Extracting Schema Knowledge from Text Documents: Part I. Problem Formulation and Method Overview

— This article discusses the importance of automatic schema knowledge extraction for natural language processing. A broad overview of methods of and approaches to describing and extracting schemas is given; theoretical approaches to formalizing schemas are considered. Some problems that involve knowledge on the schema structure of texts are listed. Popular approaches to automatic schema knowledge extraction and quality control methods for these approaches are presented. A list of open corpora that can be used for schema extraction, some of which are created specifically for this purpose and some are universal, is provided.