(v13) Progress, extent and units
This page applies to Harlequin v13.1r0 and later; both Harlequin Core and Harlequin MultiRIP
There are some things which a timeline can represent for which progress has no meaning as well as some things where progress has meaning but there is no way of determining how far through you are. Such as when sending a job to a printer. There is no way that the printer can know how much of the job there is but it does know how much it has already processed. There are others where an overall length of a task is well known.
What progress means is up to whoever defines that particular type of timeline. You could represent a fuser unit with a timeline in that you can use the concept of timeline progress to report and monitor the fuser unit temperature.
To aid this, timelines do not have a single extent, they have a start and an end. The start does not have to be zero it could be any value you require. Timelines also have a unit in which these extents and progress are measured. The units could be bytes, pages or equally volts or degrees Celsius. We could represent a fuser unit as a timeline with a range of 0 to 400 degrees Celsius and report progress as being the current temperature. Equally, if the fuser unit is removed or in some way failed that could be reported by ending the timeline or aborting the timeline with an error report that uniquely identifies the part that has gone wrong by using a timeline reference.