The global LoopBase element is the head of a substitution group whose members define loops. Any element that is a member of the group may be substituted for the LoopBase element anywhere the LoopBase element may be used in an instance file.
The optional size attribute defines a recommended size for visualization of an infinite drawable element such as plane, cylinder, axis, etc., or objects without explicit geometric parameters (e.g. coordinate system).
The optional transparency attribute defines the transparency property of a model entity.
Source
<xs:element name="LoopBase" type="LoopBaseType" abstract="true"><xs:annotation><xs:documentation>The global LoopBase element is the head of a substitution group whose members define loops. Any element that is a member of the group may be substituted for the LoopBase element anywhere the LoopBase element may be used in an instance file.</xs:documentation></xs:annotation></xs:element>