With the rapid development in wireless-network and portable computing and communication devices, mobile users are expected to have access to information from anywhere at anytime in the near future, in the form of ubiquitous c- puting, a term coined by the late Mark Weiser of Xerox, PARC. Indeed, the emerging mobile technology will probably bring us the next wave of information revolution and change our society as we move into the next millennium. Before this vision can be realized, a number of challenges have to be overcome. Tra- tionally, network-based information systems have been developed under wired assumptions about the connectivity and topology of the underlying networks. To eliminate these limitations from wireless and mobile environments, research e orts are needed in networks, architecture, software infrastructure, and app- cation levels, in order to provide mobile data access over hybrid wireless and wired networks, which is the central theme of this conference. Theseproceedingscollectthetechnicalpapersselectedforpresentationatthe First International Conference on Mobile Data Access (MDA'99), held in Hong Kong, followingits returnto China, on December 16{17,1999.Theconferenceis heldin conjunctionwith the InternationalComputer Science Conference, the - ternational Conference on Real-time Computing Systems and Applications, and the Paci c Rim International Symposium on Dependable Computing, forming part of the International Computer Congress.

The three-volume set LNCS 12681-12683 constitutes the proceedings of the 26th International Conference on Database Systems for Advanced Applications, DASFAA 2021, held in Taipei, Taiwan, in April 2021. The total of 156 papers presented in this three-volume set was carefully reviewed and selected from 490 submissions. The topic areas for the selected papers include information retrieval, search and recommendation techniques; RDF, knowledge graphs, semantic web, and knowledge management; and spatial, temporal, sequence, and streaming data management, while the dominant keywords are network, recommendation, graph, learning, and model. These topic areas and keywords shed the light on the direction where the research in DASFAA is moving towards. Due to the Corona pandemic this event was held virtually.

The three-volume set LNCS 12681-12683 constitutes the proceedings of the 26th International Conference on Database Systems for Advanced Applications, DASFAA 2021, held in Taipei, Taiwan, in April 2021. The total of 156 papers presented in this three-volume set was carefully reviewed and selected from 490 submissions. The topic areas for the selected papers include information retrieval, search and recommendation techniques; RDF, knowledge graphs, semantic web, and knowledge management; and spatial, temporal, sequence, and streaming data management, while the dominant keywords are network, recommendation, graph, learning, and model. These topic areas and keywords shed the light on the direction where the research in DASFAA is moving towards. Due to the Corona pandemic this event was held virtually.

The three-volume set LNCS 12681-12683 constitutes the proceedings of the 26th International Conference on Database Systems for Advanced Applications, DASFAA 2021, held in Taipei, Taiwan, in April 2021. The total of 156 papers presented in this three-volume set was carefully reviewed and selected from 490 submissions. The topic areas for the selected papers include information retrieval, search and recommendation techniques; RDF, knowledge graphs, semantic web, and knowledge management; and spatial, temporal, sequence, and streaming data management, while the dominant keywords are network, recommendation, graph, learning, and model. These topic areas and keywords shed the light on the direction where the research in DASFAA is moving towards. Due to the Corona pandemic this event was held virtually.