1. A method for maintaining a database in memory of a digital television receiver for display of digital television broadcast signals carried by a digital broadcast stream comprising system control data, the system control data comprising first information relating to an ATSC broadcast standard and also comprising second information relating to an MPEG-2 broadcast standard, the method comprising: receiving the digital broadcast stream; extracting the first information from the system control data; storing a first set of data entries from the extracted first information; extracting the second information from the system control data if the second information is present in the system control data; determining if the second information is consistent with the first information; and storing a second set of data entries only if the extracted second information is consistent with the first set of data entries.