Obligationes: Making an interactive website around a medieval game. Irma Cornelisse, Patrick Mast, Ricus Smid, Djura Smits Abstract: This report will describe what we did to implement the game obligationes and to get it on the web. Before we can describe this, it has to be explained what the game obligationes actually is. What is obligationes? Obligationes (or "obligations") is a formal disputation form that was widespread in medieval Europe. The earliest writings on obligations date from the beginning of the thirteenth century, but the theoretical roots can probably be found much earlier, assumably in Aristotle's "Topics". Obligationes can be viewed as a game between two players, the opponent (opponens) and the respondent (respondens). The opponent puts forward some hypothesis and the respondent decides whether he denies or admits the hypothesis. In the first case the game doesn't start, in the latter case the game is on its way. The opponent puts forward questions (propositions) that may or may not relate directly to the hypothesis. The respondent answers these questions with 'I concede', ' I deny' or 'I doubt it'. This is where the name of the game comes in: both players are obliged to follow a very strict set of rules that determine how a question should be answered according to both the hypothesis, the propositions already put forward and the real world. When the respondent follows these rules closely, he or she can maintain a consistent 'world' that follows logically from the original hypothesis. The goal for the opponent is to trick the respondent in 'responding badly' within the game time that the players agreed upon. When the game time is up or when the respondent has responded badly, the opponent ends the game by saying "cedat tempus". One interesting aspect of this logical game is that, while it is clear that obligationes were widespread and heavily discussed from the thirteenth century on, the actual purpose of the game remains unclear. There are many versions of the game, but we will work on two versions: positio and dubitatio. In positio, the first fact (the hypothesis) has to be held true through the game. In dubitatio, the first fact has to be held in doubt through the game. Our goal Our goal is to implement positio and dubitatio, so that a player can act as the respondent, and the computer plays the opponent. This implementation, along with extra information about the game, has to be accessible via a website. Furthermore, other students should be able to implement their own versions of the different games and add it to the website.