Wendelin Reich (2004)
Reasoning About Other Agents: a Plea for Logic-Based Methods
Journal of Artificial Societies and Social Simulation
vol. 7, no. 4
To cite articles published in the Journal of Artificial Societies and Social Simulation, reference the above information and include paragraph numbers if necessary
Received: 28-Dec-2003 Accepted: 05-Mar-2004 Published: 31-Oct-2004
Agent 1: "(My price is) $500"
Agent 2: "(I offer) $300"
Agent 1: "(My price is) $350"
Agent 2: "(I offer) $300"
Agent 1: "(My price is) $300"
Agent 1: "(My price is) $500"
Agent 2: "(I offer) $300"
Agent 1: "(My price is) $450"
Agent 2: "(I offer) $320"
Agent 1: "(My price is) $320"
|Hypotheses for Transcript 1||Hypotheses for Transcript 2|
(1) Parametric input sensitivity. Values which the model does or does not process in the form of parameters, sensitize or desensitize it to variations in its application or execution context. The exact mathematical form of the parameters defines the shape, the range and the complexity these variations may take.
(2) Range and mathematical structure of output values. The internal logic of the model and the specific details of its implementation constrain the range of, and the possible or enforced mathematical relationships between, its output values. In principle, it is always possible to construct input-output models that are functionally equivalent (i.e., mapping identical input to identical output) yet based on different transformative mechanisms. The remaining four criteria provide guidance in the process of selecting between such models.
(3*) Degree of realism. The implementation details of the transformative mechanism defined by a model represent the model's ontology (its "worldview"). It is sometimes argued that, other things being equal, a tight isomorphism between the transformative mechanism and the modeled domain is preferable. In practice, two alternative techniques almost never fulfill the other-things-being-equal-clause; therefore, we consider this criterion too weak to warrant application in subsequent sections. Specifically, as some readers may expect that we will criticize non-logic-based representations of social meta-reasoning for their "lack of realism", we state beforehand that this is not the case. From a psychological point of view, such criticism would be debatable at any rate.
(3) Understandability. As an alternative to evaluating the degree of realism built into a model, it does seem reasonable to assess whether the transformative mechanism of the model is easily or at least generally understandable by the modeler. Whatever else "understanding" a model's transformative mechanism may mean, it is clear that it involves being able to explain in broad outline how variations in the modeled domain translate into variations in the output of the model. Thus, a model is only understandable if it allows us to establish a (possibly complex or far-fetched) isomorphism between model and modeled domain. This means that the criterion of understandability is actually a subjectivized form of the criterion of realism. However, in contrast to this latter criterion, understandability affects directly how suitable the model is for explaining empirical observations with reference to the modeled domain.
(4) Changeability. As mentioned, any model is arbitrarily changeable in a trivial sense because it is always possible to construct an alternative but functionally equivalent model. Nonetheless, two equivalent models may well diverge with respect to the ease with which the modeler can make smaller changes to the model's internal structure in order to better understand this structure, in order to experiment with the model's behavior, in order to correct the model or in order to adapt it to variations in (or new information about) the modeled domain. Some models may support certain types of changes whereas alternative models support other types - in short, changeability is not a property of the model as such but relative to the specific adaptation that needs to be carried out. Thus, for the comparisons that follow, we will keep in mind that in order to compare two models with respect to their changeability, one must have an idea about what changes are most likely to occur.
(5) Implementability and executability. In ABSS, we generally want to implement the model in an available programming language or modeling environment and run it through a series of simulations - both for demonstrating the correctness of the model and for experimenting with its behavior (Macy and Willer 2002: p. 149). Although modern personal computers are powerful enough, in practice, to fulfill virtually all the computational needs arising in ABSS, some formal representations are too complex to warrant tailor-made implementations of suitable software. Similarly, off-the-peg programs are usually not available for every technique or calculus. Therefore, available or easily implementable software is a pragmatic advantage that can be difficult to disregard when choosing among alternative techniques.
2 Any continuous function can be approximated with arbitrary precision by a multilayer perceptron with a single hidden layer; two hidden layers are sufficient to approximate any discontinuous function (Haykin 1999: p. 209).
3 Instead of providing links that may soon become invalid, we suggest that the interested reader use any of these names on one on the Internet's better search engines - it is likely that the first hit will be the right link.
4 We have used LeanTAP for developing software for ABSS and will be most happy to share our experiences with readers.
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