The chief points of Optimality Theory as presented in Prince and Smolensky [Prince, Alan and Smolensky, Paul, 1993, "Optimality Theory: Constraint Interaction in Generative Grammar", Rutgers University Center for Cognitive Science] are these. First, all constraints are universal. Second, constraints can be violated in well-formed sentences. A grammar is a ranking of the universal constraints which determines which constraint is satisfied in case of a conflict. The optimal form (that which best satisfies the constraints under the ranking in the grammar) is grammatical, all non-optimal candidates are ungrammatical. An optimal output form for a given input is selected from among the class of competitors in the following way: a form which, for every pairwise competition involving it, best satisfies the highest-ranking constraint on which the competitors conflict, is "optimal".
- Grimshaw (2004), a pag.384-385