Certification is the means by which a person (or enterprise), as a result of training, education, external review and assessment, receives official approval of being able to competently complete a job or task. Certification can be a legal requirement or a measure undertaken voluntarily for professional advantage. Certification schemes which are mandatory by legislation have the advantage of providing a strong incentive for technicians and enterprises to comply. Certification does not refer to the state of legally being able to practice or work in a profession. That is normally achieved by a licensing. Usually, licences are administered by a governmental entity primarily for public protection purposes and professional associations administer certification schemes. Licencing and certification are similar in that they both require the demonstration of a certain level of knowledge or ability.