The growth of computer aided drawing systems for blind people (CADB) has long been recognised and
has increased in interest within the assistive technology research area. The representation of pictorial
data by blind and visually impaired (BVI) people has recently gathered momentum with research and
development; however, a survey of published literature on CADB reveals that only marginal research
has been focused on the use of a formal approach for on screen spatial orientation, creation and reuse
of graphics artefacts. To realise the full potential of CADB, such systems should possess attributes of
usability, spatial navigation and shape creation features without which blind users drawing activities
are less likely to be achieved. As a result of this, usable, effective and self-reliant CADB have arisen
from new assistive Technology (AT) research.
This thesis contributes a novel, abstract, formal approach that facilitates BVI users to navigate on
the screen, create computer graphics/diagrams using 2D shapes and user-defined images. Moreover,
the research addresses the specific issues involved with user language by formulating specific rules
that make BVI user interaction with the drawing effective and easier. The formal approach proposed
here is descriptive and it is specified at a level of abstraction above the concrete level of system
technologies. The proposed approach is unique in problem modelling and syntheses of an abstract
computer-based graphics/drawings using a formal set of user interaction commands. This technology
has been applied to enable blind users to independently construct drawings to satisfy their specific
needs without recourse to a specific technology and without the intervention of support workers. The
specification aims to be the foundation for a system scope, investigation guidelines and user-initiated
command-driven interaction. Such an approach will allow system designers and developers to proceed
with greater conceptual clarity than it is possible with current technologies that is built on concrete
system-driven prototypes.
In addition to the scope of the research the proposed model has been verified by various types
of blind users who have independently constructed drawings to satisfy their specific needs without
the intervention of support workers. The effectiveness and usability of the proposed approach has
been compared against conventional non-command driven drawing systems by different types of blind
users. The results confirm that the abstract formal approach proposed here using command-driven
means in the context of CADB enables greater comprehension by BVI users. The innovation can be
used for both educational and training purposes. The research, thereby sustaining the claim that the
abstract formal approach taken allows for the greater comprehension of the command-driven means in
the context of CADB, and how the specification aid the design of such a system
