HT Tutorial Exercise 6 - Examine an impasse


Examining an impasse
Remove the hungry-thirsty rules by using excise --all, or re-start Soar, clearing out all rules that way. Load "ht-imps9.soar" this time. This file has more rules, but less high-level knowledge.

Run the model through the impasse that will appear, and compare your trace with Trace 5.

Do this at various watch levels. If you wish to know which rules will fire, use the debugger's Monitor matchSet window (or you can use the command matches to display the current match-set). To step at a finer grain through the program, use the e command.

To understand this impasse, you will have to see the preferences that are available for the operators in S1. You can see the preferences for operators with the previously covered preferences command (or use gui's Monitor Preferences window).


Checking production mapping
Try out   matches at several points when you are in the impasse, and find out why rules do and don't match (the problems should not be subtle).

Run ahead a decision cycle and try the command again, to see what's going on. This can be repeated if necessary.


Follow up questions
  1.  What caused the impasse?


  2. What rule would have prevented the impasse?



Follow up exercise
How can any set of attributes influence behaviour in the selection space? Write a new production(s) that modifies the selection based behaviour so that drinking is preferred if the beverage is 'real-ale'. Then, for your own amusement, modify the productions that create the drink operator to propose an operator that includes beverage Guinness.

Return to main page of: Introduction to Psychological Soar Tutorial
(or use the Back button to return to where you just were).
Program Listings
PST Soar Help