ACM Press, November 1989. HAM has no provisions for enabling an exchange of information with other applications. Sun's Link Service , A Protocol for Linking. ACM Press, November 1989. A data model is a set of logical objects used to provide an abstraction of a portion of the real world.
Data models are necessary to express an application s design.
However, it is important to differentiate a hypertext system from a hypertext application. The former is an environment that facilitates the creation of the latter. Sun's Link Service , A Protocol for Linking. ACM Press, November 1989.