 Furthermore, the "opaque ascription" (denoted by codice_25) states that any type components whose definitions are not provided in the signature ("i.e.," codice_21) should be treated as abstract, meaning that the definition of a queue as a pair of lists is not visible outside the module.The body of the structure provides bindings for all of the components listed in the signature.To use a structure, one can access its type and value members using "dot notation".