Purpose: describe events list format.

Audience: interested scientists

Events lists are useful but under-supported abstraction. Users can create an ascii file and then use it as an events list, but they need to use the eventsListColumn keyword to cause it to be parsed as such. This document proposes that they become more accessible by getting rid of the need for the keyword, and allowing a special scheme to be recognized automatically.

An events list is a list of time intervals, which is often associated with a label and color for plotting. The events bar is used to render an events list onto the canvas, and a mouse click on an event will cause the message to be displayed in a tooltip.

An ASCII file with the first two columns as ISO8601 times and no more than four columns, will be treated as an events list. For example an ASCII file containing multiples of any of the following records would be treated as an events list:

2015-07-11T00:00 2015-08-11T00:00
2012-09-05T18:00:25.676Z 2012-09-06T02:59:24.361Z       18
2015-07-11T08:00, 2015-07-11T12:00, 0x00FF00, "Garage Sale"

When four columns are found, and the third column could be interpreted as an RGB color, it is interpreted as such.

When ordinal data has DEPEND_0 with DELTA_PLUS and DELTA_MINUS, then this is interpreted as an events list. (TODO: find example that demonstrates.)

I've hesitated in making this choice because I'm pretty sure I've seen ASCII files with two times that are not a range. For example, you have a file with spacecraft time and then ground receive time, and then a bunch of associated data. I'm pretty sure this file had more than four columns, so Autoplot would not assume the interpretation, and for that matter additional keywords would allow the old interpretation to work.

Consider PNGWalk Tool's annotation facility and events lists. Perhaps if the label is a URL, starting with http://, then we can look up the http.