Our contributions O lin. progress Pe 0 Cctxt Ap P∈{PF/PD New prog. properties for obj. with partial methods Abstractions to establish contextual refinements (CR) Equivalence result(Abstraction Theorem)Our contributions • New prog. properties for obj. with partial methods • Abstractions to establish contextual refinements (CR) • Equivalence result (Abstraction Theorem) O lin. + progress P  O ctxt AP P  {PSF/PDF}