Each table contains three columns. The first column is a description of the ConformanceGroup that the ConformanceUnit is part of (see 5.1). This allows the reader to easily find the ConformanceUnit. This column may also be empty, in which case the listed item is not a ConformanceUnit, but an included Profile or Facet. The second column is a brief description of the ConformanceUnit or included Profile or Facet. The last column indicates if the ConformanceUnit is optional or required. For an included Profile or Facet the last column is always crossed-out, indicating that the inclusion is mandated.