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There are two types of Attributes
Simple
Each entity has a single atomic
value for the attribute.
For example, SSN or Sex.
Composite
The attribute may be composed of
several components. For example:
Address(Apt#, House#, Street,
City, State, ZipCode, Country), or Name(FirstName, MiddleName, LastName).
Composition may form a hierarchy
where some components are themselves composite.
Multi-valued
An entity may have multiple
values for that attribute. For example, Color of a CAR or Previous Degrees of a
STUDENT.
Denoted as {Color} or {Previous
Degrees}.
In general, composite and
multi-valued attributes may be nested arbitrarily to any number of levels,
although this is rare.
For example, Previous Degrees of
a STUDENT is a composite multi-valued attribute denoted by
{Previous Degrees (College, Year,
Degree, Field)}
Multiple Previous Degrees values
can exist. Each has four subcomponent attributes: College, Year, Degree, Field
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