Unified Modeling Language Reference Manual, The, Second Edition

visibility

An enumeration whose value (public, protected, private, or package) denotes whether the model element to which it refers may be seen outside its enclosing namespace.

See also import for a discussion of visibility rules applied to interpackage references.

Semantics

Visibility declares the ability of a modeling element to reference an element that is in a different namespace from the referencing element. Visibility is part of the relationship between an element and the container that holds it. The container may be a package, class, or some other namespace. There are three predefined visibilities.

public	Any element that can see the container can also see the indicated element.
protected	Only an element within the container or a descendant ...