Epistemic Dynamics and Protocol Information
Tomohiro Hoshi

Abstract:
Mathematical representation of knowledge and belief has become a topic
of increasing interest.
An individual knows or believes certain things based on the
information she has.  What type of mathematical models can we use for
precise representations of her information, knowledge or beliefs?
When an individual's environment involves other individuals, she may
know what others know, and such knowledge depends on the knowledge
that others have. How can we represent the relations between her
knowledge and the knowledge of others?  Finally, an individual may
obtain new information during the course of her activities by
observing facts in nature, interacting with other individuals, making
inferences from what she previously knows, and so on. How can we
capture these informational changes in her knowledge?
Investigations of these questions have been addressed under the
umbrella term, `intelligent interaction', and they have been studied
in various fields.

There are two important aspects in describing intelligent
interaction. One is how agents' epistemic states change over relevant
informational events.  Different informational events change agents'
information differently and the way that informational events change
agents' information can be quite subtle.  Therefore, it is crucial to
get a good grasp on informational events and their informational
effects.
I call this aspect epistemic dynamics.
The other is what informational events can take place in the course of
agents' interaction. Both the information that agents have and the way
that the information changes depend not only on what informational
event happens but also on what kind of process agents' interaction
involves. Informational events that can happen reflect what the
process is and, as such, are important to be captured. I call the kind
of information protocol information.
The dissertation will investigate intelligent interaction from the
perspectives of epistemic dynamics and protocol information.  The
first objectives of the dissertation is to develop a formal framework
that represents the two perspectives.
The formal framework is developed by merging the two major systems in
the literature, Dynamic Epistemic Logic and Epistemic Temporal Logic.
The second objective of the dissertation is to illustrate how our new
framework can throw new light on existing philosophical problems. In
particular, we will study The Knowability Paradox and Epistemic
Closure Principle by using our formal framework.


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