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During my postgraduate studies I researched logics for the planning of communication protocols, with a focus on their computational properties. By extending logics of knowledge with operators for quantifying over information change, we can express statements about whether a change in information can result a desired knowledge state. For example we express the statement that "there is a change in information that results in Alice knowing a secret, without Bob knowing that Alice knows the secret". Using model checking procedures we can determine whether the statement is true in a specific situation, using decision procedures we can determine whether the statement is true in general, and using synthesis procedures we can produce a specific example of a communication protocol that results in the desired change in information, in specific or general situations. This research lies in the areas of dynamic epistemic logic, epistemic protocol synthesis, and more generally, modal logics.

My main line of research is in refinement quantified modal logics, in the settings of multi-agent logics of knowledge and belief. In these settings there's a correspondence between refinements and action models, which are a very general model for communication in multi-agent logics of knowledge and belief. My thesis and publications show that refinement quantifiers correspond exactly to action model quantifiers, and I use this correspondence to show results for arbitrary action model logic.

More recently I've worked on a variant of arbitrary public announcement logic that restricts arbitrary public announcements to positive formulas, a variation of refinements called group refinements that are intended to generalise group announcements, and epistemic logics incorporating awareness of action models.

I completed my Ph.D. in May 2016, my thesis was titled *Logics for quantifying over information change*, supervised by Tim French and Rowan Davies.

Here is the abstract for the project:

Epistemic modal logic models the knowledge that a set of agents hold about the state of the world. The knowledge of agents may change in response to informative updates, events that communicate additional information about the world to the agents whilst leaving the world itself unchanged. We are interested in developing general techniques for determining how a set of agents with some initial knowledge can arrive at a certain state of knowledge through the execution of informative updates, perhaps subject to additional constraints. This could have applications in the development of communication protocols, or in the verification of secure systems. We extend epistemic modal logics with refinement quantifiers, operators in the logic that have the effect of quantifying over informative updates, allowing us to pose questions about the existence of informative updates that result in particular states of knowledge of the agents. We also consider the addition of refinement quantifiers to other modal logics, where refinements correspond to different kinds of “updates”; in logics for games, refinements may correspond to a player discarding possible moves from consideration, or in logics for topology, refinements may correspond to subspace projections. We investigate computational methods in the resulting refinement quantified modal logics, including methods to synthesise informative updates according to desired properties in refinement quantified epistemic modal logic.

2014

L. Bozzelli, H. van Ditmarsch, T. French, J. Hales, and S. Pinchinat.

*Refinement modal logic*.

Information and Computation (2014).

T. French, J. Hales, and E. Tay.

*A composable language for action models*.

Proceedings of the 10th conference “Advances in Modal Logic” (2014), College Publications, pp. 197-216.

2013

J. Hales.

*Arbitrary action model logic and action model synthesis*.

Proceedings of the 2013 28th Annual IEEE/ACM Symposium on Logic in Computer Science (2013), IEEE, pp. 253-262.

2012

J. Hales, T. French, and R. Davies

*Refinement quantified logics of knowledge and belief for multiple agents*.

Proceedings of the 9th conference “Advances in Modal Logic” (2012), College Publications, pp. 317-338.

2011

J. Hales, T. French, and R. Davies

*Refinement quantified logics of knowledge*.

Proceedings of the 7th Workshop on Methods for Modalities, Electronic Notes in Theoretical Computer Science 278 (2011), Elsevier, pp. 85-98.

You can also see my profile on Google Scholar.

2016

J. Hales

*Logics for quantifying over information change*.

Doctoral thesis (2016), The University of Western Australia.

Link: UWA Research Repository; GitHub.

2014

H. van Ditmarsch, T. French, and J. Hales

*Positive announcements*.

Proceedings of the 20th School of Computer Science & Software Engineering Research Conference (2014).

T. French, J. Hales, and E. Tay.

*A composable language for action models*.

ArXiv preprint, arXiv:1406.2103 (2014), extended version.

2011

J. Hales.

*Refinement Quantifiers for Logics of Belief and Knowledge*.

Honours thesis (2011), The University of Western Australia.

Link: GitHub.