The spec mentions some timelines (a "parallel timeline", "a GPU timeline", "a different timeline", "the offloaded timeline", etc...) but these timelines are not described anywhere. Meanwhile, #482 mentions a "device timeline" and "content timeline" (and, at the time of writing, there have been early discussions about whether an MLQueue is needed - which may or may not require a "queue timeline", as well)

These timelines should be clearly defined, including:

• their behavior on implementations that involve multiple devices and timelines (see Need to understand how WebNN supports implementation that involves multiple devices and timelines #350)
• their interactions with WebGPU's timelines