Normalization:

The automated process by which headings are compared for uniqueness to prevent duplicate headings and conflicts between records.  Under the rules of normalization, all diacritics and punctuation marks (except for the first comma) are removed, all letters are converted to uppercase, and modified letters are converted to their unmodified forms.  Subfield delimiters (but not subfield codes) are retained.  Headings that differ only in diacritics, marks of punctuation (except the first comma), or special characters normalize to the same form and are thus considered in conflict.  Such headings need to be further differentiated.  NACO normalization rules appear on the Web at:  http://www.loc.gov/aba/pcc/naco/normrule-2.html.  A full description is available in the DCM Z1.