IDP is a knowledge Base System (KB-system) for the FO(·) language. A Knowledge Base system is a system that supports multiple forms of inferences for he same Knowledge Base. FO(·) is an extension of first-order logic (FO) with types, aggregates, inductive definitions, bounded arithmetic, partial functions, etc. More information about FO(·), including an editorial by David Warren, can be found on the FO(·) language page. For a motivation of the Knowledge Base paradigm, see an application for interactive configuration. Using IDP, it is possible to model systems and problems, both from the real world as several artificial intelligence research problems. Solutions to these problems can then be found using one or more inference techniques. One class of real world problems that serves as a nice introduction to IDP is a scheduling problem.