At the core of the AR is a set of twenty-four emotion categories sketched in table 1 and based on the original work of Ortony et al. [Ortony, Clore, & Collins1988]. Situations arise in an AR agent's world, and are appraised by matching these against more-or-less static frames (but which have dynamic procedural attachments) maintained by the agents. The dispositional way in which agents match the situations that have arisen gives rise to interpretations, represented as sets of variable bindings. Through a series of about twenty processing modules, these bindings are combined with states maintained internally by each agent, and eventually may, themselves, give rise to one or more emotion instances from the twenty-four categories. The processing in this appraisal stage accounts for agents' abilities to form, e.g., hypotheses about the ways in which other agents are presumed to appraise the world (necessary for fortunes-of-others emotions such as pity), matches against previous, and (presumed) future, world states (necessary for time-relevant emotions such as hope, and relief), and compound emotions such as anger (involving thwarted goals, caused by the perceived intentional act of an agent). Processing in this stage includes, among other concepts, representations for the antecedents of emotion intensity (with some subset of about twenty variables relevant to each emotion category), for agent's moods (non-dispositional, temporary, changes in the appraisal mechanism), for relationships between agents, for mixed and even conflicting emotions, and for heuristic classification of situation artifacts for abductive reasoning about the emotion states of others.
Once emotions arise, agents have temperaments which control the ways in which these emotions are manifested in their world. These temperaments are represented as about twenty theoretically-based channels of action specific to each emotion (but with overlap between related emotions), ranging from purely somatic responses (such as turning red) at one end of the spectrum, to highly intentional responses at the other end (such as activating a scheme for invoking a plan to get even [but note that any real planning is beyond the scope of this work]). The resulting, approximately 440, expression channels are implemented as a rete-like network, and terminal nodes are realized as situation-event frames, constructed partially from the original appraisal bindings (see above). A number of processing modules, such as those that choose compatible actions from competing expressions, and those that take into account the current states of both the world, and the agent, filter the path from emotion instance to emotion manifestation (e.g., one might shout in anger, or might deny that there is anything wrong, but would not do both at the same time).
Using these, and other, devices, sophisticated personalities can be constructed: the appraisal mechanism gives them a rich disposition for construing the world, and the expression component gives them a unique temperament for expressing themselves. Disposition is constructed by encoding the goals (desires), principles (beliefs about right and wrong), and preferences (attractions) of the individual agents, and temperament is constructed by activating certain expression channels allowing us to inspire them with qualities like impatience, talkativeness, shyness, and so forth. Moods are effected by changing the thresholds for the variable bindings in the match process, and by altering the activation of the expression channels. For details of these, and other issues, see [Elliott1992, Elliott1993, Elliott1994b, Marquis & Elliott1994, Elliott & Siegle1993, Elliott & Ortony1992, Elliott1994a, Elliott1994c]). For related approaches and discussion, see [Picard1995, Colby1981, Elliott1994b, Bates, A. Bryan Loyall, & Reilly1992, Frijda & Swagerman1987, Reeves1991, Sloman1987, Pfeifer & Nicholas1985, Scherer1993, Toda1982, Nass & Sundar1994, Nagao & Takeuchi1994, Simon1967].
Figure 1: Emotion types