Cross-table anchored date needs onclause

[tim-band]

Where a table with a date references the same table with a "start" role date more than once, we need a DateAfterProposer per reference.

I'm pretty sure this can cause a crash right now, but I haven't tested it.

For example, imagine we have a Person table with a date_of_birth column which has the "start" role.

Then imagine we have a Procedure table with a "time_of_procedure" column, a "patient" column (referencing the Person table) and a "doctor" column (also referencing the Person table).

Then you want the proposals for time_of_procedure to include both:

• normal_date_fk [anchored to Person.date_of_birth via patient ]
• normal_date_fk [anchored to Person.date_of_birth via doctor ]