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Quantities

Accessibility survey data often contains unclear or aggregated definitions of quantities.

A11yJSON represents quantities either as string or as Quantity object with separate properties for value and unit. Both of the following definitions are valid and have the same meaning:

{
  "door": {
    "width": "90 cm",
  }
}

{
  "door": {
    "width": {
      "value": 90,
      "unit": "cm"
    }
  }
}

When you supply a string, any value + unit string that js-quantities supports as input is valid. Imperial or metric units, both works.

As the data representation is SI-unit based, you can use the resulting data with any system that supports SI units:

Besides value and unit, you can save the original data value as string representation as rawValue to debug conversion errors. When saving quantities, you have to specify them including their unit. You can provide measures as fixed quantities, but also with constraints and variance (uwing the accuracy field). This helps

  • when the measurement method is imprecise
  • when a person guesses a length, e.g., the width of a door
  • when you want to transform a averaged measurements of more than one object
  • when you derive the data from a catalog of criteria (e.g. when the original source states that all collected wheelchair-accessible entrance doors were more than 90cm wide, and only stores a boolean variable for this)