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Articles 961 - 990 of 1060

Full-Text Articles in Numerical Analysis and Scientific Computing

Tournament Versus Fitness Uniform Selection, Shane Legg, Marcus Hutter, Akshat Kumar Jun 2004

Tournament Versus Fitness Uniform Selection, Shane Legg, Marcus Hutter, Akshat Kumar

Research Collection School Of Computing and Information Systems

In evolutionary algorithms a critical parameter that must be tuned is that of selection pressure. If it is set too low then the rate of convergence towards the optimum is likely to be slow. Alternatively if the selection pressure is set too high the system is likely to become stuck in a local optimum due to a loss of diversity in the population. The recent Fitness Uniform Selection Scheme (FUSS) is a conceptually simple but somewhat radical approach to addressing this problem - rather than biasing the selection towards higher fitness, FUSS biases selection towards sparsely populated fitness levels. In …

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Steganographic Schemes For File System And B-Tree, Hwee Hwa Pang, Kian-Lee Tan, Xuan Zhou Jun 2004

Steganographic Schemes For File System And B-Tree, Hwee Hwa Pang, Kian-Lee Tan, Xuan Zhou

Research Collection School Of Computing and Information Systems

While user access control and encryption can protect valuable data from passive observers, these techniques leave visible ciphertexts that are likely to alert an active adversary to the existence of the data. We introduce StegFD, a steganographic file driver that securely hides user-selected files in a file system so that, without the corresponding access keys, an attacker would not be able to deduce their existence. Unlike other steganographic schemes proposed previously, our construction satisfies the prerequisites of a practical file system in ensuring the integrity of the files and maintaining efficient space utilization. We also propose two schemes for implementing …

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Parameter Inference Of Queueing Models For It Systems Using End-To-End Measurements, Laura Wynter, Cathy H. Xia, Fan Zhang Jun 2004

Parameter Inference Of Queueing Models For It Systems Using End-To-End Measurements, Laura Wynter, Cathy H. Xia, Fan Zhang

Research Collection School Of Computing and Information Systems

he scope of available applications, IT systems increase at a fascinating rate in both size and complexity. For example, today, a typical Web service hosting center may have hundreds of nodes and dozens of different applications simultaneously running on it. Each of the nodes in turn has often multiple processors and layered caches. These nodes make use of both local and shared storage systems. The size and complexity of such systems make performance modeling much more difficult, if at all tractable. Detailed modeling, fine tuning and accurate analysis can be carried out only on very small IT systems or very …

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Performance Planning, Quality-Of-Service, And Pricing Under Competition, Corinne Touati, Parijat Dube, Laura Wynter May 2004

Performance Planning, Quality-Of-Service, And Pricing Under Competition, Corinne Touati, Parijat Dube, Laura Wynter

Research Collection School Of Computing and Information Systems

In this work we model the relationship between the capacity and the Quality of Service (QoS) offered by the firm in a competitive scenario of two firm’s working to maximize their profits. Using simple queueing theoretic models we study the sensitivity of a firm’s market share to price, capacity and market size. Our preliminary studies yield important properties of the equilibrium solution which may further provide important “engineering” guidelines for performance planning and pricing strategies.

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Dynamic Offloading In A Multi-Provider Environment: A Behavioral Framework For Use In Influencing Peering, Zhen Liu, Vishal Misra, Laura Wynter Apr 2004

Dynamic Offloading In A Multi-Provider Environment: A Behavioral Framework For Use In Influencing Peering, Zhen Liu, Vishal Misra, Laura Wynter

Research Collection School Of Computing and Information Systems

We pose the question of how to encourage the resource sharing in a distributed, multi-provider environment, where each node, or provider, has local work but is able to accept additional work from other nodes/providers if there is available capacity. An instance of such an environment is found in content delivery, where. numerous, competing providers can work together if enough benefit is to be gained from doing so. We model individual provider behavior as essentially selfish, and then propose pricing schemes to exploit the selfishness to achieve system wide performance gains. We employ a game theoretic framework to analyze the problem, …

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Efficient Group Pattern Mining Using Data Summarization, Yida Wang, Ee Peng Lim, San-Yih Hwang Mar 2004

Efficient Group Pattern Mining Using Data Summarization, Yida Wang, Ee Peng Lim, San-Yih Hwang

Research Collection School Of Computing and Information Systems

In group pattern mining, we discover group patterns from a given user movement database based on their spatio-temporal distances. When both the number of users and the logging duration are large, group pattern mining algorithms become very inefficient. In this paper, we therefore propose a spherical location summarization method to reduce the overhead of mining valid 2-groups. In our experiments, we show that our group mining algorithm using summarized data may require much less execution time than that using non-summarized data.

