Showing papers by "Wang-Chien Lee published in 1998"

Path dictionary: a new access method for query processing in object-oriented databases

Abstract: We present a new access method, called the path dictionary index (PDI) method, for supporting nested queries on object-oriented databases. PDI supports object traversal and associative search, respectively, with a path dictionary and a set of attribute indexes built on top of the path dictionary. We discuss issues on indexing and query processing in object-oriented databases; describe the operations of the new mechanism; develop cost models for its storage overhead and query and update costs; and compare the new mechanism to the path index method. The result shows that the path dictionary index method is significantly better than the path index method over a wide range of parameters in terms of retrieval and update costs and that the storage overhead grows slowly with the number of indexed attributes.

Optimal channel allocation for data dissemination in mobile computing environments

Abstract: We discuss the wireless channel allocation problem for data dissemination in mobile computing systems. Methods for accessing data through broadcast and on-demand channels are described. We provide analytical models and cost formulae for the exclusive broadcast channels and the exclusive on-demand channels and propose a dynamic channel allocation algorithm for optimizing system performance. Our performance evaluation shows that dynamic channel allocation significantly improves system performance and the channel allocation algorithm gives us the optimal solution for various system parameter settings.

Dynamic Data Delivery in Wireless Communication Environments

Abstract: Information broadcasting, caching of frequently accessed data, and pull-based data delivery are commonly used techniques to reduce data access time of wireless information services. Most of the studies in the literature focused either on individual technique or a combination of them with some restrictive assumptions. In this paper, we propose a dynamic data delivery model where these three techniques work together in an integrated manner. A particular feature of our model is that data are disseminated through various storage mediums according to the dynamically collected data access patterns. Performance evaluation of the model is conducted by simulation studies.

A comparison of indexing methods for data broadcast on the air

Abstract: Several indexing techniques for data broadcast on the air have been proposed for power conservation on mobile computers in the past few years. Indexing techniques for broadcast channels can save battery power (estimated by tune-in time) while incurring only limited overhead on access time. In this paper we compare indexing techniques based on the index tree and the signature methods and find that both methods prevail under different circumstances.

A framework for TMN-CORBA interoperability

Abstract: The Telecommunications Management Network (TMN) Architecture model is the de facto standard for the telecommunications industry; it plays an influential role in development of telecommunications-related systems. On the other hand, the Common Object Request Broker Architecture (CORBA) model, aimed at the development and integration of distributed systems, has matured and gained importance over the past few years and thus will be influential in the development of general application systems. In this paper, we study the interoperability issues between systems based on these models because of their relevance to integrated telecommunications enterprises. For example, billing can require interactions between OSI-based systems supporting usage measurement and CORBA-based systems managing customer profiles and financial activities. We first introduce a framework for comparing different architectures. This framework identifies key characteristics of architectural models as well as areas where inter-model mappings may be required. We examine the TMN and CORBA models in the context of this framework, then explore some of the issues in providing interoperability between TMN-based and CORBA-based systems. This exploration is guided by the the framework comparison points. Finally, we conclude the paper with a discussion of future work.

Summary of Panel Discussion: Future of Mobile Computing - Convergence of Research and Applications

Abstract: In the panel discussion session of International Workshop on Mobile Data Access, an enthusiastic audience was invited to join the panel of experts, Prof Dik Lun Lee (Hong Kong University of Science and Technology, Hong Kong), Dr Radhakrishna Pillai (Kent Ridge Digital Labs, Singapore), Dr Hiroki Takakura (Kyoto University, Japan) and Mr Stuart Jacobs (GTE Laboratories, USA) to explore several important issues relating to the data access aspect of mobile computing

Indexing Techniques for Data Broadcast on Wireless Channelsrmulti.

Abstract: Indexing techniques have been developed as a means for clients to reduce power consumption and to select between broadcast and on demand data services In this paper we provide an overview of our research on indexing techniques and revisit some related work in the literature Our study incorporates two important techniques clustering and scheduling for improving data broadcast e ciency and explores the scenarios of single and multiple attribute query processing Moreover we apply two indexing methods cache schedule and integrated signature to a hierarchical data delivery