Exercise 2.1 Section 2.3 (page 50) argued that it was impossible to build a representation of a world that is independent of what the agent will do with it. This exercise lets you evaluate this argument.

Choose a particular world, for example, what is on some part of your desk at the current time.

i) Get someone to list all of the things that exist in this world (or try it yourself as a thought experiment).

ii) Try to think of twenty things that they missed. Make these as different from each other as possible. For example, the ball at the tip of the rightmost ballpoint pen on the desk, or the spring in the stapler, or the third word on page 66 of a particular book on the desk.

iii) Try to find a thing that cannot be described using natural language.

iv) Choose a particular task, such as making the desk tidy, and try to write down all of the things in the world at a level of description that is relevant to this task.

Based on this exercise, discuss the following statements:

(a) What exists in a world is a property of the observer.

(b) We need ways to refer to individuals other than expecting each individual to have a separate name.

(c) What individuals exist is a property of the task as well as of the world.

(d) To describe the individuals in a domain, you need what is essentially a dictionary of a huge number of words and ways to combine them to describe individuals, and this should be able to be done independently of any particular domain.