-- Definition -- An identity base for hydrographic (including man-made) objects in the real world. -- Description -- NOTE Derived 'views' of real-world hydrographic objects are represented through specialisations in other application schemas; all representations of the same real-world object share a common geographic name or hydrographic identifier.
-- Definition -- A hydrographic thematic identifier. -- Description -- NOTE May be used to hold a national hydrological identification code.