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Group Nearest Neighbor Queries, Dimitris Papadias, Qiongmao Shen, Yufei Tao, Kyriakos Mouratidis Mar 2004

Group Nearest Neighbor Queries, Dimitris Papadias, Qiongmao Shen, Yufei Tao, Kyriakos Mouratidis

Research Collection School Of Computing and Information Systems

Given two sets of points P and Q, a group nearest neighbor (GNN) query retrieves the point(s) of P with the smallest sum of distances to all points in Q. Consider, for instance, three users at locations q1 , q2 and q3 that want to find a meeting point (e.g., a restaurant); the corresponding query returns the data point p that minimizes the sum of Euclidean distances |pqi| for 1 ≤i ≤3. Assuming that Q fits in memory and P is indexed by an R-tree, we propose several algorithms for finding the group nearest neighbors efficiently. As a second step, …

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Spatial Queries In The Presence Of Obstacles, Jun Zhang, Dimitris Papadias, Kyriakos Mouratidis, Manli Zhu Mar 2004

Spatial Queries In The Presence Of Obstacles, Jun Zhang, Dimitris Papadias, Kyriakos Mouratidis, Manli Zhu

Research Collection School Of Computing and Information Systems

Despite the existence of obstacles in many database applications, traditional spatial query processing utilizes the Euclidean distance metric assuming that points in space are directly reachable. In this paper, we study spatial queries in the presence of obstacles, where the obstructed distance between two points is defined as the length of the shortest path that connects them without crossing any obstacles. We propose efficient algorithms for the most important query types, namely, range search, nearest neighbors, e-distance joins and closest pairs, considering that both data objects and obstacles are indexed by R-trees. The effectiveness of the proposed solutions is verified …

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An Automated Algorithm For Extracting Website Skeleton, Zehua Liu, Wee-Keong Ng, Ee Peng Lim Mar 2004

An Automated Algorithm For Extracting Website Skeleton, Zehua Liu, Wee-Keong Ng, Ee Peng Lim

Research Collection School Of Computing and Information Systems

The huge amount of information available on the Web has attracted many research efforts into developing wrappers that extract data from webpages. However, as most of the systems for generating wrappers focus on extracting data at page-level, data extraction at site-level remains a manual or semi-automatic process. In this paper, we study the problem of extracting website skeleton, i.e. extracting the underlying hyperlink structure that is used to organize the content pages in a given website. We propose an automated algorithm, called the Sew algorithm, to discover the skeleton of a website. Given a page, the algorithm examines hyperlinks in …

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Authenticating Query Results In Edge Computing, Hwee Hwa Pang, Kian-Lee Tan Mar 2004

Authenticating Query Results In Edge Computing, Hwee Hwa Pang, Kian-Lee Tan

Research Collection School Of Computing and Information Systems

Edge computing pushes application logic and the underlying data to the edge of the network, with the aim of improving availability and scalability. As the edge servers are not necessarily secure, there must be provisions for validating their outputs. This paper proposes a mechanism that creates a verification object (VO) for checking the integrity of each query result produced by an edge server - that values in the result tuples are not tampered with, and that no spurious tuples are introduced. The primary advantages of our proposed mechanism are that the VO is independent of the database size, and that …

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Hiding Data Accesses In Steganographic File System, Xuan Zhou, Hwee Hwa Pang, Kian-Lee Tan Mar 2004

Hiding Data Accesses In Steganographic File System, Xuan Zhou, Hwee Hwa Pang, Kian-Lee Tan

Research Collection School Of Computing and Information Systems

To support ubiquitous computing, the underlying data have to be persistent and available anywhere-anytime. The data thus have to migrate from devices local to individual computers, to shared storage volumes that are accessible over open network. This potentially exposes the data to heightened security risks. We propose two mechanisms, in the context of a steganographic file system, to mitigate the risk of attacks initiated through analyzing data accesses from user applications. The first mechanism is intended to counter attempts to locate data through updates in between snapshots - in short, update analysis. The second mechanism prevents traffic analysis - identifying …

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Web Usage Mining: Algorithms And Results, Ee Peng Lim, Yew-Kwong Woon, Wee-Keong Ng Jan 2004

Web Usage Mining: Algorithms And Results, Ee Peng Lim, Yew-Kwong Woon, Wee-Keong Ng

Research Collection School Of Computing and Information Systems

No abstract provided.

