Interface VegaLiteSpec

Vega-Lite's own sanctioned slot for third-party metadata, and the only home a JSON-authored or Altair-produced spec has for one.

usermeta.maidr carries a MaidrTraceDeclaration — what the chart means, where the drawing does not say. It belongs on the spec node that becomes one MAIDR layer: a single-view spec, a layer[i] child, a concat or facet leaf. A block on a composite parent names no one layer and is ignored with a warning.

The chart's title. An array is a title of several lines, drawn one under the other.

The mark, as a shorthand string or a mark def. interpolate is how Vega-Lite joins consecutive points: the step, step-before and step-after values draw a piecewise-constant staircase, the rest interpolate. innerRadius is what turns an arc pie into a doughnut — purely visual, so the two convert identically. extent is how far a composite mark's interval reaches — stderr, ci, stdev, iqr — which the adapter reads only when it has to aggregate the raw observations itself, or to tell an interquartile band from the rest. center is the statistic a composite mark's interval is centred on, mean or median.

Vega-Lite's name for a view, "for later reference". It also names the view's compiled marks -- p5_95_marks rather than layer_0_marks for a layer named p5-95, through varName -- and it is what a fan chart's percentile_band declaration names its bands by.

Whether a composite spec's children share a channel's scale or axis. A channel left out is shared, as Vega-Lite shares it.

Wrap column count for concat, wrapped facet (single-field form), and wrapped repeat (array form). Vega-Lite's default when omitted is an unbounded number of columns (a single row).