3 way one-to-many through a single link table

Question

I have 3 tables that are linked through one to many relationships in a single link table. Here's the real relationships:
assay(id)
multiplex(id, assays)
markerset(id, assays, multiplexes)
Here's the database schema:
assay(id, name)
markerset(id, name)
multiplex(id, name)
assay_marker_set(assay_id[not null], marker_set_id[not null], multiplex_id[nullable])
I've mapped one-to-many relationships between markersets and assays, and multiplexes and assays, and BOTH of these one-to-manys need to be writable. In the record creation process, assays are associated with markersets, and then assays are associated with multiplexes, which in turn are associated with markersets.
Here's our dilemma. When committing multiplexes through a unit of work, the one-to-many with assays can't see the one-to-many with markersets, so the commit fails because the markerset key is null.
We've gotten around the problem by creating a postSave() method in markerset that writes multiplex changes once they are created. But again, in a unitofwork commit, saving a markerset fires the postSave() method, which writes assays and multiplexes that have not yet been written to the database.
We've gotten around THAT by only turning on postSave() when creating multiplexes, not when associating assays with markersets.
My question is, is there a more conventional approach to this problem? Clearly, the database needs to be reworked, but time constraints and the quantity of data to be curated makes changing the schema impossible. Or have we arrived at the most sensible solution to a ridiculous problem? Currently what we have works, it's just incredibly complicated, and nearly unmaintainable.
Thanks for the time to even read this post, and mocking is permitted ;-)
Paul Cooper
GlaxoSmithKline US Bioinformatics

Answer 1

Looks like your object model does not match your data model.
From you object model you seem to have,
Assay
MarkerSet 1-m Assay, 1-m Multiplex
Multiplex 1-m Assay
From your data model you have,
Assay 1-m AssayMarkerSetAssociation
MarkerSet 1-m AssayMarkerSetAssociation
Multiplex 1-m AssayMarkerSetAssociation
AssayMarkerSetAssociation 1-1 Assay, 1-1 MarkerSet, 1-1 Multiplex
(your object model seems to be also missing the name)
I'm not exactly sure how you have your mapping working, but it would seem the best solution is to introduce an AssayMarkerSetAssociation object into your object model.
If you do not wish to use this object in your model, you could just use it internally to store the relationship and still have get/set methods for the relationships that you want that initialize themselves from the associations.
So your object model would be,
Assay
MarkerSet 1-m AssayMarkerSetAssociation (+ getAssays, getMultiplexes methods)
Multiplex 1-m AssayMarkerSetAssociation (+ getAssays, method)
AssayMarkerSetAssociation 1-1 Assay, 1-1 MarkerSet, 1-1 Multiplex
In general you seem to be able to get your mapping working without changing your object model, but are probably better off for maintainability to change your model slightly.