Represents a global Schema Component. That is, a type, element, attribute, model group, attribute group, or identity constraint.
Note that not all types, elements, and attributes are global; local types, element, and attributes do not appear in the global lookup table. Also note that other information items such as particles, facets, and so on are not globally indexed, so are not SchemaComponents.
@see SchemaType
@see SchemaGlobalElement
@see SchemaGlobalAttribute
@see SchemaAttributeGroup
@see SchemaModelGroup
@see SchemaIdentityConstraint