However, about two out of three MeSH terms from this path were relevant. Half of the source concepts reaching this path were isolated adjectives, simply linked to their corresponding MeSH nominal equivalent. It appears that non relevant MeSH terms often come from a unique path in the graph built from children or siblings. This can occur when only one of the concepts from the seed of the graph has MeSH ancestors. In this case, only one part of the semantics is emphasized, which is not necessarily common to the source concept.
Methods relying on semantic principles assume that all the relationships are expressed.
A certain lack of relationships has already been identified in other studies. Two concepts close in meaning may not be mapped to the same MeSH terms. As noted in other studies, inconsistencies in the categorization of the concepts are a source of failures in methods relying on semantics. Specificity can be increased by allowing the graph of ancestors to be built only from the source concept itself and not from its children or siblings. Not using the RO concepts can also help limit the percentage of non relevant MeSH terms.