  The purpose of this note is to describe a unified approach to the fundamental
results in the spectral theory of boundary value problems, restricted to the
case of Dirac type operators. Even though many facts are known and well
presented in the literature (cf. the monograph of Booss-Wojciechowski), we
simplify and extend or sharpen most results by using systematically the simple
structure which Dirac type operators display near the boundary. Thus our
approach is basically functional analytic, and consequently we achieve results
which apply to more general situations than compact manifolds with boundary.
  The details of the material presented here will be published elsewhere.
