Thursday, 21 June 2007

25.4-5, Reasoning About Rational Agents

Notes taken from 'Reasoning About Rational Agents' (2000), by Michael Wooldridge

4, LORA Defined

(Syntax; Semantics; Derived Connectives; Some Properties of LORA)

5, Properties of Rational Agents

BDI Correspondence Theory

Pairwise Interactions between Beliefs, Desires and Intentions

(Int i X) => (Des i X): If an agent intends something, then it desires it. Intuitively, this schema makes sense for rational agents...

(Des i X) => (Int i X): If an agent desires something, then it intends it. In other words, an agent intends all its options... This formula does not appear to capture any interesting properties of agents.

(Bel i X) => (Des i X): This is a well-known, if not widely-admired property of agents known as realism ("accepting the inevitable"). For example, suppose I believe that the sun will definitely rise tomorrow. Then, one could argue, it makes no sense for me to desire that the sun will not rise... As a property of rational agents, realism seems too strong...

(Des i X) => (Bel i X): If an agent desires something, then it believes it. To give a concrete example, suppose I desire I am rich: should I then believe I am rich? Clearly not.

(Int i X) => (Bel i x): If an agent intends something, then it believes... Suppose I have an intention to write a book; does this imply I believe I will write it? One could argue that, in general, it is too strong a requirement for a rational agent... While I certainly believe it is possible that I will succeed in my attention to write the book, I do not believe it is inevitable that I will do so...

(Bel i X) => (Int i X): If an agent believes something, then it intends it. Again, this is a kind of realism property... Suppose that I believe that X is true: should I then adopt X as an intention? Clearly not. This would imply that I would choose and commit to everything that I believed was true. Intending something implies selecting it and committing resources to achieving it. It makes no sense to suggest committing resources to achieving something that is already true.

These formulae are a useful starting point for our analysis of the possible relationships that exist among the three components of an agent's mental state. However, it is clear that a finer-grained analysis of the relationships is likely to yield more intuitively reasonable results.

Varieties of Realism

(Int i X) => ¬(Des i ¬X)
(Des i X) => ¬(Int i ¬X)
These properties say that an agent's intentions are consistent with its desires, and conversely, its desires are consistent with its intentions... These schemas, which capture intention-desire consistency, appear to be reasonable properties to demand of rational agents in some, but not all circumstances... Under certain circumstances, it makes sense for an agent to reconsider its intentions - to deliberate over them, and possibly change focus. This implies entertaining options (desires) that are not necessarily consistent with its current intentions...

(Bel i X) => ¬(Des i ¬X)
(Des i X) => ¬(Bel i ¬X)
These schemas capture belief-desire consistency. As an example of the first, if I believe it is raining, there is no point in desiring it is not raining, since I will not be able to change what is already the case. As for the second, on first consideration, this schema seeems unreasonable. For example, I may desire to be rich while believing that I am not currently rich. But when we distinguish between present-directed and future-directed desires and beliefs, the property makes sense for rational agents...

Systems of BDI Logic

The Side-Effect Problem

The side-effect problem is illustrated by the following scenario: "Janine intends to visit the dentist in order to have a tooth pulled. She is aware that as a consequence of having a tooth pulled, she will suffer pain. Does Janine intend to suffer pain?"

... It is generally agreed that rational agents do not have to intend the consequences of their intentions. In other words, Janine can intend to have a tooth pulled, believing that this will cause pain, without intending to suffer pain.

No comments: