As in most mediating systems3, in DiaLaw both roles in the dialog game are performed by humans. Although it is already instructive for law students if their mutual argumentation is monitored by a system, a goal to strive for is a computer in its role as opponent in the debate.4 The examples show interaction between humans, but probably in the future one of the human-players will be replaced by a computer-player. For the sake of readability the sample dialogs are informal.
Bert and Ernie, well-aware of damages that can be caused by driving into a 'bussluis', are discussing who should be held responsible for damages.
Ernie: I accept the municipality has to compensate 50% of the damages
For the computer to be helpful as a coach and teacher, a specific domain has to be chosen, for instance that of tort. Another way to restrict the subject of the dialog is to offer students a case description, and a list of statements from which they can select their favourite.
In the above dialog, several argumentation skills are trained. While explaining and elaborating on the subsequent moves of the dialog, it is indicated which specific skill is trained.
Although the Court of Justice decided differently, Bert chooses a reasonable first statement. He claims that the municipality has to compensate for only half of the damages. In the second move Ernie questions this statement. Questions are a powerful tool to use in education, since Bert now has the duty to defend his statement. Therefore, he is forced to make explicit the reasons why his statement holds. The first reason he claims is that the Municipality committed a tort. Ernie accepts this reason, not surprisingly, because it is a good reason. If someone questions the existence of a duty to compensate, a first step is to indicate the ground on which the duty is based. In the current case the fact that the Municipality committed a tort is the correct ground. If Ernie had been a computer-player, he could have asked for the reasons why the Municipality committed tort.
The next statement claimed by Bert is also a good one. He indicates explicitly that there exists an obligation to compensate. Ernie also accepts this statement, but still is not convinced about the correctness of the first claimed statement. After claiming the necessary preliminary statements, in the seventh move Bert claims a statement essential for the position he defends. Although Ernie could have questioned this statement in order to hear Bert's reasons, he follows another strategy.
The eighth move is an interesting point in the dialog. In that move Ernie takes over the initiative. He denies that the cab-driver was guilty for 50%. As long as a player just questions and agrees, the opponent holds the initiative. A way to grab the initiative and become the proponent of a statement is by denying. Ernie has become the proponent of the statement that the cab-driver is not guilty for 50%. Bert questions the denial, because he wants to know why Ernie thinks that his 50% is not appropriate. Ernie mentions the driving in a one way street in the wrong direction, and that without this violation there would not have been damage. To this point Bert agrees. He denies, however, that the violation was the only cause of the damage. As a reason backing his denial, he claims that the municipality is responsible for the damages too, because they acted negligent. This gives Ernie the insight that both the cab-driver and the municipality are to blame for the damages, and he accepts the first claimed statement of the game. Obviously, Bert and Ernie decided from a legal point of view better than the Court did. Only because the procedure already lasted so long the cab-driver did not appeal again. Experts in this field (e.g., the Dutch tort specialist professor Van Maanen) are sure the Supreme Court would have set aside the decision of the Court. In the working out of the example in the system CumulA, the result of the argumentation is different. In that discussion, the decision by the court is used as an authoritative argument. Since there are no points left open for discussion, the dialog ends.
In sum, the students were confronted with the following argumentation skills:
claiming (defensible) statements;
claiming reasons that justify questioned statements;
taking over the initiative in the dialog by denying.
The mentioned skills are important for any lawyer. For instance, these basic skills are used in legal practice frequently. First, positions are taken. In case the claims of the opponent are reasonable they can be accepted. However, probably not all claims of the other party are accepted, but some will be questioned, others will be denied. In the former case the opponent has to provide reasons for his claims, in the latter case initiative is taken over. Finally, convincing reasons justifying ones position can be based on law books or court decisions.
DiaLaw has been implemented in Prolog as a prototype. While consulting the following screen-dump, one should be well-aware that for use in an educational setting the user-friendliness is for now far too low. One of the necessary improvements is that the players should be offered a list of natural language sentences to choose from.