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Analysis Of A Yield Management Model For On Demand Computing Centers, Yezekael Hayel, Laura Wynter, Parijat Dube Jan 2004

Analysis Of A Yield Management Model For On Demand Computing Centers, Yezekael Hayel, Laura Wynter, Parijat Dube

Research Collection School Of Computing and Information Systems

The concept of yield management for IT infrastructures, and in particular for on demand IT utilities was recently introduced in [17]. The present paper provides a detailed analysis of that model, both in simplified cases where an analytical analysis is possible, and numerically on larger problem instances, and confirms the significant revenue benefit that can accrue through use of yield management in an IT on demand operating environment.

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Predicting Nonlinear Network Traffic Using Fuzzy Neural Network, Zhaoxia Wang, Tingzhu Hao, Zengqiang Chen, Zhuzhi Yuan Dec 2003

Predicting Nonlinear Network Traffic Using Fuzzy Neural Network, Zhaoxia Wang, Tingzhu Hao, Zengqiang Chen, Zhuzhi Yuan

Research Collection School Of Computing and Information Systems

Network traffic is a complex and nonlinear process, which is significantly affected by immeasurable parameters and variables. This paper addresses the use of the five-layer fuzzy neural network (FNN) for predicting the nonlinear network traffic. The structure of this system is introduced in detail. Through training the FNN using back-propagation algorithm with inertia] terms the traffic series can be well predicted by this FNN system. We analyze the performance of the FNN in terms of prediction ability as compared with solely neural network. The simulation demonstrates that the proposed FNN is superior to the solely neural network systems. In addition, …

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Xstamps: A Multiversion Timestamps Concurrency Control Protocol For Xml Data, Khin-Myo Win, Wee-Keong Ng, Ee Peng Lim Dec 2003

Xstamps: A Multiversion Timestamps Concurrency Control Protocol For Xml Data, Khin-Myo Win, Wee-Keong Ng, Ee Peng Lim

Research Collection School Of Computing and Information Systems

With the tremendous growth of XML data over the Web, efficient management of such data becomes a new challenge for database community. Several data management solutions, proposed in recent years, extend the capability of traditional database systems to meet the needs of XML data while alternative approaches introduce new generation databases, named as native XML database management systems. Although traditional databases have mature transaction management and concurrency control techniques, there is still a need to tailor techniques for native XML databases in order to deal with distinct characteristics of XML. In this paper, we propose XStamps, a multiversion timestamps concurrency …

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Paper For An Educational Digital Library, Dion Hoe-Lian Goh, Yin-Leng Theng, Ming Yin, Ee Peng Lim Dec 2003

Paper For An Educational Digital Library, Dion Hoe-Lian Goh, Yin-Leng Theng, Ming Yin, Ee Peng Lim

Research Collection School Of Computing and Information Systems

GeogDL is a digital library of geography examination resources designed to assist students in revising for a national geography examination in Singapore. As part of an iterative design process, we carried out participatory design and brainstorming with student and teacher design partners. The first study involved prospective student design partners. In response to the first study, we describe in this paper an implementation of PAPER – Personalised Adaptive Pathways for Exam Resources – a new bundle of personalized, interactive services containing a mock exam and a personal coach. The mock exam provides a simulation of the actual geography examination while …

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Pricing And Qos Of Information Services In A Competitive Market, Zhen Liu, Laura Wynter, Cathy Xia Nov 2003

Pricing And Qos Of Information Services In A Competitive Market, Zhen Liu, Laura Wynter, Cathy Xia

Research Collection School Of Computing and Information Systems

Design of e-commerce services that are competitive in a quickly responding market requires the analyses of prices and price structures. We develop a general model of an e-commerce market that allows us to analyze optimal price structures, both flat and usage-based. Based on the price structure of a major web hosting provider, we consider single-tier and two-tier (burst-rate) pricing, and our result suggests that the more complex two-tier structure may not be worth the marketing effort, as the firm's equilibrium profits will not increase through the use of this structure. An essential feature of our approach is that we model …

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Web Unit Mining: Finding And Classifying Subgraphs Of Web Pages, Aixin Sun, Ee Peng Lim Nov 2003

Web Unit Mining: Finding And Classifying Subgraphs Of Web Pages, Aixin Sun, Ee Peng Lim

Research Collection School Of Computing and Information Systems

In web classification, most researchers assume that the objects to classify are individual web pages from one or more web sites. In practice, the assumption is too restrictive since a web page itself may not always correspond to a concept instance of some semantic concept (or category) given to the classification task. In this paper, we want to relax this assumption and allow a concept instance to be represented by a subgraph of web pages or a set of web pages. We identify several new issues to be addressed when the assumption is removed, and formulate the web unit mining …

