We study two alternative bases for Belnap's four-valued logic and provide complete equational axiomatizations for them. One is called conditional composition logic. It has a single, ternary if-then-else connective with a sequential, operational reading, and four constants for the truth values. The other logic is called guard logic. The main motivation for this logic lies in its technical properties. It admits a useful type of canonical form (term representation), and a relatively simple strategy for equational reasoning.
['Alban Ponse', 'Mark B. van der Zwaag']
Belnap's logic and conditional composition