A luminaire configured to receive DC power from an external power sourcing equipment and to exchange operational data with the power sourcing equipment, the luminaire comprising: - an interface unit comprising at least one connection unit configured to receive the DC power from the power sourcing equipment, to provide the DC power internally within the luminaire and to exchange operational data with the power sourcing equipment, characterized by: - a data processing unit connected to the interface unit and configured to compare the exchanged operational data with prestored allowed operational template data and to generate and store, in a storage unit, log data pertaining to unallowed operational data, the unallowed operational data being any exchanged operational data that does not correspond to the prestored allowed operational template data; and - a luminaire unit, which receives the DC power from the interface unit, configured to emit light in dependence on control information by executing operational instructions pertaining to that exchanged operational data corresponding to the prestored allowed operational template data, wherein the prestored allowed operational template data comprises data pertaining to instructions intended for one or more of: - switching on the light emittance of the luminaire unit, - switching off the light emittance of the luminaire unit, - changing the illumination intensity, by a predetermined amount, of the light emittance of the luminaire unit, and - changing the light spectrum, by a predetermined amount, of the light emittance of the luminaire unit. - an interface unit comprising at least one connection unit configured to receive the DC power from the power sourcing equipment, to provide the DC power internally within the luminaire and to exchange operational data with the power sourcing equipment, characterized by: - a data processing unit connected to the interface unit and configured to compare the exchanged operational data with prestored allowed operational template data and to generate and store, in a storage unit, log data pertaining to unallowed operational data, the unallowed operational data being any exchanged operational data that does not correspond to the prestored allowed operational template data; and - a luminaire unit, which receives the DC power from the interface unit, configured to emit light in dependence on control information by executing operational instructions pertaining to that exchanged operational data corresponding to the prestored allowed operational template data, wherein the prestored allowed operational template data comprises data pertaining to instructions intended for one or more of: - switching on the light emittance of the luminaire unit, - switching off the light emittance of the luminaire unit, - changing the illumination intensity, by a predetermined amount, of the light emittance of the luminaire unit, and - changing the light spectrum, by a predetermined amount, of the light emittance of the luminaire unit. - a data processing unit connected to the interface unit and configured to compare the exchanged operational data with prestored allowed operational template data and to generate and store, in a storage unit, log data pertaining to unallowed operational data, the unallowed operational data being any exchanged operational data that does not correspond to the prestored allowed operational template data; and - a luminaire unit, which receives the DC power from the interface unit, configured to emit light in dependence on control information by executing operational instructions pertaining to that exchanged operational data corresponding to the prestored allowed operational template data, - switching on the light emittance of the luminaire unit, - switching off the light emittance of the luminaire unit, - changing the illumination intensity, by a predetermined amount, of the light emittance of the luminaire unit, and - changing the light spectrum, by a predetermined amount, of the light emittance of the luminaire unit.