Examples for Usage of Functions

1. The following query counts the number of instances of Class:

   COUNT[Class/class]

   The result will look like

   119 in COUNT[Class / class]
   end

2. This query sums up the salaries of an Employee:

   SUM_Attribute[Bill/objname,Employee!salary/attrcat]

   Unfortunately, the result is returned everytime as a real number, even if the input numbers were integers.

   2.5001000000000e+04 in SUM_Attribute[Bill / objname, Employee!salary / attrcat]
   end

   You can use this function also in query class to compute the value of a ``computed_attribute'':

   QueryClass EmployeesWithSumSalaries isA Employee with
   computed_attribute
       sumsalary : Real
   constraint
       c: $ (~sumsalary in SUM_Attribute[this/objname,Employee!salary/attrcat]) $
   end

3. Complex computations can be made by using multiple functions in a row. This query returns the percentage of query classes wrt. the total number of classes.

   QueryClass PercentageOfQueryClasses isA Real with
   constraint
       c: $ exists i1,i2/Integer r/Real
       (i1 in COUNT[QueryClass/class]) and (i2 in COUNT[Class/class]) and
       (r in DIV[i1/r1,i2/r2]) and (this in MULT[100/r1,r/r2]) $
   end