>     Title: Languages with interaction and symmetry
>     Speaker: Chung-chieh Shan <ccshan@post.harvard.edu>,
>     Harvard University
>     Wednesday 1/26, 11am, Core A
>
>     The interaction in a program between a subexpression and its
>     context, and the interaction in a distributed system between a
>     component and its environment, often exhibit symmetries analogous to
>     those in logic, linguistics, and geometry.  I report on two projects
>     to take advantage of these symmetries in the design and study of
>     programming languages.
>
>     First, I describe a computational interpretation of classical S4
>     modal logic.  "Can you both make it on Tuesday at noon?", said
>     Alice to Bob and Carol, trying to schedule a joint meeting among
>     the three of them.  Her question expresses a shared plan, which can
>     be formalized as a proof that, if Bob and Carol each know a boolean
>     value, then so can Alice.  To execute this multiagent plan is to
>     reduce this modal proof, which is to run this distributed program.
>
>     Second, I introduce a graphical notation for programs in the lambda
>     calculus with first-class continuations.  This notation unifies
>     many evaluation strategies and manifests the dualities among
>     them.  For example, the familiar "let" construct is dual to the
>     unfamiliar "shift" construct; the latter is useful for programming
>     Web interactions and can now be understood in terms of the former.
>
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