Any dog that expends a high level of energy in its daily activities can be considered a performance dog. Some examples are obvious: law enforcement dogs, field trial dogs, hunting dogs, sled dogs, agility dogs, and racing dogs.
Other examples are less obvious, but more common. Show dogs must perform and require high levels of energy to be successful. Dogs that accompany their owners on long daily runs or on frequent backpacking trips are another example.
Another example, and of course one that we are very focused on in DockDogs is the Dock Jumping dog. Big Air and Extreme Vertical competitions along with weekly training in endurance, strength and conditioning all require high performance.
The key is energy. If a dog is asked to regularly perform tasks that require extra energy (calories), it can be classified as a performance dog.