The ORM Foundation

How does ORM (and more specifically, NORMA) handle the modeling of derived values? For example, I'm currently working on a ORM model related to the concept of payroll deductions. A payroll deduction (object), in this case, has something like an "amount accrued YTD" value. (Payroll Deduction has AmountAccruedYTD)

The YTD amount is important to the business, but the value is derived elsewhere.

How can I represent the derivation of the value?

Thoughts?

Steve

Hi Steve,

From your example, it seems to me that something called "AmountAccruedYTD" would be derived from whatever it is that is being accrued.
From your description, I assume that each "deduction instance" is uniquely identified somewhere.

So it would seem to be a matter of "just" adding up the deductions between two points in time (e.g. "CurrentAccountingYearStartDate" and "CurrentAccrualCutoffDate") and putting the result into the "Amount AccruedYTD" column.    

Derivation is discussed extensively in the Big Brown Book (e.g. pages 98 onwards) and in NORMA Tutorial 2 which you can download from the library.
Also, there are quite a number of posts on this site about derivation. (e.g. try a site search using "derived".)

I don't think that "automatic derivation" is yet implemented in NORMA so we currently advise a textual annotation on the model.

Hope this helps

Ken

Great, I'll go through the 2nd tutorial. I'd gone through it before, but often these things take practice before they get stuck in your brain! :D

Thanks for the help!