THE DATA MODEL • geographical variation in the real world is infinitely complex o the closer you look, the more detail you see, almost without limit • it would take an infinitely large database to capture the real world precisely o data must somehow be reduced to a finite and manageable quantity by a process of generalization or abstraction o geographical variation must be represented in terms of discrete elements or objects • the rules used to convert real geographical variation into discrete objects is the data model o Tsichritzis and Lochovsky (1977) define a data model as "a set of guidelines for the representation of the logical organization of the data in a database. .. (consisting) of named logical units of data and the relationships between them."1 • current GISs differ according the way in which they organize reality through the data model • each model tends to fit certain types of data and applications better than others • the data model chosen for a particular project or application is also influenced by:
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