A Service Driven Approach for Integration
of
Heterogeneous Geospatial Data Repositories
S.K. Ghosh, Manoj Paul
School of Information Technology
Indian Institute of Technology, Kharagpur, India
skg@sit.iitkgp.ernet.in, mpaul@sit.iitkgp.ernet.in
ABSTRACT
Heterogeneous nature of geospatial data makes it difficult to be shared across organizations. In government and other agencies, geospatial data is often produced with diverse departments relying on a mix of software and information systems. Each department uses its individual system to increase efficiency, but sharing data across the enterprise is a near impossibility. In this paper, we discuss a service-based model for integrating diverse geospatial data repositories. The whole system works on publish-find-bind methodology of service oriented architecture. The service-oriented architecture using web services has been adopted for integrating diverse repositories of spatial data. The OGC (Open Geospatial Consortium) standards, namely, Web Map Service (WMS) and Web Feature Service (WFS), have been used for enabling a centralized access of spatial data of different format.
1. INTRODUCTION
In government and other agencies, Geographic Information System (GIS) is often developed with diverse departments relying on a mix of software and information systems. Each department uses its individual system to increase efficiency, but sharing data and applications across the enterprise is a near impossible. An increasing number of institutions are challenged with implementing robust geographic information system (GIS) capabilities for a large number of individuals through information sharing and interconnected networks. In the past, numerous technological roadblocks hampered the successful implementation of enterprise-wide GIS system (E-GIS). With the advent of high-speed networks; increasingly fast computers; intelligent, spatial-data serving technologies; improved data architecture; and advances in GIS software; the newest challenge involves integration of the various technological and institutional components, addressing the interoperability problem through OGC (Open Geospatial Consortium) standards (OGC, 2007). Enterprise geographic information system (E-GIS) is an organization-wide approach to GIS implementation, operation, and management. E-GIS can also be defined as an effort to design integrated geospatial management techniques to serve a complex institution.
In this paper we have followed a service-oriented architecture (SOA) using web services for integrating diverse repositories of spatial data. Two standard web service techniques proposed by OGC, namely Web Map Service (WMS) (OGC, 2004) and Web Feature Service (WFS) (OGC, 2002), have been used for enabling a centralized access of spatial data of different format. WFS allow a client to retrieve geospatial data from multiple Web Feature Services. The OGC WMS is capable of creating and displaying maps, coming simultaneously from multiple sources, in standard image formats such as .svg, .png, .gif or .jpg.
2. RELATED WORK
The need of sharing/integrating geospatial data available in various organizations has been addressed from quite some time (Taldoire, 2001). Several ways of integrating the spatial data repositories have been proposed in the literature. The database community has done extensive research for the integration architecture (Wiederhold, 1992).
(Roth, 1997) proposes a spatial data warehouse based technique and employing middleware technology for data exchange. This way data from multiple repositories are cleaned up and maintained in a warehouse. The warehouse can be composed of a central data repository or distributed data repositories depending on the design of the warehouse. (Cluet, 1998) proposes a mediation-based approach to facilitate data integration. Most of these approaches rely on the wrappers (Roth, 1997, Cluet, 1998) for accessing the data sources and translate the data in some standard format. The main advantage of the warehouse-based approach is that a local administration is required to maintain data. Mediator based approach, on the other hand, handles the queries directly through wrappers and integrates the data locally, which can be costly.
There are some works in the geo-spatial domain using open standards proposed by Open Geospatial Consortium (OGC) (Boucelma, 2003; Comert, 2004). An approach is proposed in (Boucelma, 2003) which uses a Web Feature Service (WFS) based mediation approach with the help of derived wrappers. The advantages over the other approach are that it can capture query capabilities available at the source or access a local query capability not available at the source. This enables an enhanced and efficient query language on spatial data. A spatial web application using open standards is also proposed in (Anderson, 2003).
In this paper we propose a web service based approach for the integration architecture. The data repositories are available on the web as services with some well-defined interface. It is base on XML technology and a client can access any data repository having data in any format located on any platform if it only knows how to communicate with service provider. The goal is to provide unified access to data from heterogeneous data providers. Any client (user) can submit its query to a geospatial server. The server, on the other hand, will retrieve the data from the multiple sources and return the result to the client. This will help in realizing interoperability between the heterogeneous data repositories.