Summary: Concurrent interaction games
1 A question and a challenge
Our starting point will be a question and a challenge posed by Tony Hoare
in [Hoare99]. The question:
Is game semantics inherently sequential?
and the challenge:
If this is not the case, then it would be nice to obtain a topdown
extensional characterization of sequentiality within a model that is
nonsequential. ...A full explanation of the concept of sequentiality
must surely give equal weight to the alternative.
As we will see, some recent work with PaulAndré Melliès [AM99] is directly
relevant to these issues.
2 Background: Why Games?
Firstly, though, we should provide some context for these questions, and why
they are of interest in the first place.
As Information Technology has progressed from batch processing through
multitasking operating systems to distributed systems and on to today's In
ternet, the focus has correspondingly shifted, from standalone programs to
systems, and from computation to interaction. The ``firstgeneration'' models