04
ARCHITECTING DISTRIBUTED GEO-INFORMATION SERVICES:
BEYOND DATA INFRASTRUCTURES
Javier Morales, Mostafa Radwan
International Institute for Geo-information Science and Earth Observation (ITC), Enschede, The Netherlands
jmorales@itc.nl, radwan@itc.nl
Commission IV, WG IV/4
KEY WORDS: System Design, Specification, Abstraction, Requirements, Open Systems, Infrastructure, Distributed,
Value-added.
ABSTRACT
During the last decade technological developments have facilitated the access to geo-information and have made it easier
to manipulate, reducing the effort and skills required to ex
ploit it effectively. As a direct consequence of this trend, a
more sophisticated spatial awareness has developed among the general public resulting in geo-information being required
to support many daily activities. This is creating a growing dependence of people and organisations on geographic
information, which has converted geo-information into a precious resource. To support this new working environment,
the role of the traditional Geographic Data Infrastructure (GDI) has to change, from being a simple data discovery and
retrieval facility to become an integrated system suitable for the provision of customised information and services.
A service is a collection of functions or operations organised in a way that they exhibit a behaviour of value to a user. The
functions used within a service are provided by independent entities, and these functions are available at different system
nodes. Such services have to be formally specified before they can be properly implemented and used in a composition.
The internal structure of the service (i.e., the service realisation) describes how different components interact to provide a
desired information service.
In this paper we present our proposed architecture for a geo-service infrastructure and a design methodology that facilitates
the specification and access of distributed geo-services over the Internet (Web Serv
ices, Internet GIS, etc) in the context of
the GSI concept. The methodology proposes a repository service for creating, updating, validating, accessing and sharing
service models and service instances, using an XML-based interchange format.
1 INTRODUCTION
During the last decade technological developments have
facilitated the access to geo-information and have made it
easier to manipulate, reducing the effort and skills required
to exploit it effectively. As a consequence, the use of geo-
information is expanding beyond the traditional users (gov-
ernment organisations), to include new users communi-
ties (telecommunication industry, emergency services, and
tourism, a.o.).
As a direct consequence of this trend, a more sophisticated
spatial awareness has developed among the general pub-
lic resulting in geo-information being required to support
many daily activities. This is creating a growing depen-
dence of people and organisations on geographic infor-
mation, which has converted geo-information into a pre-
cious resource. However, more users that require geo-in-
formation for different applications means geo-informa-
tion providers have to deal with a large variety of specific
information requirements to satisfy. Dealing with these
requirements is a challenging task, specially taking into
account that the way geo-information information is per-
ceived, expected and used depends very much on the cur-
rent forms and shapes of markets and technology, which
make these requirements very dynamic.
Geo-information providers have realised that satisfying to-
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day's geo-information market, that is a variety of users
with appropriate geo-information services, in large vol-
umes and in near real-time mode, goes beyond the ca-
pacity of ‘single’ organisations. Therefore, these organ-
isations are seeking for mechanisms that enable them to
work together in a more collaborative way. To support
this new working environment, the role of the traditional
Geographic Data Infrastructure (GDI) has to change, from
being a simple data discovery and retrieval facility to be-
come an integrated system suitable for the provision of
customised information and services.
Our research is therefore focusing on the development of
mechanisms to describe, combine and manage indepen-
dent collections of services. This is because, what is re-
quired by today’s geo-information industry is a system that
enables geo-information providers to cooperate and work
together in an integrated way. Such system should make
it possible for providers to publish and share not only data
but business goals, processes, operations, resources, value-
added products, etc., unbundling in this way the function-
alities of current stand-alone geo-information systems, and
making them available as independently developed, yet in-
teroperable autonomous services. We called such a system
a Geo-information Service Infrastructure (GSI).
A GSl is a system from which specialised geo-information
products and services can be obtained by exploiting the
