---
layout: pattern
title: Specification
folder: specification
permalink: /patterns/specification/
categories: pattern_cat
tags: pattern_tag
---

**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

![alt text](./etc/specification.png "Specification")

**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)
