  Abstraction-Carrying Code (ACC) has recently been proposed as a framework for
proof-carrying code (PCC) in which the code supplier provides a program
together with an abstraction (or abstract model of the program) whose validity
entails compliance with a predefined safety policy. The abstraction thus plays
the role of safety certificate and its generation (and validation) is carried
out automatically by a fixed-point analyzer. Existing approaches for PCC are
developed under the assumption that the consumer reads and validates the entire
program w.r.t. the full certificate at once, in a non incremental way. In this
abstract, we overview the main issues on incremental ACC. In particular, in the
context of logic programming, we discuss both the generation of incremental
certificates and the design of an incremental checking algorithm for untrusted
updates of a (trusted) program, i.e., when a producer provides a modified
version of a previously validated program. By update, we refer to any arbitrary
change on a program, i.e., the extension of the program with new predicates,
the deletion of existing predicates and the replacement of existing predicates
by new versions for them. We also discuss how each kind of update affects the
incremental extension in terms of accuracy and correctness.
