Extracting complexity metrics of technological artifacts and systems from patents using patent document structure

Abstract

This study investigates the relationship between different complexity metrics from the literature and metadata fields in patents. Patent citations, claims and other fields are compared against complexity metrics derived from the number of parts and part interactions, as extracted from over 100 000 patents. A method is proposed to extract part descriptions from patents by leveraging the XML structure of the patent publication. The part names are used in a normalisation process to gain an accurate count of unique parts in a patent. A commonly used metric for complexity, specifically derived from patents, is analysed and tested against complexity measures derived from the amount of parts and interactions in a patent. The study underlines several shortcomings in the measurement of complexity in patents, especially the literature's propensity to use sub-class classifications from patent classification hierarchies as proxies for the complexity of different technology types. Furthermore, it is demonstrated that derivations from data fields of patents, including citation and claim counts, are positively correlated with the complexity of the patented invention.