On the minimal characterization of the rollback-dependency trackability property

Checkpoint and communication patterns that enforce rollback-dependency trackability (RDT) have only online trackable checkpoint dependencies and allow efficient solutions to the determination of consistent global checkpoints. Baldoni, Helary and Raynal (1998) have explored RDT at the message level, in which checkpoint dependencies are represented by zigzag paths. They have presented many characterizations of RDT and conjectured that a certain communication pattern characterizes the minimal set of zigzag paths that must be tested online by a checkpointing protocol in order to enforce RDT. The contributions of this work are: a proof that their conjecture is false; a minimal characterization of RDT; and introduction of an original approach to analyze RDT checkpointing protocols.