How is batch control implemented in DCS systems per ISA-88?

DCS batch control per ISA-88: physical model (enterprise, site, area, process cell, unit, equipment module, control module), procedural model (procedure, unit procedure, operation, phase), recipe management (master recipe, control recipe, formula, procedure), and execution engine (sequencer running phases, state machine). Implementation: define equipment phases (fill, heat, agitate, transfer), create recipe procedures (sequence of phases with parameters), configure equipment allocation (unit selection, exclusive use), implement exception handling (abnormal conditions, interlocks), and design operator interface (recipe selection, batch status, intervention). ISA-88 separation of recipe from equipment enables flexibility. Historians capture batch context for analysis.