 We now define models and frames. A model for hybrid logic is a triple \((W, R, V)\) where \(W\) is a non-empty set, \(R\) is a binary relation on \(W\), and \(V\) is a function that assigns an element of the set \(\{0,1\}\) to each pair consisting of an element of \(W\) and an ordinary propositional symbol. The pair \((W, R)\) is called a frame. Thus, models and frames are the same as in ordinary modal logic. The elements of \(W\) are called worlds and the relation \(R\) is called the accessibility relation. The model \((W, R, V)\) is said to be based on the frame \((W, R)\).