Problems in the design and implementation of a GKS-based user interface for a graphical information system

Visvalingam, Maheswari

Abstract

State-of-the-art Graphical (mainly Geographical)
Information Systems (GIS) began life in the early 1970s and
are now well established on multi-user computer systems.
They support the capture, storage, retrieval, mathematical
manipulation and display of spatially referenced data.
Current GIS do not support the interactive exploration nor
the validation of multivariate data. We have researched the
potential offered by the ICL PERO graphics workstation and
its implementation of the Graphical Kernel System (GKS) for
the development of a GIS that would also facilitate
interactive data exploration and concept refinement.

The design of the GIS confined the use of GKS to the
user interface process. Whilst the concept of input classes
in GKS is welcomed, nevertheless the current provisions are
inadequate for the style of interaction required in a GIS.
The categories of input classes are neither exhaustive nor
mutually exclusive and merit a revision of concepts and
functions. The functions of the user interface were
consequently distributed between two co-operating processes
and the use of GKS was limited to that responsible for
output.

The confinement of GKS to one process within the design
enabled the abstraction and clarification of the common
functions that a GIS layer immediately above GKS should
provide and the identification of a uniform, consistent and
effective user interface.

One of the main requirements proved to be for a block
manager to provide many of the functions of a window manager.
The concept of a graphic block is familiar to graphic
designers and cartographers but is missing in GKS where
single level segment storage does not facilitate its
expression. The block concept enables a collection of
segments to be manipulated as a whole without sacrificing the
facility for manipulating individual segments independently.
A graphic tool may write to several blocks and many tools may output to one block. The position paper elaborates upon the
attributes, implementation, significance and outstanding
problems of the concept of the block, which should be
incorporated within GKS.

The concept of a key is a further higher-level output
device used in graphic communication. The generation and
interpretation of drawings is eased by the use of a
well-defined specification which assigns a consistent meaning
to syntactic elements. The specification, which defines the
objects to be displayed and the conventions for their
symbolism, may remain implicit or be made explicit through a
key. Graphic symbolism relies ultimately upon the same
output primitives as identified in GKS. However, there is a
many-to-many relationship between keys and output primitives.
The position paper describes a convenient mechanism,
presently within the user interface, for definition and use
of keys for multiple symbolism, for parameterizing the
details of symbolism and for experimentation with creative
symbolism. There is scope for deriving a simple model of
output. The kernel need only cater for a single primitive,
point sets, a configurable output device called the key, and
a data record for additional control.

Citation

Visvalingam, M. Problems in the design and implementation of a GKS-based user interface for a graphical information system

• Working Paper Type: Discussion Paper
• Deposit Date: Mar 4, 2014
• Pages: 26
• Series Title: C.I.S.R.G. Discussion Papers (University of Hull Cartographic Information Systems Research Group)
• Series Number: 2
• Book Title: Problems in the design and implementation of a GKS-based user interface for a graphical information system
• Keywords: Cartography -- Data processing, Computer science
• Public URL: https://hull-repository.worktribe.com/output/459197