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Component

In general, a component-of a component-of a whole is a kind of component-of the whole. Thus, the component-of semantic link is fully transitive. However, difficulties arise when considering the inheritance of other, non-partitive semantic links across the component-of link.

Functions of substructures appear to be inheritable along component-of links: the functions of the whole includes the sum of the functions of the components. For example, the pancreas is a kind of structure that secretes insulin, even though this function is actually fulfilled by identifiable and discrete components within the pancreas, the Islets of Langerhans. But inheritance of function-of across component-of is only valid up to a certain (often arbitrary) level of anatomical aggregation: the gastrointestinal system as a whole is not considered to be a kind of structure that secretes insulin, even though the pancreas is a component of it. By contrast, abnormality of gastric secretion (e.g. achlorhydria) is a kind of functional gastrointestinal disorder, but thyroid hypersecretion is not a disorder of neck function.

We capture this variable inheritance by preventing inheritance of function-of across component-of itself but enabling it for a child link of component-of: func-component-of. Under this scheme, the Islets of Langerhans are func-component-of the pancreas but the pancreas is only a component-of the gastrointestinal tract. Conversely, the stomach is a full func-component-of the gastrointestinal tract.

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