Some forms of independence

• Classic notion - strict independence: goals do not share variables

  ..., p(X), q(X), ...
  X/a

• Non-strict independence:
  • (pure goals) only one goal ``touches'' each shared variable (+ aliasing restrictions)

    ..., p(X), q(X), ...
    p(a).
    q(Y).

  Very important in programs using incomplete structures!

• CLP independence: answers of first goal consistent with all resolvents of second goal.

  :- X > Y, Z > Y, p(X), q(Z), ...

• Determinacy is also a form of independence (e.g., Andorra, AKL).

• Independence can be applied dynamically and at finer grain levels (e.g., Local independence, DDAS model, AKL stability, etc.)