Specification

The Specification pattern allows the decision of "how" to select an Entity from the Entity itself - it is a predicate that determines if an object does or does not satisfy some criteria.

This allows separation of complex or cross entity logic from the entites themselves.

See also:

Blogged The Specification Pattern

Double Dispatch

domaindrivendesign.org definitions:

• Specification http://dddstepbystep.com/r.ashx?T