the update attribute needs to be better described to communicate a sense of
its intended purpose; at present, section 4.7.5 only says "The upload attribute must return the associated XMLHttpRequestUpload object."
it says nothing about the function of the XMLHttpRequestUpload object and why, for example, there needs to be two distinct XMLHttpRequestEventTargets;
furthermore, the spec should state that the upload objects are distinct across different XMLHttpRequest objects (at the moment, this seems merely to be assumed); i.e., each distinct XMLHttpRequestUpload object is associated with a distinct XMLHttpRequest object
By the way, many thanks for all these reports!
(In reply to comment #2)
You added a note: "As indicated earlier, each XMLHttpRequest object has an associated XMLHttpRequestUpload object."
But this doesn't address my comment about whether XMLHttpRequestUpload objects are distinct or not; i.e., an implementer might (for whatever reason) reuse the same upload object on more than one request object. [You ask why? Because the spec allows this, or at least doesn't preclude this.]
It would be better if the word "distinct" were added in 4.7, i.e.,
"Each XMLHttpRequest object also has a distinct, associated XMLHttpRequestUpload object."