Abstract Mismanagement of abnormal operating conditions has a very costly, yet avoidable impact for the Chemical Process Industry. For abnormal situation management (ASM) is key to assess quickly the plant situation and develop a plan on-line either to restore normal operation or to bring the process to a safe state. This paper addresses the important issue of including a teleological (intentional) dimension in process modelling for ASM by explicitly relating process components to functions and goals that must be achieved. A formal modelling framework that resort to means (functions and components) and ends (a hierarchy of goals) to distinguish between normal and abnormal situations, to reason about goal achievement, to trace the causes of a unit malfunction and to plan a course of action is presented. The means-ends model (MEM) is expressed as logical axioms in a knowledge base using situations calculus. This formal representation of a MEM allows continuously assessing plant situations, doing queries about the state of goals and functions, and testing alternative course of actions for feasibility and performance.