  We present the design and prototype implementation of a scientific
visualization language called Zifazah for composing 3D visualizations of
diffusion tensor magnetic resonance imaging (DT-MRI or DTI) data. Unlike
existing tools allowing flexible customization of data visualizations that are
programmer-oriented, we focus on domain scientists as end users in order to
enable them to freely compose visualizations of their scientific data set. We
analyzed end-user descriptions extracted from interviews with neurologists and
physicians conducting clinical practices using DTI about how they would build
and use DTI visualizations to collect syntax and semantics for the language
design, and have discovered the elements and structure of the proposed
language. Zifazah makes use of the initial set of lexical terms and semantics
to provide a declarative language in the spirit of intuitive syntax and usage.
This work contributes three, among others, main design principles for
scientific visualization language design as well as a practice of such language
for DTI visualization with Zifazah. First, Zifazah incorporated visual symbolic
mapping based on color, size and shape, which is a sub-set of Bertin's taxonomy
migrated to scientific visualizations. Second, Zifazah is defined as a spatial
language whereby lexical representation of spatial relationship for 3D object
visualization and manipulations, which is characteristic of scientific data,
can be programmed. Third, built on top of Bertin's semiology, flexible data
encoding specifically for scientific visualizations is integrated in our
language in order to allow end users to achieve optimal visual composition at
their best. Along with sample scripts representative of our language design
features, some new DTI visualizations as the running results created by end
users using the novel visualization language have also been presented.
