Aggregation functions

Aggregation functions are called in order to provide aggregated values for collections or on different aggregation levels. In an OSI SELECT statement or VIEW definition, aggregation functions may be referenced as data source for attributes in the statement.

All operations assigned to non-transient view or aggregation properties are considered as aggregation functions. Function names that do not match default aggregation function names are supposed to be implemented as user aggregation functions.

In order to provide extended information about data and levels, several service functions are provided, which may be overloaded in the aggregation schema.