I have this sentence:
Each of the datasets HapMap 6 and CEU HapMap 610 is stored in two schemas.
Background: a schema is a namespace within a database. Possible variations include:
[Each of/Both] the datasets HapMap 6 and CEU HapMap 610 [is/are]
stored in two schemas.
Each means I am referring to the databases separately. Both means I am referring to them together. I don't have strong reasons for preferring one of these over the other. I'm leaning towards each but without a strong reason. I would be glad to hear of strong reasons to prefer one.
As far as are vs. is, I think is goes with each because each is singular. Both is plural, so that should go with are. Is that correct?
On a side note, is there any reason to prefer "the datasets HapMap 6 and CEU HapMap 610" to "the HapMap 6 and CEU HapMap 610 datasets"?
Best Answer
The meaning of the sentence changes completely if you use each vs. both:
If you say: "Both the datasets ... are stored in two schemas." then you are saying that there is a total of two schemas. (but we don't know how the datasets are divided between the two schemas (50/50? 60/40? 90/10?))
If you say: "Each of the datasets ... is stored in two schemas." then you are saying that there is a total of four schemas: two for one dataset, and two for the other.
If you want to say that there are two schemas, and that one schema contains 100% of one dataset, and the other schema contains 100% of the other dataset, then you should say: "Each of the datasets ... is stored in a schema", or "Each of the datasets ... is stored in its own schema."
Both should only be used when you want to refer to the combination (sum) of two things: The car and driver both weigh 3,510 lbs. (If they each weighed 3,510 lbs, the driver would need to go on a diet)