The sheet identity element serves to compare sheets. By doing this, not the sheet areas are compared, but the fact is investigated, if an identical data object of the sheet type is concerned. One or more sheets can be entered. The comparing process takes place from the top downwards. The element returns a logic validity flag in case all sheets are identical. A special case is comparing one sheet. Here, the sheet is compared with an empty sheet, e.g. to test, if a valid sheet has been readed from a file.