This property is added to the time:DurationDescription class to allow to express time duration also as xsd:duration. This is necessary because in the EEBus/E@h model time is always expressed as xsd:duration. We use this property to express the following time information in the EEBus/E@h model: – the startTime of the power sequence (in the PowerSequence class). SHALL be present – the endTime of the power sequence (in the PowerSequence class). If the value is available, it SHALL be denoted here. Otherwise the element SHALL be omitted. – the startTime of measurement as absolute or relative value (in the Measurement class). – the endTime of measurement as absolute or relative value (in the Measurement class). The duration is expected to be described as in xsd:duration