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Ssm: Fast Construction Of The Optimized Segment Support Map, Kok-Leong Ong, Wee-Keong Ng, Ee Peng Lim Sep 2003

Ssm: Fast Construction Of The Optimized Segment Support Map, Kok-Leong Ong, Wee-Keong Ng, Ee Peng Lim

Research Collection School Of Computing and Information Systems

Computing the frequency of a pattern is one of the key operations in data mining algorithms. Recently, the Optimized Segment Support Map (OSSM) was introduced as a simple but powerful way of speeding up any form of frequency counting satisfying the monotonicity condition. However, the construction cost to obtain the ideal OSSM is high, and makes it less attractive in practice. In this paper, we propose the FSSM, a novel algorithm that constructs the OSSM quickly using a FP-Tree. Given a user-defined segment size, the FSSM is able to construct the OSSM at a fraction of the time required by …

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On Mining Group Patterns Of Mobile Users, Yida Wang, Ee Peng Lim, San-Yih Hwang Sep 2003

On Mining Group Patterns Of Mobile Users, Yida Wang, Ee Peng Lim, San-Yih Hwang

Research Collection School Of Computing and Information Systems

In this paper, we present a group pattern mining approach to derive the grouping information of mobile device users based on the spatio-temporal distances among them. Group patterns of users are determined by a distance threshold and a minimum duration. To discover group patterns, we propose the AGP and VG-growth algorithms that are derived from the Apriori and FP-growth algorithms respectively. We further evaluate the efficiencies of these two algorithms using synthetically generated user movement data.

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A Study On Tolerable Waiting Time: How Long Are Web Users Willing To Wait?, Fiona Fui-Hoon Nah Aug 2003

A Study On Tolerable Waiting Time: How Long Are Web Users Willing To Wait?, Fiona Fui-Hoon Nah

Research Collection School Of Computing and Information Systems

The WWW has become an important channel for information access, electronic commerce, and publication. With an exponential increase in the number of Web users and the popularity of multimedia technology, users often face a long waiting time for downloading Web pages. Although various technologies and techniques have been implemented to alleviate the situation and to comfort the impatient users, little research has been done to assess what constitutes an acceptable and tolerable waiting time for Web users. This research reviews the literature on computer response time and users’ waiting time, and assesses Web users’ tolerable waiting time in information retrieval. …

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Adaptive Filters For Continuous Queries Over Distributed Data Stream, Chris Olston, Jing Jiang, Jennifer Widom Jun 2003

Adaptive Filters For Continuous Queries Over Distributed Data Stream, Chris Olston, Jing Jiang, Jennifer Widom

Research Collection School Of Computing and Information Systems

We consider an environment where distributed data sources continuously stream updates to a centralized processor that monitors continuous queries over the distributed data. Significant communication overhead is incurred in the presence of rapid update streams, and we propose a new technique for reducing the overhead. Users register continuous queries with precision requirements at the central stream processor, which installs filters at remote data sources. The filters adapt to changing conditions to minimize stream rates while guaranteeing that all continuous queries still receive the updates necessary to provide answers of adequate precision at all times. Our approach enables applications to trade …

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Using Support Vector Machines For Terrorism Information Extraction, Aixin Sun, Myo-Myo Naing, Ee Peng Lim, Wai Lam Jun 2003

Using Support Vector Machines For Terrorism Information Extraction, Aixin Sun, Myo-Myo Naing, Ee Peng Lim, Wai Lam

Research Collection School Of Computing and Information Systems

Information extraction (IE) is of great importance in many applications including web intelligence, search engines, text understanding, etc. To extract information from text documents, most IE systems rely on a set of extraction patterns. Each extraction pattern is defined based on the syntactic and/or semantic constraints on the positions of desired entities within natural language sentences. The IE systems also provide a set of pattern templates that determines the kind of syntactic and semantic constraints to be considered. In this paper, we argue that such pattern templates restricts the kind of extraction patterns that can be learned by IE systems. …

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On Querying Geospatial And Georeferenced Metadata Resources In Gportal, Zehua Liu, Ee Peng Lim, Wee-Keong Ng, Dion Hoe-Lian Goh May 2003

On Querying Geospatial And Georeferenced Metadata Resources In Gportal, Zehua Liu, Ee Peng Lim, Wee-Keong Ng, Dion Hoe-Lian Goh

