ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS", Bangkok, May 23-25, 2001 
A COMMON DATA MODEL AND REQUESTING LANGUAGE FOR SPATIAL INFORMATION MARKETPLACES 
Matthew Y. C. PANG , Wenzhong SHI, Geoffrey SHEA 
Department of Land Surveying and Geo-informatics 
The Hong Kong Polytechnic University 
Hung Horn, Kowloon, Hong Kong 
Fax: (852) 2330 2994 
e-mail: matthew.pang@polyu.edu.hk 
Keywords: Spatial Internet marketplace, mediator, g-Commerce 
Abstract 
This paper investigates Spatial Information Marketplaces, its technical issues and applicability in the GIS industry. To facilitate 
g-Commerce (Geographical Commerce), this paper adopted a well-known business model in e-Commerce, namely electronic 
marketplace, into the market of geographical information (Gl) and geographical information services (GIServices). This new version of 
electronic marketplace is termed as Spatial Information Marketplaces. This paper discusses the essential characteristics and components 
in the marketplace. Follows that, the paper investigates the current developments and standards in geographical information 
interoperation. Accordingly, based on the structure of mediating server, a possible architecture of the marketplaces is proposed. The 
architecture makes use to the currently available standards developed by OpenGIS Consortium (OGC). Moreover, to cope with the needs 
in manipulating different service providers in the marketplace, the OGC’s simple feature model is extended and a common requesting 
language is developed accordingly. 
1. INTRODUCTION 
This paper investigates Spatial Information Marketplaces and its 
applicability and technical barriers in the GIS industry. Spatial 
Information Marketplaces consists of extremely devising services 
and applications. This paper examines an architecture for 
integrating heterogeneous service providers. The proposed 
architecture extends the available standards in the industry. 
According to a proposed architecture, a common data model and 
requesting language that manipulate services from the 
heterogeneous service providers are proposed. 
Electronic marketplaces have been used extensively in 
contemporary e-commerce applications. In an electronic 
marketplace, huge amounts of data and services are traded 
though the Internet. Both customers and providers in the 
marketplace usually interest in a same market area, for example, 
construction material. Improvements on efficiency, reduce 
overhead for both buyers and suppliers, speed up business 
process are advantages of electronic marketplaces [1]. 
Spatial Information Marketplaces is a spatial version of the 
electronic marketplace. In the Spatial Information Marketplaces, 
customers and providers trade in the market of geographical 
information (Gl) and geographical information services 
(GIServices). Since the Gl and GIServices are requested by 
customers on demand, costs spent on GIS developing and 
maintaining are greatly reduced. Moreover, the marketplace 
offers huge number of services from which users can choice at 
one single place in the Internet. GIService providers, such as 
traditional software vendors, Gl providers, and specialized spatial 
service providers expose themselves to an extremely large group 
of customers locating all over the world. Costs spent on 
advertisement and marketing are greatly reduced. Thus, the 
marketplace provides a win-win situation to both GIS software 
vendors and GIS users. 
The concept of spatial information marketplace is a step forward 
in the development of geospatial interoperability. Currently, the 
GIS industry focuses geoprocessing interoperability on sharing of 
geographic data set within and among geo-information 
communities (2]. The concept of spatial information marketplace 
facilitates a channel for delivering not only a sharable geographic 
data set but also a total solution of geoprocessing services. The 
new concept of geographic interoperability will absolutely prompt 
the uses of geographic information technology [3]. Although the 
spatial information marketplace is a new concept to the GIS 
community, these technologies and standards developed in the 
community are worthy foundations to its successful 
implementation. 
2. COMPONENTS OF SPATIAL INFORMATION 
MARKETPLACE 
A Spatial Information Marketplace shall consist of at least two 
major components, namely, service providers, and infrastructure. 
In a Spatial Information Marketplace, customers select services 
from a huge number of service providers. These providers can 
either offer on-line spatial data services (e.g. digital maps at 
various re-solutions) or computational services (e.g. overlay, 
digital terrain modelling, map production service) to users on 
receiving their orders [4]. Data service is understood as a 
collection of distributed geographic data sets that can be invoked 
in a uniform manner and in a single location [4]. For example, a 
spatial information marketplace can provide a unique requesting 
mechanism for demographic data and land use data are 
maintained in different data service providers. Computational (or 
functional) services refers tc a collection of geographic data 
manipulate functions those can be invoked from a single location 
[4]. Actual implementations of the functions are installed at the 
servers of their service providers. In the point of view of 
customers, instead of purchasing these complex and infrequently 
used functions, they can invoke the services whenever the 
services are needed. Furthermore, since services are maintained 
by professional persons, general users are benefited from the 
high quality services with minimum expenditure. Examples of 
computational services include noise-modelling service, 
three-dimensional surface modelling, optimal route finding 
service, marketing area analysis, and map coordinates 
transformation. 
Infrastructure of a Spatial Information Marketplace includes a 
standardized users interface, from which various services can be 
invoked. The interface should be user-friendly in order to maintain 
willingness for customers to purchase services. Moreover, the 
interface should possess a unique logical structure and a 
common requesting language for different types of services. 
Another element of the infrastructure is catalogue service in which 
services are descried in a logical order. Customers search and 
select services based on the descriptions provided in the 
catalogue. An additional software component of the infrastructure 
is mobile agent. The agent corporate the operation of GIService 
from multiple service providers, in order to accomplish a complex 
requirement from customer. Due to limited length of this paper, 
mobile agent will not be addressed in this paper. 
3. GEOGRAPHICAL INFORMATION INTEROPERATION 
Geographical information interoperation refers to openness, 
ability to exchange and commonality in user interaction in 
manipulating geographic information in a distributed computing 
environment. The technology is the backbone of Spatial 
Information Marketplaces. Successful implementation of the 
marketplace relies on a standard of geographical information 
interoperability among the customers and the service providers.