  We describe an effort to soundly use off-the-shelf incremental SAT solvers
within ACL2 by modeling the behavior of a SAT solver library as an abstract
stobj. The interface allows ACL2 programs to use incremental SAT solvers, and
the abstract stobj model allows us to reason about the behavior of an
incremental SAT library so as to show that algorithms implemented using it are
correct, as long as the library is bug-free.
