Emergence of agreement. This dissertation combines insight from numerous different disciplines. Because of this, it is important to be aware of the significant differences in assumptions in various domains. We can distinguish between two types of models of agreement phenomena, intentional and unintentional models. In intentional models agreement is a designed end goal of the system. In unintentional models, agreement is a consequence of actions that are for a different purpose. As a concrete example, consider the distributed algorithm for agreement described in [Xxxxxxxx and Xxxxxxxxxxx, 2008b]. In this case, there is a multi-phase protocol involving an initial phase where agents learn the graph topology, then another phase to achieve consensus. These agents were designed with agreement in mind, and thus the model of agreement is intentional. In contrast, consider the agents described in [Steels, 2005a, Steels, 2003, Steels, 1998]. Once again, the goal is to understand the time it takes for the system to reach agreement. However, in this case individual agents are focused on just maximizing their success in communication with neighbors. Agreement is an emergent property of this simple interaction. Agreement is an unintentional consequence of their behavior, which is justified by appealing to its similarity to a human process. We view agents in [Steels, 2005a, Steels, 2003, Steels, 1998] as unintentional – agreement is a property that emerges because of other behavior. The questions to ask are whether the justification for the underlying behavior is valid. The results of work with unintentional models is often to indicate something interesting about the systems which are being modeled. In intentional models it is more plausible to have complex cognitive processing and multi-phase protocols (such as a phase for choosing a leader, then a phase to exchange information via the leader, as in the protocol to solve the distributed commit problem [Xxxxx, 1997]). Both intentional and unintentional systems involve the same core three processes of the Generalized Agreement Process but the plausibility of certain behaviors are different. The distinction between intentional and unintentional systems is exactly the underlying difference between sociological and technical systems. In this thesis we will view agreement as emergent, even though in some cases we are talking about intentional models.
