The comments on ValueSet.compose.include has the following sentence about valuesets in the include:

> If one or more value sets are listed, the codes must be in all the value sets.

However, the ValueSet.compose.include.valueset element has this sentence:

> If multiple value sets are specified this includes the union of the contents of all of the referenced value sets.

The first sentence says that when multiple value sets are present, it's an "intersection" (codes must be in all value sets), but the second sentence says it's a "union".

Which interpretation is correct?