Australian Silky Terriers
By the mid-1800's men who worked their dogs in a variety of ways formed themselves into breed associations which drew up the original Breed Standards based on the physical traits required for dog to do the job it was bred for. This shifted the focus from function to physical characteristics.
From Function to Physical
Lhasa Apso puppy
The Breed Standard is a word picture of a pure-breed dog as published by the dog controlling bodies or Kennel Clubs in each breed's country of development. So the Breed specialist clubs were formed specifically for the purpose of developing a Breed Standard for their particular breed, selecting those unique physical characteristics which define the different dog breeds we know today. Breed Standards remain the thread which holds together the fabric of the breeds.
Over the years these Breed Standards have been subject to continual revision by committees of breed specialists. For example some Breed Standards have revised heights and weights in line with modern feeding which results in better bone formation, more substance, etc. Other Breed Standards have changed to accommodate modern grooming techniques. But these revisions still fully encompass correct breed type in the opinion of the breed specialists of today.