Design Engineers can add rule extensions to perform a validity check that can’t be performed using any other rules supplied by the Product Manager. Rule extensions execute a program that interrogates any part of the database and returns a pass/fail based on what it finds. The program runs after all other rules have been checked during validation of a product configuration. If the returned value is pass, the product configuration is valid; if fail, invalid. For example, you can check the inventory of a specific part before allowing certain options to be selected:
If ((Option XYZ == Selected) AND (Part ABC!= In Stock)) Then Return (Invalid Configuration) Else Return (Valid Configuration)