| unit | names the unit used for the measurement | Status | Optional |  | Datatype |  |  | Suggested values include: | cm(centimetres) mm(millimetres) in(inches) lineslines of textchars(characters) characters of text
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    | quantity | specifies the length in the units specified | 
    | extent | indicates the size of the object concerned using a project-specific vocabulary combining
        quantity and units in a single string of words. | Status | Optional |  | Datatype | 1–∞ occurrences of separated by whitespace |  | Values | any measurement phrase, e.g. 25 letters, 2 × 3
      inches. |  | <gap extent="5 words"/> |  | <height extent="half the page"/> | 
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    | precision | characterizes the precision of the values specified by the other attributes. | 
    | scope | where the measurement summarizes more than one observation, specifies the applicability
        of this measurement. | Status | Optional |  | Datatype |  |  | Sample values include: | allmeasurement applies to all instances.mostmeasurement applies to most of the instances inspected.rangemeasurement applies to only the specified range of instances.
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