External variable idea
External variables represents results obtained by call external software (see External call). It can be for example displacements or stress extracted from finite element program output file. Esternal can also to represent derivatives of given result with respect to input variable (design or random) providing external software can compute derivatives (sensitivity analysis).
External variables table
External variable table contains set of external variables already defined in a project. User can add new design variable by pressing "Add" button. If Add is pressed, external variable definition dialog (described below) appears on the screen. If an user doubleclick on a variable in variables table design variable dialog is displayed in modification mode. It allows for update definition for given variable. User can also delete selected variables or duplicate it. It is very useful when several variables have to be defined with similar parameters.

Design variable definition dialog
External variable definition dialog is presented below. To define random variables user have to do as follows:
- Type unique name (taking into account any variables defined in the project)
- Check "is derivative" if defined variable is derivative. Otherwise uncheck.
- Select proper derivatives (if applicable).

External variables in main tree
External variables are also represented by items in main tree to open design variables list user can click on "External variables" item in the tree (in the picture below). Other way to open tis list is to click icon in the toolbar or in main menu Manage/Design variables.
