***Special Issue "Query Answering in Big Data Analytics: Models, Tools, Trends and Challenges"*** A special issue of Information (ISSN 2078-2489). This special issue belongs to the section "Information Processes". https://www.mdpi.com/journal/information/special_issues/Query_Answering_Big_Data ***Extended Deadline*** Manuscript submission deadline: 15 June 2021 Nowadays, the continuous evolution of products and services is generating a huge volume and variety of data at a high velocity. In many high-performance applications, which lead to the generation of a vast amount of structured, semi-structured, and unstructured data referred to as big data, timely and cost-effective analytics become a key element for advancement in various scientific, business, and engineering disciplines. In the context of different analytical tasks, the problem of query answering still represents an active research area due to the growing number of users and the increasing amount of data. It encompasses the definition, the efficient execution and the logical and physical optimization of analytical queries. However, new techniques with significant potential for innovation have to be elaborated to effectively manage and access the vast amount of data for analytical applications to support reliable decision making. The purpose of this Special Issue is to present the latest developments in models and tools as well as the trends and challenges related to query answering in big data analytics. Investigators in the field are invited to contribute by providing their original, unpublished works. Both research and review papers are welcome. Topics of interest include but are not limited to: Data science and big data Stream data analysis, representation and management Business analytics Approximation models, methods and algorithms Query languages, user interfaces and data visualization Datalog, recursive, and logical query answering Link and graph mining Web and mobile analytics Text and multimedia analytics Systems, architectures, platforms Applications to Different Sectors: Business intelligence Energy and finance Healthcare and welfare Privacy and security Transportation Risk management Guest Editors: Dr. Elaheh Pourabbas, National Rsesearch Council (CNR) of Italy (firstname.lastname@example.org) Manuscript Submission Information: Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website. Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Information is an international peer-reviewed open access monthly journal published by MDPI. Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions. NOTE: The first ten submitted paper can get 200CHF discount. If you want to use the discount, please contact < email@example.com> to apply.