This chapter describes the active subsystem of PFL, a functional database
programming language (DBPL).  We discuss how PFL has been extended with
transactions and ECA-rules without compromising the confluence of expression
evaluation.  We describe the support for primitive and composite events, the
definition and semantics of ECA-rules, and the execution model.  To our
knowledge, this is the first time that an active subsystem has been added to
a functional DBPL.