6530554
Adaptive Index Utilization in Memory-Resident Structural Joins
We consider adaptive index utilization as a fine-grained problem in autonomic databases in which an existing index is dynamically determined to be used or not in query processing. As a special case, we study this problem for structural joins, the core operator in XML query processing, in the main memory. We find that index utilization is beneficial for structural joins only under certain join selectivity and distribution of matching elements. Therefore, we propose adaptive algorithms to decide whether to use an index probe or a data scan for each step of matching during the processing of a structural join operator. Our adaptive algorithms are based on the history, the look-ahead information, or both. We have developed a cost model to facilitate this adaptation and have conducted experiments with both synthetic and real-world data sets. Our results show that adaptively utilizing indexes in a structural join improves the performance by taking advantage of both sequential scans and index probes.
15301775
Implementing Xquery 1.0: The Galax Experience
Galax is a light-weight, portable, open-source implementation of XQuery 1.0. Started in December 2000 as a small prototype designed to test the XQuery static type system, Galax has now become a solid implementation, aiming at full conformance with the family of XQuery 1.0 specifications. Because of its completeness and open architecture, Galax also turns out to be a very convenient platform for researchers interested in experimenting with XQuery optimization. 
 
We demonstrate the Galax system as well as its most advanced features, including support for XPath 2.0, XML Schema and static type-checking. We also present some of our first experiments with optimization. Notably, we demonstrate query rewriting capabilities in the Galax compiler, and the ability to run queries on documents up to a Gigabyte without the need for preindexing. Although early versions of Galax have been shown in industrial conferences over the last two years, this is the first time it is demonstrated in the database community.
17095732
Incremental evaluation of schema-directed XML publishing
When large XML documents published from a database are maintained externally, it is inefficient to repeatedly recompute them when the database is updated. Vastly preferable is incremental update, as common for views stored in a data warehouse. However, to support schema-directed publishing, there may be no simple query that defines the mapping from the database to the external document. To meet the need for efficient incremental update, this paper studies two approaches for incremental evaluation of ATGs [4], a formalism for schema-directed XML publishing. The reduction approach seeks to push as much work as possible to the underlying DBMS. It is based on a relational encoding of XML trees and a nontrivial translation of ATGs to SQL 99 queries with recursion. However, a weakness of this approach is that it relies on high-end DBMS features rather than the lowest common denominator. In contrast, the bud-cut approach pushes only simple queries to the DBNS and performs the bulk of the work in middleware. It capitalizes on the tree-structure of XML views to minimize unnecessary recomputations and leverages optimization techniques developed for XML publishing. While implementation of the reduction approach is not yet in the reach of commercial DBMS, we have implemented the bud-cut approach and experimentally evaluated its performance compared to recomputation.
3203090
What are real DTDs like?
DTDs have proved important in a variety of areas: transformations between XML and databases, XML storage, XML publishing, consistency analysis of XML specifications, typechecking, and optimization of XML queries. Much of this work depends on certain assumptions about DTDs, e.g., the absence of recursion and non-determinism. With this comes the need to justify these assumptions against DTDs in the real world. This paper surveys a number of DTDs collected from the Web, and provides statistics with respect to a variety of criteria commonly discussed in XML resesarch.
10441527
Efficient Support for Ordered XPath Processing in Tree-Unaware Commercial Relational Databases
In this paper, we present a novel ordered XPATH evaluation in treeunaware RDBMS. The novelties of our approach lies in the followings. (a) We propose a novel XML storage scheme which comprises only leaf nodes, their corresponding data values, order encodings and their root-to-leaf paths. (b) We propose an algorithm for mapping ordered XPATH queries into SQL queries over the storage scheme. (c) We propose an optimization technique that enforces all mapped SQL queries to be evaluated in a "left-to-right" join order. By employing these techniques, we show, through a comprehensive experiment, that our approach not only scales well but also performs better than some representative tree-unaware approaches on more than 65% of our benchmark queries with the highest observed gain factor being 1939. In addition, our approach reduces significantly the performance gap between tree-aware and tree-unaware approaches and even outperforms a state-of-the-art tree-aware approach for certain benchmark queries.
