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1. Introduction
GIS (Geographic Information System) data modelling is a methodology for designing spatial databases, a type of design activity of its own. However, the way database designer designs a database is distinctively different from the way urban designer designs a city. Why do we need database, the spatial database in particular, for urban design? How could we make use of the spatial database management system (DBMS) technology in the urban design application? To what extent the currently available DBMS technology could be applied to the urban design process? Based on these preliminary questions, the GIS database research will be moved a few steps further through the elaboration of theory and urban design case studies.

Judging from the vast amount of information concerned by urban designers, urban design definitely needs tools to manage this information. GIS has a track record in handling urban information, especially in the field of urban planning (Brail & Klosterman, 2001; Han & Kim, 1990; Zaki, 1998, Laurini, 2001). In the recent development of GIS technology, it begins to show potentials for the design-oriented uses. The way GIS will support design process is through its spatial database, with its competitive strength. The main function of spatial database is to store urban information in digital format for further GIS process, which composes queries, analysis, visualization, and simulation. A new design-supporting GIS function is proposed in the research work, which will use the spatial database as a sketching platform for urban design proposals.

To start with the discussion of data modelling, there is a crucial need to clarify the definitions of model and data model, when the term “model” has different implications and possible meanings in different disciplines. The definition of the model, according to system science, is the “representation of reality”, which selectively expresses certain relevant characteristics of the observed reality, and consists of objects or systems that exist, have existed or may exist. As a representation or an abstraction of the observed reality, a model is always a simplification of the complexity of reality, which makes the reality more understandable and operational (Crowther & Echenique, 1972).

Models may be classified as descriptive, predictive, explorative, or planning according to its purpose. Models can be classified based on their constructed elements, including physical models (solid materials such as architectural wood model), analogue models (drawings and plans), conceptual models (words or mathematical functions) and digital models (computer aided design drawings or data model). A model can be either static or dynamic regarding to its nature towards temporal elements.

A data model is not a physical building model, a city map, urban design drawings or a mathematical model of urban population growth. A data model is an abstraction of the real world that employs a set of data objects that support map display, query, editing and analysis (Zeiler, 1999). The data model can be applied to different aspects of the design process, such as procedure models, predictive models, digital urban models, behavioural models, dynamic agent-based models, etc. A data model, as discussed in this paper, is mainly descriptive, although it can function as explorative through customization. It is made of digital database and may be represented by analogical materials such as digital maps, plans and graphs. We propose that the GIS data model is to be designed as a bridge between urban reality and its spatial representation in GIS. It is the premeditated way to organize and represent the information of urban reality in a spatial database. Since all GIS-based analyses are supported by the spatial database, the data model is regarded as the foundation for urban design analysis and design decision-making.

In the area of computer aided architectural design (CAAD), the data modelling can now generate building system database for building management purpose. The data modelling can be utilized to support model-based building design using object-oriented CAD. For urban planning, the data modelling can be applied to the development of planning support systems (PSS). Unfortunately, the data modelling is not yet available for urban design purpose. A data model is designed for representing the relationships between buildings and their components. It is yet to be developed for an object-relational system (Cote, 2002). Using the test case of Singapore Management University’s (SMU) urban design, the paper will explore how the data modelling could be applied to the management of urban design guidelines.