http://bserve.webhop.org/django_polymorphic/

It seems to do most of what I need (I’m experimenting with it now), since I need to M2M on a model that is polymorphic.

Yes, Abstract models are not without limitations, but they are very handy when sharing fields and methods across classes which inherit from them.

In the above example, there is no ‘Vehicle’ table in the database, so it makes sense that there are no ForeignKeys to it, even though it may be desirable.

Let’s say MackTruck had a mudflap=CharField() field. You are correct in that a Vehicle instance cannot access the .mudflap attribute (not all vehicles have mudflaps) , but that subclass can still use its own .mudflap attribute if instantiated as a MackTruck.

Django is awesome, but it can’t solve ALL problems

[Edit: fixed indentation error in Vehicle class]

You also can’t have any derived classes of the abstract model if they have their own fields.

For example, I have a generic MetaData object that my Task object owns. I want to be able to have any kind of MetaData and use polymorphic functions on MetaData that operate on the MetaDataSubclass’ fields.

“using InheritanceClassModel can impose serious performance hits on your queries because it has to look up not only the objects, but for each time you call .cast(), it must make an additional query on the class look-up table.”

If you look at the ContentTypes code, you’ll see that those queries are cached. The table look-up only happens for the first time when a specific class is called. If implemented properly, dynamic ContentType casting can be very efficient.

I brought up all these neat machine-learning (and just patient criteria matching) we could do to find potential trial patients to my physicians, and they liked the sound of it.

However it turns out that if you are looking at a patient’s past performance or prognoses, you are probably already too late to get them on a trial. The key is going to be analyzing schedules to provide lists of potential patients… in order to remind the MDs that there is a trial. The future is what is important, not the past.

We want to get a sick person treated as soon as possible, trial or not and having a retro-active trigger on monday for a patient seen friday afternoon just isn’t fast enough. There is still a lot to be done on this, obviously, but it’s exciting.

Docs may forget to document or forget about trials. However, orders are usually appropriate to the needs of the patients. Talk to attendings about what are usual chem orders for each of the disease that you have trials for, and if a group of orders comes along that suggests a certain ca is in the practice alert the coordinator. Other options are certain blood tests or types of CT or MRI orders.

Dont worry about false positives to the coordinator. If she finds just 10% of the patients flagged really are candidates for a trial she will be delighted. Actually, you want false positives. With the EMR it is trivial to look up the clinical details.

Steve