Artificial argument assistants for defeasible argumentation

1. Artificial argument assistants for defeasible argumentation Bart Verheij Presented by: Jacob Halvorson

2. Goal: Develop experimental argument assistance systems • Reasons • Administering and supervising the argument process • Keeping track of: • Issues raised • Assumptions made • Reasons for and against a conclusion • Evaluating the justification status of the statements • Checking for user error regarding rules of argument

3. Who would this help? • Single user: • Lawyer could use it in court • Analyze current arguments • Structure unpolished arguments • More than one user: • Argument mediation system • Keep track of diverging positions • Assist in the evaluation of opinions

4. Isn’t this like an Automated Reasoning System? • Automated Reasoning • Knowledge base • Complex reasoning is done for user • Argument Assistant • Assist user in reasoning (not replace user’s reasoning) • Complexities are less problematic since reasoning can be left to user

5. Argument Assistant and the Legal System • This paper focuses on using argument assistants to help with legal proceedings • Difficulties • Lack of a canonical theory of defeasible argumentation • New user interface must be designed • How to present arguments to the user • How users may perform argument moves • Legal • Legal rules are generally defeasible • Legal gap • Legal ambiguity

6. Dialectical Theory Construction Theory of the case, applicable law and the consequences are progressively developed

7. ARGUE! • Argument assistant based on the logical system CUMULA • CUMULA: Arguments (trees of reasons and conclusions) can be defeated • Defeat of arguments results from attack by other arguments (defeaters). • Types of defeat • Undefeated counterargument • Undefeated argument with conflicting conclusion • Problems • Not natural enough to represent real-life argumentation • On-screen drawing too complex

8. ARGUMED 2.0 • Major problems fixed from ARGUE! • Argumentation theory focused undercutting exceptions • Reasons that block the connection between a reason and a conclusion • Support by reasons and undercutting exceptions could be represented simultaneously. • User interface is template-based • Buttons to click which will bring up a given template • Evaluated by ten testers • Show unexplained examples and try to reproduce argumentation samples in the system • ARGUMED based on DEFLOG

9. ARGUMED based on DEFLOG • Mouse-sensitive argument screen • Add a statement box by double-clicking • Right mouse gives access to • Add support for statement • Attack against statement • Better argumentation theory • May attack any statement • Arrows between a reason and its (supported or attacked) conclusion are considered conditional statements

10. ARGUE! and ARGUMED based on DEFLOG in a case of inflicting grievous bodily harm • Precedent 1 • Victim has several broken ribs, but no complications • Precedent 2 • Victim has several broken ribs with complications *Intentional infliction of grievous bodily harm is punishable by 8 years in prison.

11. ARGUE! evaluation rules • A statement that is now set to justified or unjustified by the user, keeps its status. • A statement that now has justified support, is next justified. • A statement that now has no justified support and is attacked, is next unjustified. • A statement that now has no justified support and is not attacked, is next not evaluated.

12. ARGUE! results User can arrange statements at will White box = justified Gray box = not justified Dotted line & Dot = connection no longer justified • User can set status of statement • Justified • Unjustified • Not evaluated

13. ARGUE! Results (cont’d) Crossed out box = conclusion unjustified Limitations • Undercutting defeater can’t be challenged • If a statement is a reason for another can’t be challenged • Ex. Witness is unreliable

14. ARGUMED based on DEFLOG examples • Allows support and attack of any statement

15. ARGUMED based on DEFLOG evaluation rules • A statement is justified if and only if • It is an assumption, against which there is no defeating reason, or • It is an issue, for which there is a justifying reason. • A statement is defeated if and only if there is a defeating reason against it. • A reason is justifying if an only if the reason and the conditional underlying the corresponding supporting argument step are justified. • A reason is defeating if and only if the reason and the conditional underlying the corresponding attacking argument step are justified.

16. ARGUMED based on DEFLOG results • ! = assumptions • ? = issue • Dark bold = justified • Line through text = defeated • Light italic = unevaluated Result is not justified since inflicting grievous bodily harm is not justified and even defeated by testimony

17. ARGUMED based on DEFLOG resultsAdding testimonies of 10 pub visitors • By adding the testimonies of 10 pub visitors, the “grievous bodily harm” statement results in “unevaluated”

18. ARGUMED based on DEFLOG resultsAttacking a statement • Adding the rule that several broken ribs with complications count as grievous bodily harm results in the accuser doing the crime

19. ARGUMED based on DEFLOG screenshot

20. Conclusion • ARGUE! • Developed first • Based on CUMULA which isn’t sufficiently natural to apply to real-life argumentation • Can’t attack any statement • User interface isn’t intuitive • ARGUMED based on DEFLOG • Can attack any statement • User interface allows for use of mouse to edit argumentative data on the screen