Full Text Formula Search in zbMATH

[摘要] Three years ago, formula search has been introduced inzbMATH1. Formula retrieval is based on three ingredients: digitisation, content extraction, and a math-awaresearch engine. Our aim is to give an update on its statusand developments.The search uses the MathWebSearch engine2 developed by the KWARC group3 at Jacobs UniversityBremen, which leverages a technique called substitutiontree indexing4. This method enables high-performancestructural searching in a large corpus of formulae using query expressions that may contain free variables orplaceholders. The latter are denoted by a leading question mark and will match arbitrary subexpressions of anycomplexity. When occurring multiple times in the inputquery, they will be substituted with the same concrete expression for each occurrence. Thus a query like “-?a \leq?b \leq ?a” would match the formula “−a≤f(u)≤a”,but not “0≤x≤1”.