Research Collection School Of Computing and Information Systems

G-Portal is a web portal system providing a range of digital library services to access geospatial and georeferenced resources on the Web. Among them are the storage and query subsystems that provide a central repository of metadata resources organized under different projects. In GPortal, all metadata resources are represented in XML (Extensible Markup Language) and they are compliant to some resource schemas de.ned by their creators. The resource schemas are extended versions of a basic resource schema making it easy to accommodate all kinds of metadata resources while maintaining the portability of resource data. To support queries over the geospatial …

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Efficient Native Xml Storage System (Enaxs), Khin-Myo Win, Wee-Keong Ng, Ee Peng Lim Apr 2003

Efficient Native Xml Storage System (Enaxs), Khin-Myo Win, Wee-Keong Ng, Ee Peng Lim

Research Collection School Of Computing and Information Systems

XML is a self-describing meta-language and fast emerging as a dominant standard for Web data exchange among various applications. With the tremendous growth of XML documents, an efficient storage system is required to manage them. The conventional databases, which require all data to adhere to an explicitly specified rigid schema, are unable to provide an efficient storage for tree-structured XML documents. A new data model that is specifically designed for XML documents is required. In this paper, we propose a new storage system, named Efficient Native XML Storage System (ENAXS), for large and complex XML documents. ENAXS stores all XML …

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Hierarchical Text Classification Methods And Their Specification, Ee Peng Lim, Aixin Sun, Wee-Keong Ng Mar 2003

Hierarchical Text Classification Methods And Their Specification, Ee Peng Lim, Aixin Sun, Wee-Keong Ng

Research Collection School Of Computing and Information Systems

Hierarchical text classification refers to assigning text documents to the categories in a given category tree based on their content. With large number of categories organized as a tree, hierarchical text classification helps users to find information more quickly and accurately. Nevertheless, hierarchical text classification methods in the past have often been constructed in a proprietary manner. The construction steps often involve human efforts and are not completely automated. In this chapter, we therefore propose a specification language known as HCL (Hierarchical Classification Language). HCL is designed to describe a hierarchical classification method including the definition of a category tree …

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Stegfs: A Steganographic File System, Hwee Hwa Pang, Kian-Lee Tan, Xuan Zhou Mar 2003

Stegfs: A Steganographic File System, Hwee Hwa Pang, Kian-Lee Tan, Xuan Zhou

Research Collection School Of Computing and Information Systems

While user access control and encryption can protect valuable data from passive observers, those techniques leave visible ciphertexts that are likely to alert an active adversary to the existence of the data, who can then compel an authorized user to disclose it. This paper introduces StegFS, a steganographic file system that aims to overcome that weakness by offering plausible deniability to owners of protected files. StegFS securely hides user-selected files in a file system so that, without the corresponding access keys, an attacker would not be able to deduce their existence, even if the attacker is thoroughly familiar with the …

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Instance Based Attribute Identification In Database Integration, Ee Peng Lim, Cecil Chua, Roger Hsiang-Li Chiang Jan 2003

Instance Based Attribute Identification In Database Integration, Ee Peng Lim, Cecil Chua, Roger Hsiang-Li Chiang

Research Collection School Of Computing and Information Systems

Most research on attribute identification in database integration has focused on integrating attributes using schema and summary information derived from the attribute values. No research has attempted to fully explore the use of attribute values to perform attribute identification. We propose an attribute identification method that employs schema and summary instance information as well as properties of attributes derived from their instances. Unlike other attribute identification methods that match only single attributes, our method matches attribute groups for integration. Because our attribute identification method fully explores data instances, it can identify corresponding attributes to be integrated even when schema information …

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Performance Measurement Framework For Hierarchical Text Classification, Ee Peng Lim, Aixin Sun, Wee-Keong Ng Jan 2003

Performance Measurement Framework For Hierarchical Text Classification, Ee Peng Lim, Aixin Sun, Wee-Keong Ng

Research Collection School Of Computing and Information Systems

Hierarchical text classification or simply hierarchical classification refers to assigning a document to one or more suitable categories from a hierarchical category space. In our literature survey, we have found that the existing hierarchical classification experiments used a variety of measures to evaluate performance. These performance measures often assume independence between categories and do not consider documents misclassified into categories that are similar or not far from the correct categories in the category tree. In this paper, we therefore propose new performance measures for hierarchical classification. The proposed performance measures consist of category similarity measures and distance-based measures that consider …

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Advances In Mobile Commerce Technologies, Ee Peng Lim, Keng Siau Jan 2003

Advances In Mobile Commerce Technologies, Ee Peng Lim, Keng Siau

Research Collection School Of Computing and Information Systems

No abstract provided.

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