By all measures, the Web is enormous and growing at a staggering rate. This growth has made it both increasingly difficult and increasingly important for humans and programs to quickly and accurately access Web information and services. A semantic Web-in which meanings of terms are captured and exploited-can provide the foundation for convenient Web content access. The DARPA Agent Markup Language (DAML) program aims to provide a language and toolset that enables the Web to transform from a platform that focuses on presenting information to a platform that focuses on understanding and reasoning with information. In this article, we describe the DAML language; its goal is to capture term meanings, and thereby providing a Web ontology language. In addition to a brief history of the language's evolution, we introduce the ontology language DAML+OIL by way of examples and include an axiomatization of the language.