clarification on b and d of qn 3 (the robot question).

["Subbarao Kambhampati" <rao@asu.edu>]

Several people asked for clarification as to how b and d differ. 

The idea is that in "b" you only consider the question from a pure graph-theoretic
perspective (e.g., purely in terms of directroute(x,y)). Here, we don't need to consider 
situation calculus at all. 

In "d" you are thinking in terms of actions and effects and specific plans (so you need to consider situation calculs).

Hope this helps. (People who are still confused might want to skip b and do the rest..)

Rao


=====the problem from homework
In this exercise, we will consider the problem of planning a route for

a robot to take from one city to another. The basic action taken by
the robot is Go(x,y) which takes it from city x to city y if there is
a direct route between the cities. DirectRoute(x,y) is true if and
only if there is a direct route from x to y; you can assume that all

such facts are already in the KB (see the map on page 63 of the text

book). The robot is in Arad and must reach Fagaras.

a. Write a suitable logical description of the initial situation of
the robot


b. Write a logical query whose solutions will provide possible paths
to the goal

c. Write a sentence describing the Go action

d. Write a suitable query whose answer can provide the plan for the
robot to go from Arad to Fagaras.


e. Use resolution refutation to answer the query and output the plan.

f. Suppose the Robot was wearing a redshirt and green pants when it
was in Arad. We want it to be wearing the same dress when it reaches

Fagaras. Explain how your answers to the parts a-e change.