2642886
Cache-Conscious Automata for XML Filtering
Hardware cache behavior is an important factor in the performance of memory-resident, data-intensive systems such as XML filtering engines. A key data structure in several recent XML filters is the automaton, which is used to represent the long-running XML queries in the main memory. In this paper, we study the cache performance of automaton-based XML filtering through analytical modeling and system measurement. Furthermore, we propose a cache-conscious automaton organization technique, called the hot buffer, to improve the locality of automaton state transitions. Our results show that 1) our cache performance model for XML filtering automata is highly accurate and 2) the hot buffer improves the cache performance as well as the overall performance of automaton-based XML filtering
11850990
Network Traffic Reduction by Hypertext Compression
This paper proposes a three-step process to reduce the size of hypertext documents for reducing the network traffic on the Internet. With the explosive growth in the number of users on the Internet, the bandwidth demand has grown tremendously. Before the improvement of network infrastructures can meet the demand, this paper addresses the problem by reducing the size of HTML documents that currently occupies majority of the network traffic on the Internet. The proposed process consists of three steps: (1) shrinking HTML documents by removing data that will not alter the appearance and the function, (2) encoding HTML documents by representing most frequent used tags and words with single bytes, and (3) compressing HTML documents by using standard compression utilities. Our test results show that the proposed process achieves a reduction ratio of 81% on average. We also developed a browser plug-in program that provides transparent access for the users when viewing the reduced-size HTML documents. With the plug-in program, the users will not see any differences when viewing the reduced-sized HTML documents comparing to the original ones. They will, however, experience a reduction in retrieval latency on average of 15%.
8402297
The Effects of Users' Motivation on their Perception to Trading Systems of Digital Content Accessories: Focusing on Trading Items in Online Games
As the market for digital content accessories grows, motivation for trading digital content accessories has significant effects on their fun, transaction cost, and intention to trade and use digital contents. However, few empirical studies have investigated users' perception of trading digital content accessories. The main purpose of this study is to construct and verify a research model identifying the relationships among the attributes of transaction, users' perceived fun and transaction cost, and the intention to trade and use digital contents, all of which are modulated by users' motivation. The research model was constructed based on transaction cost theory and motivational theory. An experiment in a real massive multiplayer online role playing game (MMORPG) environment was conducted and the results indicate that users' different motivations have effects on their perception to digital content accessories trading systems, intention to use those systems, and intention to use digital contents
38524318
Making Sense of Search Results by Automatic Web-page Classifications
This paper reports the development of a system for automatically organizing Internet web pages into meaningful categories. The aim of the system is to allow Internet users to find useful information in less time. The current problem with using the Internet is how to find the information that we need. With the explosive growth in the Internet, the information overload situation is getting worse. The proposed system automatically classifies web pages based on three types of information: (1) The system analyzes organizational information among web pages (inter-web-page relationship), such as an URL and links within a web page. (2) It analyzes the meta-web-page information such as data contained in META tags and formatting data of a web page. And (3), it analyzes web-page-content information such as keywords and phrases in the content of a web page. Our results show that combining all three types of information provides better accuracy.
6632676
Applying Semantic Links for Classifying Web Pages
Automatic hypertext classification is an essential technique for organizing vast amount of Internet Web pages or HTML documents. One the of problems in classifying Web pages is that Web pages are usually short and contain insufficient text to clearly identify its category. Text classification mechanisms, by analyzing only the contents of the document itself, are relatively ineffective in classifying short Web pages. This paper proposes a new hypertext classification mechanism to address the problem by analyzing not only the Web page itself but also its linked Web pages referred by the URLs contained within the page. The URLs are treated as semantic links. The hypothesis is that the linked Web pages contain related information to help identifying the category of the Web page. Experimental results show that the proposed approach could increase the accuracy by 35% over the approach of analyzing only the Web page itself.
9581771
Scalable QoS guaranteed communication services for real-time applications
We propose an approach to flow-unaware admission control which is a combination with an aggregate packet forwarding scheme, improving scalability of networks while guaranteeing end-to-end deadlines for real-time applications. We achieve this by using an off-line delay computation and verification step, which allows to reduce the overhead at admission control while keeping admission probability and resource utilization high. Our evaluation data show that our system's admission probabilities are very close to those of significantly more expensive flow-aware approaches. At the same time, the admission control overhead during flow establishment is very low. Our results therefore support the claim from the DS architecture literature that scalability can be achieved through flow aggregation without sacrificing resource utilization and with significant reduction in run time overhead.