Junho Shim

Proxy cache algorithms: design, implementation, and performance

Caching at proxy servers is one of the ways to reduce the response time perceived by World Wide Web users. Cache replacement algorithms play a central role in the response time reduction by selecting a subset of documents for caching, so that a given performance metric is maximized. At the same time, the cache must take extra steps to guarantee some form of consistency of the cached documents. Cache consistency algorithms enforce appropriate guarantees about the staleness of the cached documents. We describe a unified cache maintenance algorithm, LNC-R-WS-U, which integrates both cache replacement and consistency algorithms. The LNC-R-WS-U algorithm evicts documents from the cache based on the delay to fetch each document into the cache. Consequently, the documents that took a long time to fetch are preferentially kept in the cache. The LNC-R-W3-U algorithm also considers in the eviction consideration the validation rate of each document, as provided by the cache consistency component of LNC-R-WS-U. Consequently, documents that are infrequently updated and thus seldom require validations are preferentially retained in the cache. We describe the implementation of LNC-R-W3-U and its integration with the Apache 1.2.6 code base. Finally, we present a trace-driven experimental study of LNC-R-W3-U performance and its comparison with other previously published algorithms for cache maintenance.

A case for delay-conscious caching of Web documents

Caching at proxy servers plays an important role in reducing the latency of the user response, the network delays and the load on Web servers. The cache performance depends critically on the design of the cache replacement algorithm. Unfortunately, most cache replacement algorithms ignore the Webs scale. In this paper we argue for the design of delay-conscious cache replacement algorithms which explicitly consider the Webs scale by preferentially caching documents which require a long time to fetch to the cache. We present a new, delay-conscious cache replacement algorithm LNC-R-W3 which maximizes a performance metric called delay-savings-ratio. Subsequently, we test the performance of LNC-R-W3 experimentally and compare it with the performance of other existing cache replacement algorithms, namely LRU and LRU-MIN.

Building an operational product ontology system

A base of clearly defined product information is a key foundation for an e-commerce system. The manipulation and exchange of semantically enriched and precise product information can enhance the quality of an e-commerce system and offer a high level of interoperability with other systems. Product information consists of product attributes and the relationships between products. Product categorization (or classification) is one type of such relationships. Ontology can play an important role in the formalization of product information. Although the idea of utilizing ontology for e-Catalogs has been raised before, we are yet to find an operational implementation of applying ontology in the domain. In this paper, we report on our recent effort to build an operational product ontology system for a government procurement service. The system is designed to serve as a product ontology knowledge base; not only for the design and construction of product databases but also for search and discovery of products. Especially, the keyword-based searching over product ontology database demands different techniques from those over conventional document databases or relational databases, and should be designed to reflect particular characteristics of product ontology. We also introduce some other issues that we have experienced in the project, and those issues include product ontology modeling, ontology construction and maintenance, and visualization. Our work presented herein may serve as a reference model for similar projects in the future.

Dynamic caching of query results for decision support systems

The response time of DSS (decision support system) queries is typically several orders of magnitude higher than the response time of OLTP (online transaction processing) queries. Since DSS queries are often submitted interactively, techniques for reducing their response time are becoming increasingly important. We argue that caching of query results is one such technique particularly well suited to the DSS environment. We have designed a query cache manager for such an environment. The cache manager can lookup query results from the cache either based on an exact query match or using a query split algorithm to efficiently find query results which subsume the submitted query. The cache manager dynamically maintains the cache content by deciding whether a newly generated query result should be admitted to the cache and if so, which query results should be evicted from the cache to free space for the new query result. The decisions are aimed at minimizing the query response time. The decisions are explicitly based on a cost function that considers the execution cost of each query, the size of each query result, the reference frequency to each result, the cost of maintenance of each result due to updates of the base tables, and the frequency of such updates. Experimental evaluation shows that our cache manager can improve performance on TPC-D like workloads.

