Jeff MacSwan has posited a "constraint-free approach" to analyzing code-switching. This approach views explicit reference to code-switching in grammatical analysis as tautological, and seeks to explain specific instances of grammaticality in terms of the unique contributions of the grammatical properties of the languages involved. MacSwan characterizes the approach with the refrain, "Nothing constrains code-switching apart from the requirements of the mixed grammars." The approach focuses on the repudiation of any rule or principle which explicitly refers to code-switching itself. This approach does not recognize or accept terms such as "matrix language", "embedded language", or "language frame", which are typical in constraint-based approaches such as the MLF Model.