Classification aspects

Classifications are used in different ways, which express different aspects of a classification. Depending on the specific view, the importance of classification aspects for different classification may differ.

A general or conceptual classification consists of a list of (hierarchical) categories, which express a specific interest or view of the individual defining the classification categories. Defining proper classifications is an important issue, which sometimes may take years.

Typically, classifications apply on objects of a given type, i.e. general classifications are considered as typed classifications.

One important purpose for defining classifications is classifying individual objects, i.e. assigning objects to different well defined categories in order to determine the behavior of objects more precisely (only persons with sex female are able to get children ). Thus, classifying individual objects and creating specialized object types are similar processes.

Indeed, by classifying objects, these objects become more specific, i.e. they are associated with a more specific object type. Practically, categories are often not considered as sub types, but simply as categories ( male , female ) assigned to objects of a given object type ( person ). Considering, however, biological classifications, it becomes obvious, that each category defines a more specialized object type (animals --> birds --> swans).

Another common purpose of classifications is to divide individual object collections into a set of (hierarchical) subsets, i.e. a classification provides a collection schema for creating a number of classified collections from an individual abject collection.

Classified collections are often used for getting derived (aggregated) information from those collections. In order to define properties for aggregated values ( sum of income , count ), classified collections are considered as individual objects belonging to the same object type, which defines the characteristics for classified collections. Since different views to classified collections are possible, any number of object types might be defined for a set of classified collection, i.e. for a classification, which are called aggregation types .