{
  "$schema": "https://vega.github.io/schema/vega-lite/v3.json",
  "description": "A simple bar chart with embedded data.",
  "data": {
    "values": [
      {"a": "A","b": 28}, {"a": "B","b": 55}
    ]
  },

  "layer": [{
    "mark": "rule",
    "encoding": {
      "x": {"field": "a", "type": "ordinal", "sort": ["B", "A"]},
      "y": {"field": "b", "type": "quantitative"}
    }
  },{
    "mark": "circle",
    "encoding": {
      "x": {"field": "a", "type": "ordinal"},
      "y": {"field": "b", "type": "quantitative"}
    }
  }]
}