Competitive sports are governed by codified rules agreed upon by the participants. Violating these rules is considered to be unfair competition. Thus, sports provide artificial (not natural) competition; for example, competing for control of a ball, or defending territory on a playing field is not an innate biological factor in humans. Athletes in sports such as gymnastics and competitive diving compete against each other in order to come closest to a conceptual ideal of a perfect performance, which incorporates measurable criteria and standards which are translated into numerical ratings and scores by appointed judges.