Web Services and National Spatial Data Infrastructure (NSDI)
Cetin CÓMERT
KTU, Geodesy and Photogrammetry Department, 6108 Trabzon, Turkey
ccomert@ktu.edu.tr
Commission IV, WG IV/4
Spatial Data Infrastructures, TS
Keywords : Spatial Infrastructures, Data, Interoperability, Databases, National
ABSTRACT :
“Web Services” have gathered a great interest from various communities including business, industry, academia, and government.
Many successful implementations of Web services for business to business (B2B), government to business (G2B), and government to
citizen (G2C) applications are already in place. “Web Services” is a new paradigm where every different system or provider offers
some “services” for certain user groups. Any user does its job by just calling or combining proper services over Internet. If one is to
derive an analogy from the philosophical point of view, it should be the one between Web Services and Object-Orientation. Although
it has some weaknesses, Web Services seems to have a great potential for wherever there is a need for cooperation or
“interoperability”. This need had long been felt in spatial data management communities. These communities have also directed their
work towards the adoption of Web Services for their clear advantages over traditional models of interoperability. On the other hand,
National Spatial Data Infrastructures (NSDI) have traditionally been based on these interoperability models. In other words, as their
names imply, they have been “data-centric”. Whereas, it should not be difficult to predict the business models and supporting
technologies which will shape the future of spatial data communities considering the related developments in such areas as B2B.
From this respect, Web services have great potentials for NSDI. The purpose of this work is to examine this potential. To this end,
the paper will first introduce the current status of Web services. It will then present some implementations of web services within the
context of NSDI. Finally it will present a web services based infrastructure for the NSDI of Turkey.
1. INTRODUCTION
The need for interoperating applications has never bgen this
strong. This is felt rather strongly in the business-to-business
(B2B) sector, where every different company has applications
in their particular area of specialization. Nokia (2003) highlights
this need for the mobile community. The business model of
today necessitates the cooperation among these applications.
Consider different parties involved in a business trip reservation
for instance; at the requestors side there might be desktops,
mobile phones, or PDAs, while at the providers side there
would be airline, car rental, and hotel reservation systems. The
ultimate business goal here is to provide the requestor with a
high quality service that would enable him to effect his
bookings in a quick and an easy way. For this to happen, all the
systems involved should be able to “talk” to each other. And the
provision of this “talk” should be easy and cost-effective for
businesses to profit.
Interoperability can be defined as the ability by which different
applications can talk and cooperate with each other. The
differences may be in the hardware, software or the data
formats. To date, spatial data interoperability solutions have
been inefficient, proprietary, and complex. National Spatial
Data Infrastructures (NSDI) has emerged as the way enabling
interoperability throughout a country. NSDI would cut down
data production costs, improve spatial data access and use in a
country. To achieve this, a NSDI connects all the parties that
somehow use or produce spatial data via a computer network,
namely Internet. Although there have been achievements
concerning NSDIs in some developed countries, there are still
more to be done. This fact and the emergence of Web services
implicate improvements in NSDI implementations. That is why
some of the NSDI undertakings such as Canadian Geospatial
320
Data Infrastructure (CGDI) and major bodies such as Open GIS
Consortium (OGC) have directed their work towards Web
services (CGDI, 2001; Reed, 2002). Hence, NSDI
implementations have to be re-considered to adopt Web
Services technology. Although CGDI seems to pioneer in this
respect, there does not seem any implementation of web
services currently in CGDI (2004).
Web services have recently emerged as the next generation of
the Web. Two significant developments have made Web
Services a reality. One of them is Java which has provided
software and platform independence. The other one is XML,
which has enabled software and data independence (Nagappan
et al, 2003). Web Services has its roots on distributed systems
and it is an evolution of the work on that area. The philosophy
behind is the same, which is “distributed but cooperating"
- Systems. But the way that the “cooperation” takes place is
different. While the stress has been on the distribution of “data”
in distributed systems, it is on the distribution of the “tasks” in
Web services. In the Web Services view, every different system
or component offers some services for some others. And any
system does its job by just calling or combining suitable
services over Internet.
NSDI needs an interoperabilty infrastructure. Web services
seem to satisfy this need. Moving from this point on, we, in our
ongoing work, have designed and implemented a number of
Web Services for the Trabzon Municipality in Turkey. In doing
this, some of the activities of the Municipality have been
examined in detail in Sahin (2003). Then a number Web
Services have been identified and specified. Finally some of
these services were implemented using Cape Clear (Cape Clear,
2003) Web Services development and deployment software. We
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