1992
Computer Graphics
- / -
Annex 8 of Visualization
of International Relationship Networks
Software Modules
Relational database: The data is currently held and maintained in
an Advanced Revelation database (version 1.16) running on a Novell 286
network. The database has been specially developed as a text database with
facilities to manage networks of relationships between the records. It
is desirable that when the data is displayed in map form, interactive changes
to the map should be carried back as updates to the database. But since
the prime requirement is for publishable hardcopy maps, this requirement
may be sacrificed in the short term.
Map design: Several approaches may be taken to the problem of map
design:
-
(i) Network analysis This uses specialized extensions of sociometrics
to take data of the type described above and to position the elements in
relation to each other on the basis of various measures of distance, with
those most connected tending to be placed at the centre of a network and
those least connected at the periphery. The advantage of this approach
is that it endeavours to mirror the network on the basis of its internal
characteristics. A number of software packages exist to perform the necessary
computations. Various ways of describing a network and identifying key
components result from such analysis.
The disadvantage of such software is that it has been developed for relatively
small networks only (100 to 300 nodes). Few of the packages are designed
to permit mapping of the resultant network. Data is output in matrix form
only or as indices in relation to key elements. More seriously, such networks
when mapped result in maps which, although they reflect the data, are not
designed to enhance the comprehensibility of the data (other than in a
purely scientific sense). Such computations can consume considerable amounts
of computer time, even on fast machines.
This approach has been explored using test data from the UIA Revelation
database consisting of some 5,000 nodes. The work was done on a Mac II
using software developed at the University of Dartmouth by Joel Levine
of the Department of Mathematical Social Sciences. This software has not
been adapted to run under MS-DOS.
-
(ii) "Crude mapping" A simplistic approach could be
taken. This would involve positioning the nodes on a grid determined by
the subjects with which they are associated. Such a subject grid (with
positions determined by a 4 character identifier) is in use to categorize
the UIA data into some 3,000 categories. Relationships would then be plotted
between the nodes.
In this case comprehensibility is achieved through the link to the matrix
and not through determining the shape of the network. Use of a grid could
severely undermine the memorability of the network. It would however be
relatively easy to develop and quick to run. A key question would be what
kind of interaction it would be possible to have with such a map and whether
it would be possible to shift from a detailed focus on a specialized cell
of the grid to a wider focus and back (a zoom facility).
-
(iii) Topological manipulation In this approach, the network
of relationships between nodes would be simplified using topological constraints.
For example a string of interlinked nodes would be represented by a straight
line. The position of the nodes on the line might be equidistant or determined
by some logarithmic function based on the distance from the centre of the
line. The aim would be to introduce symmetry elements into the data so
that it acquires a distinct and memorable pattern or shape. Some of the
algorithms required presumably correspond to those of pattern recognition
problems.
Plotting: Once coordinates have been determined, software is required
to plot the network, whether onto the screen or onto a graph plotter. Many
packages exist for this purpose. A distinction should however be made here
between adequate quality plots (for working purposes) and high-quality
plots for publication in book form. The latter question is discussed later.
The problem in plotting is to be able to introduce distinguishing elements
into the plot. These may include variations in line thickness (corresponding
to some measure of importance or proximity), variations in node size (corresponding
to the number of connections to the node) and the introduction of identifying
labels for the nodes.
A key requirement is that the plot be made from the data as processed by
one of the above techniques, rather than from data which is manually input.
A distinction must also be made between a curve fitting approach and one
which passes through the nodes as is required here. A distinction also
needs to be made between plotting a graph (from left to right) and plotting
a network in which there is no privileged direction. The latter form is
more characteristic of CAD programs (see below).
Drawing: It is desirable to move towards an interactive approach
to the data. In other words, once a plot is made for a segment of the overall
network, editors should be able to modify the network. Such modifications
mighttake one of two forms. The first would consist of simply moving portions
of the plot to make it more comprehensible, making room for labels and
improving the aestheties. The second might also involve the capacity to
add or delete features from the network. It would of course be highly desirable
that the latter changes should be carried back into changes to the relational
database. This can raise severe problems of compatibility between the relational
database and the drawing/plotting software, whether in terms of software
or of intermediate files. Such features are available in many CAD programs.
It is however important to recognize that the CAD software is here used
to "design" logical or topological constructs rather than buildings
or mechanical parts. This is not a limitation but it may permit use of
simpler (and cheaper) CAD software.
It is appropriate to note that the variant of CAD software used for interactive
printed circuit board design (PCB) has many features of value to the present
application, especially the "auto-router" feature which positions
connections on the circuit board in the most economic manner (avoiding
cross-overs, etc). Unfortunately the positioning criteria do not make for
maximum comprehensibility.
Interface software: In the case of Advanced Revelation there exists
a software product CAD/Base which offers "complete integration of
CAD drawings with a database environment", via industry standard DXF
files. The drawing is viewed as a Revelation file and the drawing elements
as Revelation records and fields. The drawing exists as a master file in
both the Revelation and CAD environments. Changes in one environment are
reflected in the other automatically without any intermediate file conversion
required.
Clearly this offers interesting opportunities for using the network map
as a menu through which users can select individual nodes on which they
can immediately access additional text data.
High-quality graphic output: One objective is the production of
maps to be printed in book form. To achieve this one approach might be
to produce output in a form which can be handled by PC-TeX to create files
for output on a high quality laser printer.
Integration of features: It is possible that CAD/Base offers an
appropriate means of integrating the different features discussed above
(except the last). It is also possible that such a product, which is relatively
expensive, can be considered as "overkill", and that a more compact
approach would be more suitable and easier to make available to others.
If the emphasis is on the simpler strategy of generating hardcopy, this
would certainly be the case. To the extent that interaction with the data
is desirable, then more features would be required, even though only a
selection of standard CAD features would be necessary.
For the user, there is obviously great merit in ease of use as an adjunct
to normal text editing procedures. Ideally such a package would bear some
resemblance to the more sophisticated forms of "outliner", such
as MORE and INSPIRATION running on Apple machines. In these an essentially
hierarchical outline of topics can be opened up into standard text processing
or converted into bullet charts. What is required is an equivalent which
is tied into a relational database environment. The different approaches
to network "map design" noted above might then be options in
the way the data was manipulated for presentation, as is the case in standard
business graphics (bar charts, pie charts, etc).