DMN17 — the operation of is() function is not well specified

The new is() function is in a spec section called "Date and time functions" but it is unclear if it related only to date and time types. The examples only show date and time. Though it would seem reasonable that is also handled datetime type as well.

Additionally, it references section 10.3.2.2 for descriptions of semantics and that section deals with ore than just date and time. It also deals with other 'primitive' types - so it is unclear if is() relates to these also. Additionally, that section does not deal with other types like range/context/function/list so it is not clear if is() deals with all types in that section, and indeed other types as well.

By example, is it not evident if is({},{}) is true, false, or illegal. Similarly for is([1], [1]) or is(1,1), or is([null..2], < 2).

Additionally, it is also unclear (to me) from the semantic description whether is(@"2021-02-19T10:10:10Z", @"2021-02-19T10:10:10@Etc/GMT") as they are both UTC forms. The spec says they are 'comparable', but does that relate to is()?