A good data definition provides ALL the characteristics forms (questionnaires, CRFs) and associated variables. What is needed is good old "TLV".

	Stands For..	Overview
T	Type of Variable	The most common types are dates, number, coded variables (e.g., 0 = No, 1 = Yes;).
L	Layout and Logic	Indicate the look and feel of the variable, and when it should be displayed (e.g., only show if subject is a male).
V	Validation	Indicate the rules that govern the acceptable variable values (acceptable range, units)

What To Do

Use A Spreadsheet

Document your data definition using the spreadsheet here.

Leverage Standards

Learn About Data Definition Standards (see here)

Mark It UP

When sending us a form, mark it up with the data definition.

Keep It Simple

Forms should use the cleanest, simplest layout possible. Standard practice is to use one-row-per-variable (examples here).

Leverage Visual Validation

A form's spatial and visual layout can be it's most important validation (see examples here).

Indicate Timing

Document which forms are collected with each study event by completing the Data Collection Schedule (see Data Collection Schedule.doc).

Data Definition Communication