One of the important tasks associated with the design phase of a materials properties database is defining and understanding the exact nature of the data to be stored in the database. Among the key questions are: (1) What are the data types: character strings, numbers, numerical arrays, graphics, images? (2) For numerical data, what is their format: integer, floating point, exponential? How many decimals? How many significant figures? (3) What metadata need to be associated with the data, and what is their form?