HT Tutorial Exercise 2 - Run the model

Loading and running the hungry-thirsty code

Type the following into Soar (How to startup Soar if you forgot.):

source "ht.s7"

If you now init-soar and type d 2, Soar will run two decision cycles until the problem is solved and then halt. You can then examine the trace (what Soar prints out as it runs), to see what happened (this trace is also shown in Trace 3). Alternatively, you can type d 1, and examine each object as they are selected.

Several of the attributes in this model are traced (such as hungry and thirsty on the state), but there are several that are not. You can examine the problem space elements (and their substructures) in their entirety with p identifier. The identifier of each context element appears in the trace, such as S1, so an example usage would be p s1. This command can be recursively applied to sub-objects, or you can find out how to print them all at once by consulting help p.

If you lose track of how far you have run the model, you can type pgs to Print (the) Goal Stack. The current state is the state that is lowest down in the goal stack. The goal, or desired state, will normally be seen as an attribute of the current state.

Follow up questions

• How is this behaviour different from plain OPS5 or even GPS?

• What happens if you "excise ht*compare*eat*better*drink"?

• Try changing how the selection process works (use user-select).

• How would you extend the model from a single to double conjunct goal? (i.e., be not hungry and not thirsty?).