Su Myeon Kim

A survey of public Web Services

Enterprise IT infrastructures and their interfaces are migrating toward a service-oriented architecture, using Web Services (WS) as a de-facto implementation protocol. As a result, WS-generated traffic is expected to have a considerable impact on the Internet. Despite the high amount of interest in WS, there have been few studies regarding their characteristics. In this survey, we analyze publicly-accessible WS over a 9 month period. We study the evolution and distributions of the WS population, and message characteristics and response times of each WS. We also closely analyze two popular WS sites: Amazon and Google. Some of our initial results contradict common intuition. The number of public WS has not increased dramatically, although there are signs which indicate intensive ongoing activities in the WS domain. The geographic distribution of public WS is largely skewed. Most importantly, the sizes of WS responses and their variation are smaller than those of the existing Web objects.

A survey of public web services

This paper introduces a methodology to provide the first characterization of public Web Services in terms of their evolution, location, complexity, message size, and response time.

Maintaining consistency under isolation relaxation of web services transactions

For efficiently managing Web Services (WS) transactions which are executed across multiple loosely-coupled autonomous organizations, isolation is commonly relaxed. A Web services operation of a transaction releases locks on its resources once its jobs are completed without waiting for the completions of other operations. However, those early unlocked resources can be seen by other transactions, which can spoil data integrity and causes incorrect outcomes. Existing WS transaction standards do not consider this problem. In this paper, we propose a mechanism to ensure the consistent executions of isolation-relaxing WS transactions. The mechanism effectively detects inconsistent states of transactions with a notion of a completion dependency and recovers them to consistent states. We also propose a new Web services Transaction Dependency management Protocol (WTDP). WTDP helps organizations manage the WS transactions easily without data inconsistency. WTDP is designed to be compliant with a representative WS transaction standard, the Web Services Transactions specifications, for easy integration into existing WS transaction systems. We prototyped a WTDP-based WS transaction management system to validate our protocol.

CISS: An efficient object clustering framework for DHT-based peer-to-peer applications

In most DHT-based peer-to-peer systems, objects are totally declustered since such systems use a hash function to distribute objects evenly. However, such an object de-clustering can result in significant inefficiencies in advanced access operations such as multi-dimensional range queries, continuous updates, etc, which are common in many emerging peer-to-peer applications. In this paper, we propose CISS (Cooperative Information Sharing System), a framework that supports efficient object clustering for DHT-based peer-to-peer applications. CISS uses a Locality Preserving Function (LPF) instead of a hash function, thereby achieving a high level of clustering without requiring any changes to existing DHT implementations. To maximize the benefit of object clustering, CISS provides efficient routing protocols for multi-dimensional range queries and continuous updates. Furthermore, our cluster-preserving load balancing schemes distribute loads without hotspots while preserving the object clustering property. We demonstrate the performance benefits of CISS through extensive simulation.

DCF: an efficient data stream clustering framework for streaming applications

Streaming applications, such as environment monitoring and vehicle location tracking require handling high volumes of continuously arriving data and sudden fluctuations in these volumes while efficiently supporting multi-dimensional historical queries. The use of the traditional database management systems is inappropriate because they require excessive number of disk I/O in continuously updating massive data streams. In this paper, we propose DCF (Data Stream Clustering Framework), a novel framework that supports efficient data stream archiving for streaming applications. DCF can reduce a great amount of disk I/O in the storage system by grouping incoming data into clusters and storing them instead of raw data elements. In addition, even when there is a temporary fluctuation in the amount of incoming data, it can stably support storing all incoming raw data by controlling the cluster size. Our experimental results show that our approach significantly reduces the number of disk accesses in terms of both inserting and retrieving data.

Accelerating Database Processing at e-Commerce Sites

Most e-commerce Web sites dynamically generate their contents through a three-tier server architecture composed of a Web server, an application server, and a database server. In such an architecture, the database server easily becomes a bottleneck to the overall performance. In this paper, we propose WDBAccel, a high-performance database server accelerator that significantly improves the throughput of the database processing, and thus that of the overall Web site. WDBAccel eliminates costly, complex query processing needed to obtain query results by reusing previous query results for subsequent queries. This differentiates WDBAccel from other database cache systems, which replicate a database into multiple conventional DBMS’s and distribute queries among them. We evaluate the performance of WDBAccel by using the queries of the TPC-W benchmark. The measurement results show that WDBAccel outperforms DBMS-based cache systems by up to an order of magnitude.

A scalable update management mechanism for query result caching systems at database-driven web sites

A key problem in using caching technology for dynamic contents lies in update management. An update management scheme should be very efficient without imposing much extra burden to the system, especially to the original database server. We propose an scalable update management mechanism for query result caching in database-backed Web sites. Our mechanism employs a two-phase consistency checking method, which prunes out unaffected queries at the earliest possible moment. The method scales well with a high number of cached instances.

A framework for handling dependencies among web services transactions

This paper proposes an effective Web services (WS) transaction management framework to automatically manage inconsistencies occurred by relaxing isolation of WS transactions.

Content Aggregation Middleware (CAM) for fast development of high performance web Syndication services

The rapid expansion of the Internet accompanies a serious side effect. Since there are too many information providers, it is very difficult to obtain the contents best fitting to customers’ needs. Web Syndication Services (WSS) are emerging as solutions to the information flooding problem. How-ever, even with its practical importance, WSS has not been much studied yet. In this paper, we propose the Content Aggregation Middleware (CAM). It provides a WSS with a content gathering substratum effective in gathering and processing data from many different source sites. Using the CAM, WSS provider can build up a new service without involving the details of complicated content aggregation procedures, and thus concentrate on developing the service logic. We describe the design, implementation, and performance of the CAM.

Accelerating Database Processing at Database-Driven Web Sites

Most commercial Web sites dynamically generate their contents through a three-tier server architecture composed of a Web server, an application server, and a database server. In such an architecture, the database server easily becomes a bottleneck to the overall performance. In this paper, we propose WDBAccel, a high-performance database server accelerator that significantly improves the throughput of database processing. WDBAccel eliminates costly, complex query processing needed to obtain query results by reusing the results from previous queries for subsequent queries. This differentiates WDBAccel from other database cache systems, which employ traditional query processing. WDBAccel further improves its performance by fully utilizing main memory as the primary storage. This paper presents the design and implementation of the WDBAccel as well as the results of performance evaluation with a prototype.