Intent: Specification pattern separates the statement of how to match a candidate, from the candidate object that it is matched against. As well as its usefulness in selection, it is also valuable for validation and for building to order

Applicability: Use the Specification pattern when

• you need to select a subset of objects based on some criteria, and to refresh the selection at various times
• you need to check that only suitable objects are used for a certain role (validation)

Credits:

• Martin Fowler - Specifications