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Information Technologies for Visually Impaired People
( ... ... ),
and additionally the reader knows he/she is reading a
fraction immediately from the first symbol. In the same kind
of idea, Nemeth uses 3 Braille characters: the beginning of
fraction, the fraction bar and the end of fraction
( ... ... ).
In order to reduce the length of simple numerical fractions,
in Marburg and British notations, the denominator
is written with lower numbers, that is, numbers that are
written in the lower part of the Braille cell. For instance
will be
3 Conversion to/from Mathematical Braille
In the last twenty years, various projects have been developed
in the field of Mathematical Braille notations, mainly
with the aim of facilitating the written communication between
sighted people and Braille readers in the field of Mathematics.
We will first focus on converters that allow conversions to be
performed between mainstream mathematical formats like
L A TEX and MathML and Braille notations.
These converters are used for different purposes. One is
to facilitate the production of scientific Braille documents.
Indeed it is much easier to produce a Mathematics document
in L A TEX or to use a word processor that supports
MathML than to write a document in Mathematical Braille.
Additionally a lot of resources are available in both these
formats. In the reverse conversion (from Braille notations
to mainstream formats) they allow sighted teachers or peers
to access to formulas written by blind students.
3.1 Labradoor
Labradoor (LAtex to BRAille DOOR) converts a full
L A TEX document including Mathematical formulas into
Marburg Braille or into HRTEX(see below). In addition, it
offers a rich variety of formatting capabilities, enabling the
production of Braille hard copies out of formatted L A TEX
documents [23]. As for conversion, one may choose between
two options: The mathematical contents of a L A TEX
document may be converted either to Marburg Braille Notation,
or to Human Readable TeX (HRTEX). The latter is a
code developed at the University of Linz, with the intention
to supply teaching materials in a way more easily readable
than TEX or L A TEX notation.
HRTEX is derived from TEX, although not compatible
with it. These are some of the most important differences:
Many symbols are abbreviated. For example, the
symbols for Greek letters are composed of the first two characters,
e.g., instead of \alpha we just write \al, instead
of \beta we write \be, etc.
.
The names of standard functions are written like
variables, but in upper case letters, e.g., we write SIN instead
of \sin, LOG instead of \log, etc.
Alternative notation for fractions: The fraction bar
is represented by two slashes -//-, and the whole fraction
is written as a group. For instance, instead of
\frac{a+b}{c+d} we write {a+b // c+d}.
As for formatting, Labradoor supports two output modes,
one for Braille hard copies, and one for electronic text. In
Hard Copy mode, elaborate text formatting algorithms suitable
to represent paragraphs, lists, tables etc. in an attractive
Braille layout are available. The table formatter deserves
special mention, because it is able to represent tables in a
variety of ways. Apart from the attempt to render a table in
Braille according to its natural layout, tables may be dissolved
according to their rows or columns. In Electronic
Text mode these sophisticated formatting tools are disabled.
3.2 MathML to Braille Converters
Various converters from MathML to Braille have recently
been developed. They allow transcribers to design
Mathematical content using mainstream Maths editors.
Bramanet [24] converts formulas from MathML to
French Braille. It is an application based on the XSLT technology.
It allows various settings including the possibility
to edit the output Braille table in order to fit with any hardware.
It comes with a script which automatically makes a
conversion from a document containing Maths formulas to
a document ready to be embossed in Braille.
math2braille [25] is a "self-contained Module’’ which
takes in a MathML file and outputs a Braille representation
of the same Maths. It is based on protocols and procedures
that have been developed in a previous project about access
to music. It produces Braille code in use in the Netherlands.
Stanley and Karshmer [26] propose a translator from
MathML to Nemeth Braille Code. The translation is performed
in 2 phases. First the MathML elements are translated
to Nemeth codes.
Then syntactic rules that are inherent to Nemeth code
are applied, such as the use of the numeric indicator, additional
spaces, and some contractions. These rules were fashioned
by Dr Nemeth to direct the conversion of Mathematics
into the Braille code.
3.3 Insight
Based on the MAVIS project [27] which was the first
solution to back-translation from Nemeth Braille code to
L A TEX, the Insight project [28] proposes a complete system
to translate Maths documents with mixed Grade II
Braille text and Nemeth code to L A TEX. The back-translator
is based on language semantics and logic programming.
The system processes an image of a Braille sheet (for
instance a scanned page) and recognises the Braille dots to
produce an ASCII Braille file. Text and Nemeth code are
automatically identified and separated to be separately translated.
Finally a single L A TEX document is produced to be
read by a sighted individual.
UPGRADE Vol. VIII, No. 2, April 2007 35