Showing papers by "Wang-Chien Lee published in 2001"

System and method for automatic loading of an xml document defined by a document-type definition into a relational database including the generation of a relational schema therefor

Abstract: A system and a method are provided for generating (28) a schema (22) for a relational database corresponding to a document having a document-type definition (18) and data complying with the document-type definition (18). The document-type definition (18) has content particles representative of the structure of the document data including one or more of the following content particles: elements, attributes of elements, nesting relationships between elements, grouping relationships between elements, schema (22) ordering indicators, existence indicators, occurrence indicators and element ID referencing indicators. The system and method described herein also contemplates loading the data into the relational database in a manner consistent with the relational schema (22). Metadata is extracting from the document-type definition (18) representative of the document-type definition (18). The schema (22) for the relational database is generated from the metadata, wherein at least one table is thereby defined in the relational database corresponding to at least one content particle of the document-type definition (18) via the metadata (34). The data is then loaded into the at least one table of the relational database according to the relational schema (22) in a manner driven by the metadata (34).

System and method for synchronizing and/or updating an existing relational database with supplemental XML data

Abstract: A system and a method for synchronizing and updating a relational database with supplemental data in which the relational database has a set of tables defined by a relational schema. The supplemental data preferably comprises data in a tagged format having a document-type definition representative of the relational schema and is represented in a document object. The system and method preferably ensure record-by-record updating and synchronization of the relational database with the at least one proposed data update by receiving at least one proposed data update from a source external to the relational database; and propagating the received at least one proposed data update into the relational database. In this matter, the compliance with both the relational database relational schema and the tagged data document type definition is ensured without requiring reloading existing data in the relational database.

A Hybrid Index Technique for Power Efficient Data Broadcast

Abstract: The intention of power conservative indexing techniques for wireless data broadcast is to reduce mobile client tune-in time while maintaining an acceptable data access time. In this paper, we investigate indexing techniques based on index trees and signatures for data disseminated on a broadcast channel. Moreover, a hybrid indexing method combining strengths of the signature and the index tree techniques is proposed. Different from previous studies, our research takes into consideration of two important data organization factors, namely, clustering and scheduling. Cost models for the three indexing methods are derived for various data organization accommodating these two factors. Based on our analytical comparisons, the signature and the hybrid indexing techniques are the best choices for power conservative indexing of various data organization on wireless broadcast channels.

An overview of pervasive computing

Abstract: he importance of pervasive computing is rapidlyincreasingwith the current trend toward universal presence of mobile computing, computer networks, and wireless communications ineveryday life. In thelastdecade, there has been a dramatic increase in the use of companion devices and embedded computing devices. For example, wirelessly connectcd organizers and smart phones are becoming popular, and digital computing in some form is now an integral part of numerous evcryday appliances. This has led to a change in thc waywe perceive computing andcomputers. Computers are no longer standalone special-purpose machines to beusedbyexperts; rather, they arc ubiquitously present in a networked environment to scrve myriad needs of everyday life. The change in our perception of computing and computing devices, and their ever increasing presence in our everyday life is the subject of the new ficld known as pervasive computing. The word pervasive

Clock: synchronizing internal relational storage with external XML documents

Abstract: In many business settings, a relational database system (RDBMS) will serve as the storage manager for data from XML documents. In such a system, once the XML data is dissembled and loaded into the storage system, XML queries posed against the (virtual) XML documents are processed by translating them into SQL queries against the relational storage. However, for applications which frequently update their XML documents, we cannot afford to reload a complete, possibly large, document for each update, instead we must be able to incrementally propagate document updates to the stored XML data. We address the issue of correctly reflecting updates of external XML documents into the loaded XML data in a relational database system. We describe Clock, a framework for synchronizing the relational storage with updated XML documents by exploiting a metadata-driven technology. First, we propose a set of (DTD preserving) update primitives for XML documents. Second, based on the mapping between XML and the relational model, we describe the propagation of those update primitives. Validation of the updates ensures they will not violate the constraints specified by the DTD. We have implemented a working prototype of the Clock system using the IBM's XML4J parser JDBC 2 and Oracle 81. We report on preliminary experiments conducted using this prototype to analyze our algorithms in a document update setting.

An optimal cache replacement policy for wireless data dissemination under cache consistency

Abstract: A good cache management method for mobile wireless environments has to handle problems associated with limited client resources and frequent client disconnections, in addition to standard problems found in wired environments, such as variable data sizes and data updates. In this paper we propose a gain-based cache replacement policy, Min-SAUD, for wireless data dissemination when cache consistency must be enforced before a cached item is used. Min-SAUD considers several factors that affect cache performance, namely access probability, update frequency, data size, retrieval delay, and cache validation cost. Min-SAUD is optimal in terms of the stretch performance measure. Preliminary experimental results show that in most cases the Min-SAUD replacement policy substantially outperforms two existing policies, namely LRU and SAIU.

Indexing techniques for power management in multi-attribute data broadcast

Abstract: In this paper, we discuss the power conservative indexing techniques for managing multi-attribute data broadcast on wireless channels. These indexing techniques, namely, index tree, signature and hybrid, aim at improving the battery power consumption of mobile clients. By taking into account the broadcast management factors such as clustering and scheduling, these three indexing schemes may significantly reduce tune-in time while maintaining a reasonable access time. Cost models for single and multi-attribute query processing are developed. Our performance evaluation shows that the signature and hybrid methods are superior to the index tree method.

Sangam - a solution to support multiple data models, their mappings and maintenance

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Power conserving and access efficient indexes for wireless computing

Abstract: In this paper, we introduce our research on power conserving and access efficient indexing techniques for wireless computing and revisit some of the pioneering work in this area. These indexing methods show that battery power consumption in mobile clients can be significantly reduced with some access time overhead. Among them, hybrid index is the best choice for improving power efficiency under both scenarios of single and multiple attributes based queries. Moreover, we introduce two access efficient indexing methods, cache schedule and integrated signature, for a wireless data dissemination system that incorporates both of broadcast and on-demand services.