Delta-X: A Federated Spatial Information Management System 
Ekow J. Otoo and Adel Mamhikoff 
Centre for Parallel and Distributed Computing 
School of Computer Science 
Carleton University 
Ottawa, Ontario, K1S 5B6 
Abstract 
Development of applications using Geographic Information Systems often requires access to sev- 
eral different data-sets. These data-sets are heterogeneous with respect to i) the underlying database 
management system, ii) the spatial and non-spatial data formats, iii) the data storage technology, 
etc. A considerable volume of the required data is not even maintained with any database technol- 
ogy. The data-sets are stored and delivered as simple files. This may be attributed to the fact that 
nated digital cartographic data collection preceded the development of databases technology. As a result, 
tor the data accessible to most users is legacy data. Spatial information systems, and in particular GIS 
at technologies, lack the unified integrated access to the multitude of different data types required 
ark for application development. The Delta-X federated spatial information management system is an 
approach to provide interoperability in a network of heterogeneous databases. It establishes in- 
teroperability between different relational DBMS's, simple files and object repositories. Using the 
e Delta-X approach, an agency can register a data-set, that 1s either maintained or not maintained by 
be an underlying database management system. 'This is made accessible to users through a distributed 
red virtual global schema definition. By this means, the independence and autonomy of control, of the 
individual data-sets registered in the federation, are still respected, while still maintaining some 
its integrated uniform access with respect to a particular GIS environment. 
ion. Keywords: distributed databases, interoperability, relational data model, object repositories. 
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