(1) For XML documents, the linkage of the document itself to the rules that govern its structure, which might be defined by a Document Type Definition (DTD) or an XML schema.
(2) In enterprise beans, a relationship that exists between two container-managed persistence (CMP) entity beans. There are two types of association: one-to-one and one-to-many.
(3) The semantic relationship between two or more classifiers that specifies connections among their instances. See also association end, client.
(4) A visual representation of the members in a group that shows relationships or provides additional information about the members of a group.