If we have the following classes
class Reader
{
    MediaWork media;
}
abstract class MediaWork
{
    String name;
}
class Newspaper extends MediaWork
{
    String editor;
}
class Magazine extends MediaWork
{
    int frequency;
}
where MediaWork uses "subclass-table" (so is persisted into NEWSPAPER, or MAGAZINE tables)
Our schema is currently generated with a single FK in the READER table, across to the first of the NEWSPAPER/MAGAZINE tables.

We need to change the schema so that we create multiple FK's in the READER table, one to each of MAGAZINE, NEWSPAPER, .. subclasses. We likely also need to change the insert/retrieval to operate like reference mappings.