A Formal Model of Hypertext

For the workshop on Hypertext Standardization, organized by the National Institute of Standards and Technology in 1990, Danny B. Lange developed an abstract (reference) model which is formally defined in the specification language VDM (the Vienna Development Method).

Lange's Basic Data model of Hypertext

The Lange's Basic Data model is developed through stepwise refinement. Initially the meaning of a hyperdocument is defined as a database that has active cross-references, allowing the user to have nonsequential access to a text, thereby making the reading process nonlinear. A hyperdocument, in its simplest form, can be modeled as a set of nodes and a collection of links, where the nodes are documents and the links are cross-references.

David Lange chose the Vienna Development Method (VDM) because it supports the top-down development of software systems specified in a notion suitable for formal verification.