The formal definition of a derived entity and derived architecture:
derived_entity_declaration ::=
entity identifier is new entity_name with
derived_entity_header
derived_entity_declarative_part
[ begin
derived_entity_statement_part ]
end [ entity ] [ entity_simple_name ];
derived_architecture_body ::=
architecture identifier of entity_name_#1 is
new [abstract] architecture_name
[of entity_name_#2] with
derived_architecture_declarative_part
begin
derived_architecture_statement_part
end [architecture] [architecture_simple_name];
To ensure compatibility of architecture inheritance with entity inheritance, one of the following cases must be fulfilled:
- entity_name_#2 is omitted. In this case it is assumed to be equal to entity_name_#1.
- both entity names denote the same entity
- the entity denoted by entity_name_#2 is in an ancestor of entity_name_#1.
It is an error if none of the above cases is true. Furthermore it is an error if architecture_name does not denote an architecture of entity_name_#2.
Due to the fact that a derived entity is a new primary unit, the formal definition of a primary unit needs to be extended:
primary_unit ::= entity_declaration| derived_entity_declaration -- new!
| configuration_declaration
| package_declaration