The following glossary presents some conceptual definitions for terms used in the topic map community. When element tag names are mentioned, they are the tag names used in the XTM 2000–2002 syntax.
(Synonym: resource.) An information resource that is retrievable by some systematic means, using one or more addresses expressed in one or more formal addressing schemes. An online copy of a document, or an addressable portion of that document, are examples of addressable information resources.
Every addressable information resource can be regarded as a subject of a topic. If it is, it is called an addressable subject or, synonymously, a subject-constituting resource or a resource constituting a subject.