Overview

Functions are special queries which have some input parameters and return exactly one object as result for one set of input parameters. Similar to builtin-queries, they are implemented by a PROLOG predicate which is defined either in the OB.builtin file (this file is part of every ConceptBase application) or in a LPI-file (see also section 5.2.2).

With the following predefined functions, one can make aggregations and simple arithmetic computations:

COUNT:

counts the instances of a class, this may be also a query class

SUM:

computes the sum of the instances of a class (must be reals or integers)

AVG:

computes the average of the instances of a class (must be reals or integers)

MAX:

gives the maximum of the instances of a class (wrt. the order of < and >, see section 2.2)

MIN:

gives the minimum of the instances of a class (wrt. the order of < and >, see section 2.2)

SUM_Attribute:

computes the sum of the attributes in the specified category of an object (must be reals or integers)

AVG_Attribute:

computes the average of the attributes in the specified category of an object (must be reals or integers)

MAX_Attribute:

gives the maximum of the attributes in the specified category of an object (wrt. the order of < and >, see section 2.2)

MIN_Attribute:

gives the minimum of the attributes in the specified category of an object (wrt. the order of < and >, see section 2.2)

PLUS:

computes the sum of two reals or integers

MINUS:

computes the difference of two reals or integers

MULT:

computes the product of two reals or integers

DIV:

computes the quotient of two reals or integers

ConcatenateStrings:

concatenates two string objects