This paper proposes an adaptive participant's presumption protocol (Ap3) that can be used to atomically commit Internet transactions. Ap3 interoperates a one-phase commit protocol, namely, implicit-yes vote, and two-phase commit protocols, namely, presumed abort and presumed commit, in a dynamic fashion. Thus, it offers the performance advantage of the combined protocols, whenever possible, while still providing the wide applicability of two-phase commit protocols. This is achieved in spite ofthe incompatibilities between atomic commit protocols that lead to the general practice ofadopting a single atomic commit protocol in any distributed database system.