(
X
)
be the condition that the algorithm has
terminated with
O
1
preferred when the status of all the attributes associated with the
weights in
X
Definition 9.
Termination condition. Let
W
is known to the persuadee.
T
1
(
X
)
holds if and only if
⊆
τ
2
j
w
j
>
w
j
∈W\X
τ
1
j
w
j
−
w
j
. Similarly for
T
2
(
X
)
.
w
j
∈X
w
j
∈X
