Optical formula recognition

The paper describes the design and the first steps of implementation of OFR (optical formula recognition), a system for extracting and understanding mathematical expressions in printed documents. Our approach clearly separate OCR step, geometrical treatments and syntactic analysis. We focus on the third part: we define a class of context sensitive graph grammars for mathematical formulas, study their properties and show how to remove their ambiguities (by adding contexts in rules) to define efficient parsing. This method is based on a “critical pairs” approach in the sense of Knuth-Bendix algorithm