An abstract class template representing an entity de/coder, over a specific set of entities.
An abstract class encapsulating a set of entities for en/decoding. A typical example is the various html entities which are required to be encoded, for
Template class for xml / html / xhtml / etc (markup language) entity en/decoders, which share basically the same entity encoding scheme, only differing in the exact entities which must be encoded. (The html entities are a superset of the xml entities, for example.)