Robert Dale presents a detailed description of the development of algorithms for the generation of referring expressions, and of the underlying structures that motivate these algorithms, in a dynamic domain. He provides a number of novel results in both knowledge representation and natural language generation that should have straightforward applications in other domains. Dale describes EPICURE, a natural language generating system, and its capacity to create referring expressions in a domain embodying several interesting features: The entities in the domain consist of masses and sets as well as the more usual singular individuals; during the development of a discourse, the entities may take on new properties, existing entities may be destroyed, and new entities may be created; and the discourses within which the entities appear are hierarchically structured, allowing for the integration of discourse-structural constraints on the use of anaphoric expressions. EPICURE is designed to generate text from underlying plans. Dale uses cooking recipes as examples, showing how the system must determine what level of explanation is required and how the events in the plan must be modeled to ensure that the references generated are accurate.