A study of approaches to answering complex questions over knowledge bases

摘要

Question answering (QA) systems retrieve the most relevant answer to a natural language question. Knowledge base question answering (KBQA) systems explore entities and relations from knowledge bases to generate answers. Currently, QA systems achieve better results when answering simple questions, but complex QA systems are receiving great attention nowadays. However, there is a lack of studies that analyzes complex questions inside the KBQA field and how it has been addressed. This work aims to fill this gap, presenting a systematic mapping on the complex knowledge base question answering (C-KBQA). The main contributions of this work are: (i) the use of a systematic method to provide an overview of C-KBQA; (ii) a collection of 54 papers systematically selected from 894 papers; (iii) the identification of the most frequent venues, domains, and knowledge bases used in the literature; (iv) a mapping of methods, datasets, and metrics used in the C-KBQA scenario; (v) future directions and the main gaps in the C-KBQA field. The authors show that the C-KBQA system aims to solve two question types: multi-hop and constraint questions. Also, it was possible to identify three main steps to construct a C-KBQA system and the use of two main approaches in this process. It was also noticed that datasets for C-KBQA are still an open challenge.