All modules share the same data models and data structure, and 
use a database management engine and an API library. Each 
subsystem has its own interface, which can be modified by the 
user. 
We can design the spatial object classes in C++ corresponding 
to the spatial data model in Figure 5. Each kind of spatial object 
uses a C++ class, but it is a temperary class unlike the classes 
in an object-oriented database management engine which are 
permanent. Every temperary class might have the same data 
members or more as its permanent class, because some 
control variables or additional information might be included in 
the temperary class. 
6. CONCLUSIONS 
Object-oriented approach can be applied to all aspects of the 
life-cycle of information processing. The main advantage of 
object-oriented approach is that the analysis and design of a 
system are consistent with its object models. This paper 
introduces the applications of object-oriented approach at 
various levels through the life-cycle of a GIS. Some advantages 
and potentialities have been clearly demonstrated. At this 
moment, the major obstacle for the widespread applications of 
object-oriented technology in GIS is the lack of popular object- 
oriented database management systems. Scientists and 
engineers have accepted the object-oriented programming 
languages as a main tool. The next step is to pay attention to the 
object-oriented database management system and object- 
oriented GIS. 
From the viewpoint of GIS development, the final resolutions 
of many problems might rely on object-oriented technology. 
Three dimensional GIS and temporal GISs need more 
complicated data models and concern more nested relations. 
Object-oriented data model and database management system 
can represent complex objects and nested relations. These 
might prove to be most promising for 3-D and 4-D GISs. 
Reference 
Chance, A., Newell, R., and Therault, D., 1990, An object- 
oriented GIS: Issues and solutions. In Proceedings of 
European Geographical Information Systems(EGIS)Annual 
Conference. pp. 179-188. 
Egenhofer, M. J., and Frank, A., 1987 Object-oriented 
database: database requirements for GIS. In Proceedings of 
the International GIS Symposium: The Research Agenda, 
Vol.2, pp. 189-211. 
Object-oriented 
data management in a GIS. 
Gong, Jianya and Li, Deren, 1992, 
models for thematic 
Australian Journal of Geodesy, Photogrammetry and 
Surveying, No. 56, pp. 37-48. 
Gong, Jianya and Li, Deren, 1992, An object-oriented 
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Archives of 17th ISPRS Congress, Washington, D.C., pp.772- 
779. 
Ishikawa, Hiroshi, 1993, Object-oriented database system -- 
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Verlag Publishing House 
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304 
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