The Impact of Spelling Errors on Patent Search

Proceedings of the 13th Conference of the European Chapter of the Association for Computational Linguistics, pages 570–579, Avignon, France, April 23 - 27 2012. c⃝2012 Association for Computational Linguistics The Impact of Spelling Errors on Patent Search Benno Stein and Dennis Hoppe and Tim Gollub Bauhaus-Universität Weimar 99421 Weimar, Germany <first name>.<last name>@uni-weimar.de Abstract The search in patent databases is a risky business compared to the search in other domains. A single document that is relevant but overlooked during a patent search can turn into an expensive proposition. While recent research engages in specialized mod- els and algorithms to improve the effective- ness of patent retrieval, we bring another aspect into focus: the detection and ex- ploitation of patent inconsistencies. In par- ticular, we analyze spelling errors in the as- signee field of patents granted by the United States Patent & Trademark Office. We in- troduce technology in order to improve re- trieval effectiveness despite the presence of typographical ambiguities. In this regard, we (1) quantify spelling errors in terms of edit distance and phonological dissimilarity and (2) render error detection as a learn- ing problem that combines word dissimi- larities with patent meta-features. For the task of finding all patents of a company, our approach improves recall from 96.7% (when using a state-of-the-art patent search engine) to 99.5%, while precision is com- promised by only 3.7%. 1 Introduction Patent search forms the heart of most retrieval tasks in the intellectual property domain—cf. Ta- ble 1, which provides an overview of various user groups along with their typical (•) and related (◦) tasks. The due diligence task, for example, is concerned with legal issues that arise while inves- tigating another company. Part of an investiga- tion is a patent portfolio comparison between one or more competitors (Lupu et al., 2011). Within all tasks recall is preferred over precision, a fact which distinguishes patent search from general web search. This retrieval constraint has produced a variety of sophisticated approaches tailored to the patent domain: citation analysis (Magdy and Jones, 2010), the learning of section-specific re- trieval models (Lopez and Romary, 2010), and au- tomated query generation (Xue and Croft, 2009). Each approach improves retrieval performance, but what keeps them from attaining maximum ef- fectiveness in terms of recall are the inconsisten- cies found in patents: incomplete citation sets, in- correctly assigned classification codes, and, not least, spelling errors. Our paper deals with spelling errors in an oblig- atory and important field of each patent, namely, the patent assignee name. Bibliographic fields are widely used among professional patent searchers in order to constrain keyword-based search ses- sions (Joho et al., 2010). The assignee name is particularly helpful for patentability searches and portfolio analyses since it determines the com- pany holding the patent. Patent experts address these search tasks by formulating queries contain- ing the company name in question, in the hope of finding all patents owned by that company. A for- mal and more precise description of this relevant search task is …

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