No.050 Software Contracts for Communication, Monitoring, and Security

Typed Racket has always relied heavily on Racket's
underlying contract system to maintain soundness when interacting with
untyped programs. But as Typed Racket has grown more sophisticated,
this has placed greater demands on the contract system.  In this talk,
I'll discuss several ways in which we've approached this question, and
focus on one challenge in particular: interacting with encapsulated
and mutable state.  Our solution, called chaperones, enables Typed
Racket to soundly exchange mutable data while not violating other
invariants that the system relies on.