Dialogues between agents often build patterns where certain message sequences are expected and other messages are expected to follow. Such dialogues may only arise spontaneously in societies of rather complex agents. This facilitates the description of even rather complex interaction structures. They provide a graphical means of describing message sequences that is easily and intuitively comprehensible. As UML is widespread as a collection of methods in object-oriented software engineering, many people are familiar with it.
Sequence diagrams show the order of messages agents exchange in a time limited situation.
They emphasise the chronological course of communicative actions. 2.6 Modelling agents is supported by a generic agent model. The structure is modular, so several different types of agents can be assembled, from simple agents interacting by reactive patterns of behaviour to social agents provided with complex planning and decision capabilities. In principle, there is no restriction against using other kind of agents. The second layer abstracts from the quite technical and low-level message level.