4. Hypermedia Models

4.1. Hypertext Abstract Machine

Hypermedia is divided into: 1) User interface, 2) hypermedia application (client), 3) HAM Hypermedia "engine" (server) that retrieves link and node information from database and passes that to the hypermedia application, 4) database.

4.2 Dexter Hypertext Reference Model

Purpose of Dexter model is that it is standard hypertext terminology coupled with a formal model of the important abstractions commonly found in a wide range of hypertext systems. Dexter model is actually a formal specification of generic hypermedis system written in Z (Proceedings of the Hypertext Workshop, NIST Special publication 1990).

Run-time layer: presentation of the hypertext, user interaction, dynamics

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(Presentation specifications)

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Storage layer: database containing network of nodes and links

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(Anchoring)

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Within component layer: the contents/structure of nodes.

Components is Dexter model concept of nodes, frames, cards and links in other systems.