The sheer variety of new information available on the Internet, in databases, and from other sources has changed the way they conduct business, undertake research, and communicate. One serious problem they need to address is that of ""dirty data"" - missing or inaccurate information that resides in the abundance and aggregation of data. Dirty data can have several pernicious effects. By some estimates, the problem of dirty data in industry has reached epidemic proportions. The problem is equally prevalent and potentially even more alarming in health care.