Accessibility described using Object Oriented Analysis and Design (OOA/OOD) – Part 10 Transcoding of Sequences

I’ve already written about my systems-led approach to accessibility research. This series of articles is designed to put a little more flesh on the bone with a detailed look at how OOA/OOD (Object Oriented Analysis and Design) can be used to describe computer systems and their interaction with users.

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Previous: Competition for resources

2.6 Transcoding of Sequences

The hope in describing the encounter between an entity and its users in terms of the relationships between capacity and capability is that those relationships can be populated on a case-by-case basis depending upon the current user of the interface.

Related to this, are concepts of augmentation and adaptation typical in current commercial assistive technology, exemplified by screen reading software such as Freedom Scientific Inc.’s Jaws for Windows application (Freedom Scientific Inc., 2010). Such existing assistive technology adapts default interaction modalities to match user need, often moving or augmenting presentation between the visual and sonic design spaces. Jaws for example, attempts to present the Microsoft Windows user interface in audio form.

In moving, and in particular, in augmenting presentation of content between design spaces, timing and general sequencing issues arise. For example if visual indication of “new message arrived” on a mobile phone is augmented with an ear-con for a low-vision user, what happens if the user acknowledges the indication before play out of the ear-con completes?

A further, more complex, example would be if the need for a higher priority use for audio output is identified, such as “Incoming call” whilst the audio channel is in use; this is an example of augmentation increasing the competition for severely limited resources. Selection of Shlaer and Mellor allowed this transcoding-in-a-competitive-environment problem to be considered through the use of assigner state models within domains, and within the bridges between domains.

Sequence transcoding may also be supported through the use of role migration within information models (discussed in later parts of this post).

Next: Role migration

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