# Relational routine
The Relational routine contains several functions which allow you to check affirmations based on boolean values.
You can access these functions by double-clicking the Relational node under the system routines folder in the Repository tree view.
Functions of the Relational routineFunctions of the RelationalRelational routine
| Function | Description | Syntax |
| --- | --- | --- |
| ISNULL | Checks if the variable provided is a null value.
It returns
true if the value is NULL and false if
the value is not NULL. | Relational.ISNULL(variable) |
| NOT | Returns the complement of the logical value of an expression. | Relational.NOT(expression) |
| isNull | Checks if the variable provided is a null value.
It returns
1 if the value is NULL and 0 if the
value is not NULL. | Relational.isNull(variable) |
To check the Relational routine, you can use the ISNULL function, along with a tJava component, for example:
```
String str = null;
System.out.println(Relational.ISNULL(str));
```
In this example, the test result is displayed in the Run view:
