Propagator: A Family of Patterns

By: P. Feiler, W. Tichy
Published: Proc. TOOLS-23, July 28 - Aug. 1, 1997
Category: Propagation

Summary: Consistent update of objects in a dependency network.

• These patterns are similar to Observer [Gamma+95] or Publisher-Subscriber [Buschmann+96], which follow a depth-first propagation. These patterns, however, operate in a dependency network that may be an acyclic or a cyclic graph and may implement different update strategies.

Url: http://www.sei.cmu.edu/publications/articles/propagator.html

Pattern: Strict Propagator

Define a network of objects so that when one object changes state, all directly and indirectly dependent objects are updated immediately.

Pattern: Strict Propagator with Failure

Define a network of objects so that when one object changes state, dependent objects are updated or (in case of failure) marked as invalid.

• This pattern extends Strict Propagator with a valid marker.

Pattern: Lazy Propagator

Define a network of objects so that when one object changes state, other objects can determine whether they are affected by the changes and can bring themselves up to date.

Pattern: Adaptive Propagator

Define a network of objects so that when one object changes state, dependent objects are updated in a flexible manner. When an object changes, a forward propagation phase marks affected objects as invalid but does not actually update them.