  Agent Based Models are very popular in a number of different areas. For
example, they have been used in a range of domains ranging from modeling of
tumor growth, immune systems, molecules to models of social networks, crowds
and computer and mobile self-organizing networks. One reason for their success
is their intuitiveness and similarity to human cognition. However, with this
power of abstraction, in spite of being easily applicable to such a wide number
of domains, it is hard to validate agent-based models. In addition, building
valid and credible simulations is not just a challenging task but also a
crucial exercise to ensure that what we are modeling is, at some level of
abstraction, a model of our conceptual system; the system that we have in mind.
In this paper, we address this important area of validation of agent based
models by presenting a novel technique which has broad applicability and can be
applied to all kinds of agent-based models. We present a framework, where a
virtual overlay multi-agent system can be used to validate simulation models.
In addition, since agent-based models have been typically growing, in parallel,
in multiple domains, to cater for all of these, we present a new single
validation technique applicable to all agent based models. Our technique, which
allows for the validation of agent based simulations uses VOMAS: a Virtual
Overlay Multi-agent System. This overlay multi-agent system can comprise
various types of agents, which form an overlay on top of the agent based
simulation model that needs to be validated. Other than being able to watch and
log, each of these agents contains clearly defined constraints, which, if
violated, can be logged in real time. To demonstrate its effectiveness, we show
its broad applicability in a wide variety of simulation models ranging from
social sciences to computer networks in spatial and non-spatial conceptual
models.
