 The interpretations of predicate symbols are conditions. They are subsets of the diagonal \(\{\langle \alpha , \alpha \rangle \mid \alpha \in \textsf{ASSIGN}\}\) (which is the meaning of \(\top)\). Subsets of the diagonal are tests: they modify nothing and simply pass on what is OK (satisfies the condition) and throw away what is not. The mapping \(\textsf{diag}\) that sends a set \(F\) of assignments to a condition \(\{\langle \alpha , \alpha \rangle \mid \alpha \in F\}\) is the link between the classical static and the dynamic world. For example, the relational composition of \(\textsf{diag}(F)\) and \(\textsf{diag}(G)\) is \(\textsf{diag}(F\cap G)\).