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. Author manuscript; available in PMC: 2011 Apr 1.
Published in final edited form as: Mol Reprod Dev. 2010 Apr;77(4):314–329. doi: 10.1002/mrd.21130

Figure 1.

Figure 1

A) A simple list of keywords for anatomical structures in the limbs does not provide information about how the keywords relate to one another. B) The use of a hierarchy allows a simple view of how the structures of the limbs can relate to one another. In this case the hierarchy describes parts of the limbs, but does not relate the upper parts of the forelimb and hindlimb. C) The use of a directed acyclic graph permits terms to have more than one parent and provides a robust representation of the anatomy of limbs. In this tree-view of a simplified ontology, the upper leg bone is both a part_of the upper leg and is_a hindlimb bone. The boxed “I” denotes an is_a relationship and the circled “P” denotes a part_of relationship.