I had proposed this change to the guys who run the litmus site. They had not responded, as they are in the middle of other changes. The other changes are, I think, orthogonal to these suggestions. I wanted to capture this suggestion before I lost it.
I think that this is the current structure (as I have reverse-engineered it) of the Litmus database.
I am proposing this, which I think will be much more flexible and will scale better in the long run. I am seeing a few slight errors, such as that there should be "0+" resources associated with a test, not "1+". But I think this is mostly correct.
The Category entity and its self-link allows a flexible categorization of the tests, but also allows a heirarchical categorization at the same time. The Resource entity would allow us to capture, for example, a URL as one resource of a "go to site of URL" test. Then associating 100 URLs with that test would be more flexible than creating 100 tests of the form "go to URL A", "go to URL B", etc. The Config entity would capture the type of machine and the versions of what is being run. This would be more flexible than, for example, creating a one version of test for Firefox 1.5, then a separate copy of the test for FireFox, then a separate copy of the test for Firefox 3, and so on.
If anyone has suggestions, please let me know.