Table 1.

Comparative analysis MeSH vs. IPC. The hierarchical structures are similar, but MeSH terms are shorter and more likely to occur in text. The number of MeSH annotations per document far surpasses the number of classes per patent.

Property	MeSH	IPC
number of hierarchy entries	54095	69487
number of unique entries	26581	69487
number of hierarchy levels	13	14
average string length main labels/class definitions	18	50
string length longest main label/class definition	104	596
string length shortest main label/class definition	2	3
average number of synonyms	8	0
occurrence of class labels in text	frequent	very rare
average number of annotations per document	9	2
number of unique annotations	25646	56599
proportion of documents with multiple annotations	86%	53%
proportion of documents with related annotations (same hierarchy tree)	81%	46%