# Overview of rules

Note: Rules are defined in the Central Designer application as part of the study design. You can view, modify, and run the rules using the InForm user interface. Oracle recommends that all rule design and modifications be performed using the Central Designer application.

A rule is a script that runs in the context of one or more specific items on a form, that checks whether data is valid, or that sets the value of an item based on a calculation, when data in the item is added or updated.

The InForm application uses rules to:

- Provide validation checks on entered data.
- Perform calculations that automatically determine the value of data items based on the value of related data items.
- Convert data from the units in which it is entered to normalized units that other rules can reference.
- Randomize subjects in order to assign drug kits to them.

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