Envisioning information - The Visualization of Spatial Social Structure - page 10

Box 1.1 Creating the graphics

Acorn drawfiles were used to create the
illustrations in this topic.
In 1989 a library of procedures was
written

Essex

Hertford
shire

specifically to produce these

Greater

illustrations from data files.
Drawfiles are a sophisticated type of
computer record. The record contains a
list of objects, which can themselves be
a list of objects.
Object can include relationships
(with other objects), information (data
from other files) and:

London

re

Kent

Surrey

West

East

text - of a particular font, size, style and colour;
sprites - a pixelmap image (raster graphics);
paths - lines, curves and shapes (vector
graphics).

In the example above the Greater London 'object' has been shrunk. In the
drawfile it is tagged with its identification as County no. 1 and the relevant
boundary date (1981). Making up the group is its perimeter, the river Thames
and any islands in the river. All aspects of scaling, appropriate placement
and hyphenation of names and colouring are automated. This automation
was achieved by splitting names before parts of words such as 'shire' and
scaling label font size to the boundary box of each area drawn on the map.
Any feature of an object or group of objects can then be edited - interactively
on the screen - as has been done here.
Once a drawfile representing a particular geography has been created, it
can be transformed and additional information incorporated. For example,
the places could be represented by faces instead of polygons, re-coloured
and then merged with another drawfile.

'winding-rules' required to render complex topology. The rules have become
embedded in machine code, the hidden instructions that make the computer work.
As a result many more people can use computers, but a much lower proportion
of those who use them can alter what it is the computer does as compared to the
many programmers who could in the past. This lacuna was problematic for the
development of visualization in the 1990s but, as software improved, what once
had to be programmed became easier to create.