A breed standard in animal fancy and animal husbandry is a set of guidelines which is used to ensure that the animals produced by a breeder or breeding facility conform to the specifics of the breed. Breed standards are devised by breed associations or breed clubs, not by individuals, and are written to reflect the use or purpose of the species and breed of the animal. Breed standards help define the ideal animal of a breed and provide goals for breeders in improving stock. Breed standards are not scientific documents, and may vary from association to association, and from country to country, even for the same species and breed. There is no one format for breed standards across all species, and breed standards do change and are updated over time.