In this article a semantic framework is developed that provides a logical description of the functionality of an interactive reasoning process. The concept of functionality description defines the functionality of a reasoning process abstracted from specific inference relations or knowledge bases. Moreover, a domain description is formalized. A number of properties of a functionality description are identified and related to properties of the domain. It is established under which conditions a functionality can be implemented by an inference relation and a knowledge base. © 2002 Wiley Periodicals, Inc.