Susan Older 

Degrees held: B.S. in Computer Science, Washington University, 1989 

Year entered CMU: 1990 

Advisor: Stephen Brookes 

Research interests: denotational semantics for programming languages,
parallel programming languages, communicating processes, full abstraction,
fairness, temporal logic  

As a student in the Pure and Applied Logic program, my primary research
interests lie in the development of mathematical semantics for programming
languages and their use in proving properties about programs.  In
particular, I am interested in developing semantics which permit
reasoning about parallel programs at precisely the right level of
abstraction.  A semantics is fully abstract with respect to a given
behavior iff the semantics gives two terms the same meaning exactly when
they exhibit the same behavior in all program contexts.  In essence, a
fully abstract semantics makes exactly the distinctions necessary to
support reasoning about the desired behavioral properties.

In analyzing parallel programs, it is common to want to reason about
properties with respect to certain fairness assumptions.  Intuitively, a
computation of a parallel program is considered fair if every component
process that is enabled sufficiently often makes progress sufficiently often.
The definition of ``sufficiently often'' can vary, allowing several
different interesting notions of fairness.  My current research involves
finding a family of fully abstract denotational models for a language of
communicating processes (based on Hoare's CSP) which properly
captures various fairness assumptions and accounts for several related
notions of behavior.  The notions of behavior investigated so far
correspond closely with linear temporal logic.  Consequently,
full abstraction guarantees that the semantics equates two programs iff
they satisfy exactly the same linear temporal logic formulas.