Modelling spatial object behaviours in object- relational geodatabase
Bright Osei Twumasi · 2002
Modelling the behaviour of spatial objects constitutes a crucial aspect in the development of any GIS. Object behaviour, together with attributes and position constitute a minimal set of concepts sufficient to capture the special peculiarities of spatial data. Behaviour describes the dynamic aspects of objects. In the real world, we can observe several aspects of object behaviour. Objects in the real world follow their logical spatial arrangements; for example, a river network must always flow down hill, not uphill. Spatial objects have semantics, which describe the meaning or role of the objects in a particular application domain, and these impose conditions on the objects. Spatial objects also have relationships with each other and these relationships impose conditions or constraints on them. In addition, spatial objects change over time. In the context of spatial data handling, behaviour therefore describes the dynamics, interactions, relationships, constraints and semantics of objects in space and time. And any data model that represents (a part of) the real world should be able to capture these dynamic aspects of spatial objects. This will bring a geographic information system more close to the real world which it represents; and enable a more reliable use of the data in spatial planning and decision-making. Given the need to capture object behaviour, this research aims at utilising the object-oriented concepts to model spatial object behaviours and to realise these behaviours in object-relational geodatabase of ESRI. Spatial object behaviours have been investigated under three aspects, namely: consistency constraints, multiple representations and temporal behaviour. With respect to the consistency constraints, the research seeks to develop a methodology for on-line, automatic monitoring of constraint violations during updating of the database. With the multiple representations, the main issues dealt with are how to maintain topologic and attribute consistency between road areas and their centrelines. The temporal behaviour aims at maintaining the history of objects in the database. This research has developed an integrated model for the automatic enforcement of consistency constraints in the database, maintaining consistency between the multiple representations and keeping the history of objects in the geodatabase. A prototype implementation of the model has been carried on a topographic database. Some of the behaviours have been implemented, and fully realised by extending ESRI geodatabase model.