Consider an <Areal Feature> L representing an ECC_LAKE. The topology of L is represented by a <Regular Feature Face>, the outer boundary of which is defined by 2 <Feature Edge> instances, one defining the north shore of the ECC_LAKE, the other defining the south shore.
To indicate that these 2 <Feature Edge> instances define the outer boundary of the ECC_LAKE, they are components of an <External Feature Face Ring>, which is in turn a component of the <Regular Feature Face> specifying the topology of L. The <Edge Direction> associated with each <Feature Edge> indicates its orientation with respect to the <External Feature Face Ring>.
