is internal

operator

Return type: Switch
Returns:       A value of true if the entity is an internal entity, and false otherwise.

Syntax
entity ( is | isnt) internal


Purpose

An entity test that succeeds if the given entity is an internal entity.

is internal is primarily useful when testing the entities named by the values of entity or entities attributes. This test will always return false in an external-text-entity or external-data-entity rule.