Dear all,
I have the following design issues: an analysis is made of several tests. A test is performed measuring one parameter (given a unit of measure) by means of some methods. The test will produce an outcome, a measure of the parameter in the given unit of measure.
For example, Aluminium may be measured in mg using methods 1 and 2, or 2 and 3 (and these are two different tests).
The same parameter may be measured using different units, and they would be different tests. Same if the parameter changes, of course.
In some sense, tests are master data, since the same couple parameter-unit of measure can be measured in a given set of methods.
The outcome instead is generated after a test is selected and performed for an analysis.
See the following table as an example of possible tests.
TestID Parameter UM Methods 1 Al mg method1, method2 2 Al mg method2, method3 3 Al ml method4 4 Cd mg method3, method4
At run-time, the lab technician will select testID 1 and perform the test, producing an outcome. The same test can be perfomed several times, but in different analyses, producing different outcomes.
At the same time, a parameter may have some limits, given the unit of measure, according to different destinations.
I thought about two possible design solutions, which I attach here. If you look at the E/R diagrams in both files you can see the two options.
Basically, in the second DB, Lab2, I got rid of the table ParamUM, which simply puts together the parameter and a unit of measure.
Which do you prefer and why? Or are they equivalent? Thanks a lot.