Bart Verheij
Course in the post-graduate program
of the Computer Science Department
at the Universidad Nacional del Sur
in Bahia Blanca, Argentina
April - May, 1999
Questions
1. Give an attack relation with n stage extensions, for any natural number n.
2. I hardly spoke of defeat caused by specificity, which is a central ingredient of Simari and Loui's mathematical treatment of defeasible reasoning and of Simari, Chesñevar and García's Defeasible Logic Programming. Give an example of two arguments, one of which is defeated by the other because it is less specific than the other. Draw its reason/conclusion-structure (you will probably want to use subreasons) and give the corresponding defeater in CumulA. Is it of sentence-type, of step-type or of composite-type? Explain why CumulA's defeaters are not the right tool to distinguish specificity defeat from other types of defeat. Give your (motivated) opinion on whether I should have paid more attention to specificity defeat.
3. Give your (motivated) opinion on the accrual of reasons. Should it be included in a model of defeasible argumentation? Is it harmful to include it? (Don't forget to explain what you think the accrual of reasons is.) Include a discussion of Pollock's argument against the accrual of reasons. (You can find it in his book Cognitive carpentry (1995) and in his 1987 paper 'Defeasible reasoning' in Cognitive Science, Vol. 11, pp. 481-518.)
4. Consider arguments as reason/conclusion-structures, formed by the subordination and the coordination of argument steps (no subreasons). Assume that each pair of sentences (y
, j
) is assigned a 'connection value' s with 0 £
s £
1, that represents the strength of the argument step 'y
. Therefore j
'. Define the strength of arguments as follows:
Contact information
Bart Verheij
Department of Metajuridica
Universiteit Maastricht
P.O. Box 616
6200 MD Maastricht
The Netherlands
+31 43 3883048
b.verheij at ai dot rug dot nl
http://www.ai.rug.nl/~verheij/