Semantics impacts of distribution upon sequential code

• Reachability, additional dependence on the network (latency and through-put). The object may be OK, but the host is down or non-reachable.
• Non-determination: the state of the remote object may change, and is not the one in which it was left.
  • One cannot accept the raise in non-determination since it impairs availability (or scalability at constant availability, or efficiency...)
  • On the other hand, one cannot expect clients to monitor the environment
• Dead-locks: non-availability, either temporary, or intrinsic.

These alter the semantics of the service contract.

These changes spread along use chains: higher-level services are more affected!

Table of contents