Rather than continue to hijack the Uncas thread, here's one you can use to discuss the subject.
Dogs can be trained to do a variety of jobs, from sniffing out dead bodies (cadaver dogs) to anticipating various forms of seizure; from providing unconditional love for the unloved to being the eyes/ears of the blind/deaf.
The people who train them for these tasks range from unpaid volunteers to highly paid professionals. The work for themselves, and for large organizations, both profit and non-profit in nature.
The organizations doing the training set their own rules for certification and re-certification, and their customers choose accordingly.
The dogs performing these duties carry a number of initial characterizations after their registered names, indicating their status with the various certifying organizations:
TDI = Therapy Dog International
TT = Temperament Tested (American Temperament Testing Society)
CGC = Canine Good Citizen
Any more questions?