Schema hierarchy

The types in a schema are arranged in a hierarchy. If a type is subordinate to another type, it is called a subtype. The type on the branch stemming above a specific type is called its supertype.

Subtypes have more specific properties. For example, two different kinds of fields, Name and Date, may be defined as subtypes of Field.

The item type Field describes any field. The item types Date and Name are more specific kinds of fields. In a classification hierarchy such as this, the deeper the subtype is in the type tree, the more specific the data characteristics.

Example scenario

Imagine that a schema represents your house. There is a type for the entire house (House). A type for each room (Bathroom, Bedroom, and so on), and types for the different furnishings in these rooms (Bed, Chair, and so on). Each type represents a complete object. A house is made up of rooms. Inside these rooms are beds, chairs, couches, and so on. You know this, but you cannot see it by looking at the classification hierarchy view of the schema. You must open one of the types in the group view to see its components.


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