"Each" vs. "both"

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"?

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)

• Like it, but I think your last paragraph is confusing. Each would be wrong, together right, but both there is just unclear (as narx pointed out). Oct 6, 2011 at 22:22

Both options that you are considering are unclear. In other words, each of the two is unclear. To be perfectly clear, say:

The datasets HapMap 6 and CEU HapMap 610 are each stored in an individual schema.

or

The datasets HapMap 6 and CEU HapMap 610 are stored in two separate schemas.

And then,

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?

Yes.

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?

No.

I would use "each" in your example. The reason is because of the slightly different meanings in each sentence.

"Each" means that HapMap 6 is stored in two schemas, and CEU HapMap 610 is stored in another two.
"Both" implies that HapMap 6 and CEU HapMap 610 are stored together in the same two schemas.

Thus, depending on the situation, one would choose "each" or "both". Also, when there are more than one options, "each" is used. For example, if we were talking about 500 cattle, we would use "each":

Each of the 500 heads of oxen had one horn and a brown ear.
not
Both of the 500 heads of oxen had one horn and a brown ear.

As you can see, "both" can only be used if there are only two choices, and if the choices exceed two, "each is used instead.

And in answer to your sidenote, no, there's no reason to prefer one over another.

• So, in the case of both, the meaning is taken to be - "HapMap 6" & "CEU HapMap 610" are both in schema 1 and both in schema 2, making a total of 2 schemas? Hmm. Sorry, I was unable to parse "Also, when there are more than one options, "each" is used." Can you elaborate? Sep 14, 2011 at 5:50
• The plural of schema is schemas or schemata (I would prefer schemas for computers, and schemata for other uses), but not schema. Sep 14, 2011 at 12:30