A Vision for Open Hypermedia Systems Nürnberg and Leggett

5. An OHP Proposal

In Section 4, we described the OHP as a family of protocols, one per Sproc. In this section, we present a proposal for how these protocols can be generated and how they should be defined. Of course, because the set of Sproc protocols is open, all members of the set cannot be specified. Here, we address one particular Sproc protocol - one that handles navigation. Composition and IR protocols are not defined here, but should be the focus of the OHSWG in the short term.

The OSI seven layer model [Hebrawi 1993] describes connections between programs. It allows one to concentrate on one aspect of connectivity by focusing on a particular layer in the model. The lowest layer concerns physical connectivity, while the highest layer describes application-level protocols.

Similarly, we find it useful to think about OHP protocols in an analogous layered way. Figure 9 illustrates a layered model approach to OHP protocols. The OSI Transport Layer (OSI Layer 4) guarantees reliable, ordered byte transport. It seems clear that we should consider building our protocols on top of such a layer, since we should not be concerned with error checking, message ordering, etc. The other three layers are considered below.

A protocol stack box diagram
Figure 9. An OHP Protocol Stack.


Peter J. Nürnberg, John J. Leggett
HRL, CSDL, Texas A&M
original page URL: http://jodi.ecs.soton.ac.uk/Articles/v01/i02/Nurnberg/proto.html