 A frame is a collection \(\{\cD_{\alpha}\}_{\alpha}\) of nonempty domains (sets) \(\cD_{\alpha}\), one for each type symbol α, such that \(\cD_{{o}} = \{\sfT,\sfF\}\) (where \(\sfT\) represents truth and \(\sfF\) represents falsehood), and \(\cD_{\alpha \beta}\) is some collection of functions mapping \(\cD_{\beta}\) into \(\cD_{\alpha}\). The members of \(\cD_{\imath}\) are called individuals.