is the one in which symbols and logic constitute the model. The symbolism used can be a language or a mathematical notation. A verbal or written description in English is an abstract model. A mathematical model is described in the "language" of mathematical symbols and is an abstract model. A simulation model is built in terms of [..]

is a “procedure by which an authoritative body gives formal recognition that a body or person is competent to carry out specific tasks.” [International Organization for Standardization]