A dashed entity is the graphical way of representing an entity that is inherited from a supertype and which needs to be used in the definition of the subtype. There are dashed block sets and process sets, services and gates.
The Z.100 terminology is existing entity .
An existing block set/block may be connected by channel, and these will then be there in addition to those specified in the super type.
An existing process set/service may be connected by signal routes, and these will then be there in addition to those specified in the super type.
An existing gate can have constraints in terms of signals on the endpoints of the gate specified, and these are then added to the inherited gate and will then apply in addition to those of the inherited gate.
In the PR version of a specification, inherited entities are simply identified by name.