International conference on web information systems engineering (WISE) has established itself as a community aiming at high quality research and offering the ground for advancing efforts in topics related to Web information systems. Previous WISE conferences were held in Hong Kong, China (2000), Kyoto, Japan (2001), Singapore (2002), Roma, Italy (2003), Brisbane, Australia (2004), New York, USA (2005), Wuhan, China (2006), Nancy, France (2007), Auckland, New Zealand (2008), Poznan, Poland (2009), Hong Kong, China (2010), Sydney, Australia (2011), Paphos, Cyprus (2012), Nanjing, China (2013), Thessaloniki, Greece (2014), Miami, USA (2015), Shanghai, China (2016), Puschino, Russia (2017), Dubai, UAE (2018), Hong Kong (2019), and Amsterdam and Leiden, Netherlands (2020). WISE 2021 will be held in Melbourne, Australia, 26-29, 2021. http://www.wise-conferences.org/2021/ We invite submissions of papers for the main conference proceedings of WISE 2021. All papers will be reviewed in a double-blind process and accepted papers will be presented at the conference. Topics of interest include but not limited to: Web-scale Distributed and Cloud Computing Recommender Systems Deep/Hidden Web Clickstream Analytics Rich Web UI and HCI Semantic Web Machine Learning for the Web Linked Open Data Human Factors and Social Issues Web Big Data Techniques and Mining Social Web Models and Analysis Web Agents and Web Intelligence Web Data Models Web Information Retrieval and Text Analytics Web Metrics and Performance Web Mining and Web Warehousing Web Security and Trust Management Web-based Business Processes and Web Services Web Tools and Visualization Data Science and AI technology Web-based Applications (e.g., Auction and Negotiation, e-Commerce, e-Government, e-Learning, etc.) Important Dates: Abstract Submission Deadline: June 24, 2021 Full Paper Submission Deadline: July 1, 2021