[mdx] MDQ questions

[David Waite]

Clarification on section 3.2.1:

This section says that if multiple IDs are supplied the result is the intersection of the IDs. I take this to mean that if I have a tag “foo” as a collection, and entity IDs “bar” and “baz”, of which only “baz” is associated with that tag, then:

/entities/foo #returns baz
/entities/bar #returns bar
/entities/foo+baz #returns baz
/entities/foo+bar #returns 404 to indicate no results - bar is not tagged with foo
/entities/bar+baz #returns 404 to indicate no results, bar and baz are different entities and thus have no intersection

There is no query for the tags above that would allow me to perform a union operation, where I get both bar and baz back. Correct?

Also, is there any guidance around ID ordering to promote caching? /entities/foo+bar and /entities/bar+foo are equivalent commands but not equivalent URLs, and thus would not share cache. Recommending or requiring ordering would promote cache hits.

-DW