Attributes are the physical characteristics that describe a person, place or thing. Attributes are "data." An entity usually has many attributes.

When storing data, the data architect/analyst must be aware of declaring data as atomic or non-atomic. Attributes should always be declared in its "atomic" or smallest form.

Let's use "DateOfBirth" as an example:

"DateOfBirth" is found in many databases and typically takes the form "mm/dd/yyyy." This data is stored in its "non-atomic" form. This data is made up of three elements, month, day and year. This attribute is not desireable because it must be manipilated to satify queries, such as "show me all customers born in July between the years 2000 and 2014."

"DatOfBirth" -- and ALL non-atomic data should always be stored in its "atomic" form: "BirthMonth," "BirthDay" and "BirthYear." Developers can easily concatenate "BirthMonth," "BirthDay" and "BirthYear" to express "DateOfBirth."