The Application Server tests the validity of a calculation algorithm defined for a calculated feature before the calculated feature is executed. If the calculation algorithm for a calculated feature is invalid the execution is canceled or in case of manual execution is not even started. The Application Server will not test validity of a calculation algorithm when it is created or modified, it is therefore possible to store invalid calculation algorithms. The Application Server provides the possibility to test the validity of a calculation algorithm at any time.

Following rules must be matched for a calculation algorithm to be valid.

•There is at least one calculation in the algorithm

•There is exactly one final calculation (output of this calculation is not used as an input for another calculation)

•The structure of the type specific data of observations generated by the final calculation conforms to the feature type of the calculated feature.

•There is at least one calculation hat has either no input pin or whose input pins are all connected to features.

•The calculation algorithm has no loops where the output of one calculation is the input of a predecessor of this calculation.

•Each calculation in the algorithm is valid by

•None of the source features referenced in the algorithm are deleted

•All input pins are connected to features or other calculated features

•Input pins of type feature only are not connected to calculated features