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.

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Session I: Wireless Networks and Communications.- Wireless VoIP: Opportunities and Challenges.- GSM Mobile Phone Based Communication of Multimedia Information: A Case Study.- A Witness-Aided Routing Protocol for Mobile Ad-Hoc Networks with Unidirectional Links.- Assessing Opportunities for Broadband Optical Wireless Local Loops in an Unbundled Access Network.- On Simulation Modeling of Information Dissemination Systems in Mobile Environments.- Session II: Transaction Processing in Mobile Environments.- On the Performance of Transaction Processing in Broadcast Environments.- Transaction Processing in an Asymmetric Mobile Environment.- Speculative Lock Management to Increase Concurrency in Mobile Environments.- Optimistic Concurrency Control in Broadcast Environments: Looking Forward at the Server and Backward at the Clients.- Session III: Ubiquitous Information Services.- Modelling the WAP Transaction Service Using Coloured Petri Nets.- Enabling Ubiquitous Database Access with XML.- Design and Evaluation of an Information Announcement Mechanism for Mobile Computers.- Active Rule System for Adaptive Mobile Data Access.- Preserving Smooth Traffic and High Presentation QoS for VBR-Encoded Video.- Session IV: Mobile Data Replication and Caching.- Peer Replication with Selective Control.- Cache Coherency in Location-Dependent Information Services for Mobile Environment.- An Autonomous Data Coherency Protocol for Mobile Devices.- Session V: Mobility and Location Management.- Location Management Strategies for Reducing Both Movement Cost and Locating Cost Simultaneously.- Internet Mobility Support Optimized for Client Access and Its Scalable Authentication Framework.- Proxy Agent Consistency Service Based on CORBA.- Keynote Speeches.- Integrating Mobile Objects into the Wirelessly Wired World: The Need for Energy Efficient Algorithms.- Databases Unplugged: Challenges in Ubiquitous Data Management.