Rector AL. What's in a code: Towards a formal account of the relation of ontologies and coding systems. In: Kuhn KA, Warren JR, Leong T-Y, (eds) Medinfo 2007. Belfus and Hanley; 2007. pp 730-734.

Correction.  The original version which appears in the proceedings incorrectly stated that "excludes" was the preferred mechanism for dealing with negative findings.  This has been corrected.  (See footnote 9 pg 5)

Please use this version for reference.