Jon, you wrote
have used "data" both singular and plural, and in the particular
context I used it ("discographical data"), singular was appropriate,
at least as I remember using it.
Now, for those who still believe "data" must be plural in all contexts
(other than "word used as a word" usage, e.g. "The word 'data' is
oftentimes misused."), it would have been written "discographical data
set", or something equivalent.
If "data" is singular, what is "people"? What is the context in which "data" can be a singular noun, any more than "people" can ever be a singular noun?