Mathematical modeling of formula images for their recognition

The work is devoted to the use of the basic elements of graph theory to solve the mathematical formula recognition problem. We introduce the concepts of two-level graphs and two-dimensional oriented graphs that make it possible to describe complex images consisting of the hierarchy of parts with a particular relative position. We consider a special function that builds a two-dimensional oriented graph from a mathematical formula; the graph is called a graph of mathematical expression image. The mapping rules for basic classes of mathematical formulae are presented. We describe a problem-solving procedure for a recognition problem, which is based on the reverse problem of constructing of a mathematical-expression image graph.