THE DISTRIBUTED USER ORIENTED GEOGRAPHIC INFORMATION SYSTEMS
Domen Smole
DFG CONSULTING, d.o.o., Pivovarniska 8, 1000 Ljubljana, Slovenia — domen.dfg@moj.net
Commission VI, WG VI/3
KEY WORDS: user-oriented GIS, distributed environments, standards, geoportal, ontology
ABSTRACT:
To meet the growing needs for effective environmental management all kinds of relevant spatial data have to be provided upon
which, with the purpose of gaining new knowledge, specific information-retrieval methods can be applied. With the aim to provide
access to collected data to broadest audience possible, much effort has been put on transfering spatially aware datasets from
centralized into distributed environments, especially the Internet as the major representative of distributed systems. Bringing easy-
to-use GIS tools to the Internet is considered as a crucial step to the spatial data popularization. This paper outlines the main issues
on GIS technology, standards and dissemination of spatial data in distributed environments with an emphasis on user aspects.
1. INTRODUCTION
In the field of geographic information systems significant
changes have been going on during the last few years. The need
for global access and decentralized management of geographic
data is forcing the GIS community to establish an open GIS
architecture and to provide distributed geographic information
services.
There are estimations that more than 80% of all information
relates to location on the Earth (Burrough, McDonnell, 1998)
and only 10% of captured and stored data is ever effectivelly
exploited. On the other hand, we have been witnessing rapid
growth and popularization of different types of communication
media, especially the Internet and mobile phone networkings.
By utilizing modern means of communication, vast amounts of
(spatially located) data can be accessed and used practically by
anybody in a fast, competitive and economic way.
When planning implementation and deployment of distributed
GIS their pros and cons should be considered adequately. One
of the major drawbacks of distributed environment are slow and
unreliable network communications, heterogeneous hardware
and software platforms, differences in data formats etc.
(Sumrada, 2002a). In contrast, the main purpose of a distributed
geographic information system is to offer users an easy-to-use
tool for accessing spatial information and services anywhere,
anytime at a fair price. This paper focuses on technology,
standards and dissemination of spatial data issues regarding
distributed geographic information systems.
2. TECHNOLOGY
2.1 Introduction
GIS technology strongly depends on achievements in software
and database industry. The emergence of component based
software and broadly accessible distributed environments have
strongly influenced the functionality and the structure of GIS
software tools.
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First, a shift from huge, monolithic GIS applications to small
GIS applications, integrated from several components,
happened. This approach has resulted in one major advantage:
ability to implement user tailored GIS applications (included
GIS functionality covers only user needs and nothing more) at
an affordable price. And secondly, introducing GIS software
components to distributed environment made development of
distributed GIS even more possible.
2.2 Approaches
Internet is the biggest distributed system in the world and the
World Wide Web is its most frequently used service. This is
one of the reasons why the term “distributed GIS” is so often
interchanged with the term “Web GIS”. Therefore, it makes
sense to outline the major technological approaches regarding
the Web GIS.
Web GIS takes advantage of the intranet/Internet client-server
architecture and the TCP/IP protocol (Friebe, 2001). In this
respect, GIS software logic is split between a client and the
server. The so called server-side approach is an approach where
the majority of GIS functionality resides on the server in
contrast to the client-side approach, where GIS functionality
resides on the client side (Ralston, 2002). Generally speaking, it
is impossible to say which approach is the best, it depends on
user needs, application specific requirements etc.
During the early stages of conveying distributed GIS concepts
into practice, it became evident, that two distinct approaches,
one for intranet in one for Internet, shall be taken. Intranet is
faster and more secure environment than Internet. Besides,
specific intranet user needs and requirements are more complex
and can be foreseen in advance, which is not always true for the
wide and versatile Internet audience. Intranet GIS solutions
usually take advantage of the already mentioned client-side
approach.
In the case of the client-side approach, the functionality is
provided by GIS software in the form of ActiveX components
(Microsoft technology) or Java applets (Sun Microsystems
technology), which must be downloaded and installed on the
