Skip to main content

Data states

Every value on an MDD page is in one of four states: valid, no data, stale or in alert. Each page shows the states the same way, so a reader who has learned one page can trust every other page.

Do: with no wind data the speed shows dashes and the needle is hidden. Don't: the last value and the needle stay on screen as if they were live.

Figure 1: A value with no data shows dashes, and its needle is hidden.

Show a valid value in the data colour​

A valid value is drawn in the data role, the brightest element on the page that is not an alert.

  • Source. ux/specs/pages/common.md, data states. Legibility.

Replace a missing value with dashes​

When a value has no data, its digits are replaced by dashes in the data role, and any needle or pointer that depends on it is hidden.

  • Reason. A frozen number or a needle left at its last angle looks exactly like a live reading. Dashes and a missing needle cannot be mistaken for data.
  • Example. The wind page in its no-data state shows dashes in place of the speed and hides both wind needles and the wind bug.
  • Source. ux/specs/pages/common.md, data states. ux/design/wind/BRIEF.md, page artboards and data each element shows.

Raise a cue when a data source changes​

When the source behind a value changes, for example from one wind instrument to another, the display raises a visual cue.

  • Reason. Two sources of the same quantity can disagree. A silent change of source looks like a sudden change in the data itself.
  • Source. MDD400 firmware architecture, SCY-SW-STRATEGY-MDD400ARCH-001, UX and HMI vision.

Show an alert beside the value it concerns​

A value in alert carries the alert triangle, in the alert role inside an alert_outline outline. The triangle sits clear of the digits, and the value itself keeps its data colour. The alert's behaviour is described under Alerts.

  • Reason. The digits must stay readable while the alert is showing, because the reader needs the value to judge the alert.
  • Source. ux/specs/pages/common.md, data states. ux/specs/pages/navigation.md, inside a cell.
Not yet ruled
  • How a stale value is shown, meaning a value that has stopped updating but has not yet been declared missing. The wind page's first build treats a stale value as no data. The time after which a value counts as stale is set in firmware and tuned on the display.
  • The form of the cue raised by a change of data source, and how a page shows which sources it is using.
  • The position of the alert triangle inside a data cell.

These are tracked in ux/specs/pages/common.md, navigation.md and the firmware architecture, SCY-SW-STRATEGY-MDD400ARCH-001.