Refget Sequences start/end query parameter and range request corner cases

[jmarshall]

The specification is not explicit as to whether clients must use either both or neither of start=… and end=… query parameters, or if just one of them may also be used. If it is permissible to use start=… by itself or end=… by itself, the specification is not explicit about what that should mean.

The specification does not specify what should happen when a request contains an end query parameter larger than the total sequence length. Reasonable behaviours could be to return a sub-sequence from start to the end of the sequence (i.e., “clipping” the end value) or to fail with Bad Request (as the requested end is out of bounds).

Note that the specification does say that out of bounds Range requests must fail with Bad Request. However this is inconsistent with RFC 7233, which specifies that out of bounds last‑byte‑pos is to be clipped while out of bounds first‑byte‑pos is unsatisfiable so should fail.

[nsheff]

At this point, we could just update the spec to reflect what the reference implementation actually does.

[andrewyatz]

I mean I am okay with it clipping if that is better behaviour and consistent with RFC 7233.

In the other cases though the compliance suite I believe allows for start or end to be omitted, one used or both used