Data Engineering Issues in E-Commerce and Services

E-Commerce Services.- An Approach to Detecting Shill-Biddable Allocations in Combinatorial Auctions.- Explanation Services and Request Refinement in User Friendly Semantic-Enabled B2C E-Marketplaces.- Customer Future Profitability Assessment: A Data-Driven Segmentation Function Approach.- Optimization of Automatic Navigation to Hidden Web Pages by Ranking-Based Browser Preloading.- Business Processes and Services.- Transforming Collaborative Business Process Models into Web Services Choreography Specifications.- Evaluation of IT Portfolio Options by Linking to Business Services.- Process Driven Data Access Component Generation.- Using Naming Tendencies to Syntactically Link Web Service Messages.- Data and Knowledge Engineering.- Maintaining Web Navigation Flows for Wrappers.- Mobile P2P Automatic Content Sharing by Ontology-Based and Contextualized Integrative Negotiation.- Integrating XML Sources into a Data Warehouse.- Remote-Specific XML Query Mobile Agents.- Business Models and Analysis.- A Process History Capture System for Analysis of Data Dependencies in Concurrent Process Execution.- Business Impact Analysis Using Time Correlations.- A Bottom-Up Workflow Mining Approach for Workflow Applications Analysis.- BestChoice: A Decision Support System for Supplier Selection in e-Marketplaces.- Web Services.- Semantic Web Services Enabled B2B Integration.- A Novel Genetic Algorithm for QoS-Aware Web Services Selection.- Analysis of Web Services Composition and Substitution Via CCS.- E-Commerce Systems.- Modified Naive Bayes Classifier for E-Catalog Classification.- A Sentinel Based Exception Diagnosis in Market Based Multi-Agent Systems.- Dynamical E-Commerce System for Shopping Mall Site Through Mobile Devices.- PROMOD: A Modeling Tool for Product Ontology.

Ontological modeling of e-catalogs using EER and description logics

Electronic catalog contains rich semantics associated with products, and serves as a challenging domain for ontology application. Ontology is concerned with the nature and relations of being. It can play a crucial role in e-commerce as a formalization of e-Catalogs. Description logics provide a theoretical core for most of the current ontology languages. In this paper, we present an ontological model of e-Catalogs. Our goal is to represent the semantic information of e-Catalog in a conceptual model, and then to construct a formally sound ontology. We take an extended entity relationship approach to denote the fundamental set of modeling constructs, and present corresponding description logic representation for each construct. Additional semantic knowledge can be represented directly in description logic.

Practical issues for building a product ontology system

A base of clearly defined product information is a key foundation for an e-commerce system. The manipulation and exchange of semantically enriched and precise product information can enhance the quality of an e-commerce system and offer a high level of interoperability with other systems. Product information consists of product attributes and the relationships between products. Product categorization (or classification) is one type of such relationships. Ontology can play an important role in the formalization of product information. Although the idea of utilizing ontology for e-catalogs has been raised before, we are yet to find an operational implementation of applying ontology in the domain. In this paper, we report on our recent effort to build an operational product ontology system for the government procurement service. The system is designed to serve as a product ontology knowledge base; not only for the design and construction of product databases but also for search and discovery of products. We introduce some of the issues that we have experienced in the project, so that our work may serve as a reference model for similar projects in the future.

CST-trees: cache sensitive t-trees

Researchers have modified existing index structures into ones optimized for CPU cache performance in main memory database environments. A Cache Sensitive B+-Tree is one of them. It is designed to minimize the impact of cache misses for B+-Trees and it has been known to be more effective than other types of main memory index structure including T-Trees. In this paper, we introduce a Cache Sensitive T-Tree (CST-Tree) and show how T-Trees can also be redesigned to be cache sensitive. We present an experimental performance study which shows that our Cache Sensitive T-Trees can outperform the original T-Trees and Cache Sensitive B+-Trees on average 65 percent and 17 percent, respectively.

Roadmap for E-Commerce Standardization in Korea

ECIF (Integrated Forum on Electronic Commerce) is a Korean organization streamlining domestic private sector e-commerce standardization facilitation and promoting domestic/international discourse for the enhancement of Korea’s e-commerce competitiveness. Herein is presented a summary of the Roadmap for E-Commerce Standardization, a major Forum project since early 2000. First, we overview the background and the motivation of the roadmap project. The roadmap contains an e-commerce and e-commerce standardization overview, e-commerce technology classifications, an e-commerce core technology standardization status analysis, and a core technology classification standardization timetable. The roadmap project implementation scheme is introduced. Most of the material within the paper is based on the Roadmap version 2.0 and version 3.0, the second- and third-year artifacts. Also incorporated are some features of the ongoing fourth-year development.

A Unified Approach for Software Policy Modeling: Incorporating Implementation into a Modeling Methodology

Works in some software project domains consist of many small projects of which development cycles are relatively quite short and numerous. In such domains, the software development policy such as the work assignment policy needs not only its modeling but also needs the prompt implementation of the model. However, incorporating the implementation into the modeling methodology has not been paid great attention to in the areas of software process. Each organization may have different situations in human resources and tasks as well as practical constraints, and it may not be feasible to devise a single model to cover all policies. In this paper, we do not focus on presenting a universal model for the work assignment policy. Instead, we provide a meta-model based methodology which enables us to develop an extensible model for an organization. In our modeling methodology, the model for the work assignment policy and its implementation are incorporated. We employ UML and ConceptBase. We highlight how a model illustrated in UML is generated in ConceptBase codes. And finally, we introduce our experience from the use of a prototype system in actual software project field.