UAS accredits personnel certification bodies on the basis of the ISO/IEC 17024 standard.Accreditation of a personnel certification body is the process of assessing and publicly recognizing the credibility, impartiality and technical competence of an organization's personnel certification services. Personnel certification bodies provide services for many professional and trade persons, such as auditors, welders and doctors. The role of certification bodies involves assessing the individuals' necessary competencies, and ensuring that these are appropriate to the work being performed.The major difference between this and a diploma is the certification involves ongoing supervision. A certificate therefore has a specific period of validity.