This book constitutes the refereed proceedings of the 44th German Conference on Artificial Intelligence, KI 2021, held in September/October 2021. Due to COVID-19 pandemic the conference was held virtually. The 16 full and 4 short papers with one extended abstract were carefully reviewed and selected from 59 submissions. As well-established annual conference series KI is dedicated to research on theory and applications across all methods and topic areas of AI research.

This work investigates the quantifier elimination problem in real closed fields with respect to the application in description logics. The motivation for the investigation in this topic is mainly based on the demand for an extension of description logic systems to support a default concrete domain for non-linear multivariate equations and inequations. The authors provide a literature overview that summarizes main mathematical tools for checking whether a set of non-linear multivariate (in-)equatins is satisfiable (quantifier elimination problem). The authors shortly describe how application examples are handled with a prototype implementation.