<p>This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.</p> <p>An explicit formal-ontological representation of entities existing at multiple levels
of granularity is an urgent requirement for biomedical information processing. We
discuss some fundamental principles which can form a basis for such a representation.
We also comment on some of the implicit treatments of granularity in currently
available ontologies and terminologies (GO, FMA, SNOMED CT).</p>
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Comp Funct Genomics. 2004 Aug-Oct; 5(6-7):501-508