Certifications are most often awarded by industry organizations and are based on assessments of skills and knowledge. Licenses may be managed by local government agencies.
A certification can have an external ID for linking to off-chain data.
Certifications have an expiration date, which allows for requiring professionals to renew their certifications.
A certification will have defined requirements (courses). Each course is made up of a Module (subject)and Credits (hours). Once the professional has met all the requirements they will receive that certification.