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==Data models==
most common representation for the data model are <br />
Provides a UML representation for geographic applications, it can represent the concept of field ,object and provide way to differentiate between spatial relation and simple association.
Represent a framework objects as classes which are partitioned into three kinds of classes, called simple classes, link classes, and path classes. Objects of a simple class are on the one hand just like objects in other models: They have an object type and an object identity and can have attributes whose values are either of a data type (e.g. integer, string) or of an object type (that is, an attribute may contain a reference to another object). So the structure of an object is basically that of a tuple or record. On the other hand, objects of a simple class are nodes of the database graph – the whole database can also be viewed as a single graph. Objects of a link class are like objects of a simple class but additionally contain two distinguished references to source and target objects (belonging to simple classes), which makes them edges of the database graph. Finally, an object of a path class is like an object of a simple class, but contains additionally a list of references to node and edge objects which form a path over the database graph.
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