The CISNA Model of Accessible Adaptive Hypermedia

A five-layer reference model for adaptive hypermedia, published at W4A 2008 with Steve Green and Elaine Pearson (doi:10.1145/1368044.1368052), and implemented as Carnforth-Java during doctoral research at Teesside.

What it is

The CISNA Model rebuilds the Dexter Reference Model of Hypertext for an era of script-heavy, AJAX-driven content, distinguishing five layers: Adaptation, Navigation, Semantics, Inventory, and External Content. Each layer is a formal model with its own diagrams and notation; bridges between layers express how meaning composes upward from raw content through to adapted presentation.

The published version (W4A 2008) presents the layered architecture and the formal definitions; the doctoral Java implementation (Carnforth-Java) applies the model to real interfaces. The Google Maps interface is the worked example used in the published material.

The five layers

  1. Adaptation — selects from the alternatives below based on user, device, and operating context. The layer where the recursive-design choice actually happens.
  2. Navigation — links and traversal between content elements. The original Dexter Model lives at this layer.
  3. Semantics — content composition and meaning, with notion ontologies, predicates, and rules.
  4. Inventory — formatted media elements available for use by the layers above.
  5. External Content — raw content beneath everything, usually networked.

Bridges between layers — Inventory↔Semantics and Semantics↔Navigation — express how meaning composes from raw content to adapted presentation. The bridges are formal: not metadata annotations on the side of the system, but typed relationships that the model compiler operates on.

The lineage

The CISNA Model is the published version of a longer published track:

  • 2006— “The Effectiveness of Self-Adapting User Interfaces as Assistive Technology for Handheld Mobile Devices.” Argues for intrinsic accessibility over functional bolt-on assistive tech, and names the formal next step (game theory + autonomous agents) that the 2029 framework resumes.
  • 2008— “20 Years On: the Dexter Model of Hypertext and its impact on web accessibility,” ACM SIGACCESS Newsletter. Critiques the Dexter Model and its descendant HTML for being structured around a printer’s view of a book rather than an author’s or a reader’s. Proposes the five-layer alternative that became CISNA.
  • 2008— “The CISNA Model of Accessible Adaptive Hypermedia,” W4A 2008, with Steve Green and Elaine Pearson (doi:10.1145/1368044.1368052). Published version of the five-layer model with formal definitions. This is what the literature cites.

What it became

The five-layer model is structurally a Shlaer-Mellor domain chart with peer relationships rather than the canonical SM client-server hierarchy. That deviation is itself a methodological contribution — see the Shlaer-Mellor lens for the recursive-design framing beneath it.

The Carnforth-Java XML notation and execution engine live on as Action Language, which now ships as a TypeScript port running in the browser with four worked examples.

The modern descendant in active use is the ActionLanguage intermediate representation (IR) inside Paradise — the same shape, the same threaded-interpreter execution model, applied to source-level accessibility analysis of JavaScript.

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