In metadata, an indicator is a Boolean value that may contain only the values true or false. The definition of an Indicator must include the meaning of a true value and should also include the meaning if the value is false.
If a data element may take another value to represent e.g. unknown or not applicable, then a Code should be used instead of an Indicator, and the meanings of all possible values should be clearly defined.
The suffix Indicator is used in ISO/IEC 11179 metadata registry standard as a representation term.
An example use of the Indicator suffix is if an XML document was required to contain the passing status of a Student in a statewide assessment. The data element would be: