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With the proliferation of the world's "information highways" a renewed interest in efficient document indexing techniques has come about. In this paper, the problem of incremental updates of inverted lists is addressed using a new dual-structure index data structure. The index dynamically separates long and short inverted lists and optimizes the retrieval, update, and storage of each type of list. To study the behavior of the index, a space of engineering tradeoffs which range from optimizing update time to optimizing query performance is described. We quantitatively explore this space by using actual data and hardware in combination with a simulation of an information retrieval system. We then describe the best algorithm for a variety of criteria. 1 Introduction As the world's "information highways" proliferate and grow in capacity, they are providing access to an ever growing number of electronic document repositories. At each repository, the number of documents available on-line is...

: : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : xii 1 Introduction : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1 1. The problem : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1 2. Overview of thesis : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2 3. Contribution of our work : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 3 2 Taxonomy of traffic characteristics : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 5 1. Aggregation granularity : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 5 2. Host versus network centric perspective : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 7 3. Host centric perspective : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 7 1. Delay and jitter : : : : : ...

The huge amount of information available in the currently evolving world wide information infrastructure at any one time can easily overwhelm end-users. One way to address the information explosion is to use an “information filtering agent ” which can select information according to the interest and/or need of an end-user. However, at present few such information filtering agents exist. In this study, we evaluate the use of feature-based approaches to user modcling with the purpose of creating a filtering agent for the video-on-demand application. We evaluate several feature and clique-based models for 10 voluntary subjects who provided ratings for the movies. Our preliminary results suggest that feature-based selection can be a useful tool to recommend movies according to the taste of the user and can be as effective as a movie rating expert. We compare our feature-based approach with a clique-based approach, which has advantages whcrc information from other users is available.

We describe a service for locating distributed objects identified by location-independent object identifiers. An object in our model is physically distributed, with multiple active copies on different machines. Processes must bind to an object in order to invoke its methods. Part of the binding protocol is concerned with contacting the object, which offers one or more contact points. A contact point is associated with an active part of the distributed object, and describes exactly how and where initial communication should take place. An object can change its contact points in the course of time, thus exhibiting migration behavior. Finding an object’s contact points is the essence of our location service. Our model is based on a worldwide distributed search tree, capable of handling trillions of distributed objects. The tree adapts dynamically to individual migration patterns. By exploiting an object’s relative stability with respect to a region, combined with the use of pointer caches, an object can be contacted through a search path of only length two. We present the architecture of our location service, including its update and lookup mechanism, and discuss its scalability. 1

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this paper, we use the term mobile object to collectively refer to any component - implemented in hardware, software, or a combination thereof- that is capable of changing locations. We assume that a mobile object can be distributed or replicated across multiple locations, meaning that there may be several locations where the object resides at the same time. This can be the case, for example, with a whiteboard application shared between a number of mobile users. The existence of (worldwide) mobile objects introduces a location problem: The need for a scalable facility that maintains a binding (i.e., a mapping) between an object's permanent name and its current address(es). Such facilities are normally offered by wide-area naming systems such as the Internet's Domain Name System (DNS) [9], DEC's Global Name Service (GNS) [10], and the X.500 Directory Ser- vice [11]

Mosaic traffic (i.e., World-Wide Web) is the fastest growing component of the aggregate packet and byte traffic on the NSFNET backbone. Modeling the workload characteristics of these mosaic sessions is therefore deemed important in any simulation study of the Internet or future high speed networks. The ATM-TN TeleSim project has designed and implemented a synthetic workload model for Internet mosaic traffic, to be used as input to a parallel simulator for high speed ATM networks. This paper describes the workload characterization and modeling process for this synthetic workload model, as well as the design, implementation, and validation of this traffic model. 1 INTRODUCTION To many people, "the Internet" is synonymous with "the Information Superhighway". The Internet provides access to a vast array of information services and information resources. Information services include traditional services such as electronic mail, file transfer, and remote login, as well as new services such...

We present the architecture for data collection for the NSFNET backbone and difficulties with using the collected statistics for long-term network forecasting of certain traffic aspects. We describe relevant aspects of the NSFNET backbone architecture and the instrumentation for statistics collection. We then present long-term NSFNET data to elucidate long-term trends in both the reachability of Internet components via the NSFNET as well as the growing cross-section of traffic. We focus on the difficulties of forecasting and planning in an infrastructure whose protocol architecture and instrumentation for data collection was not designed to support such objectives. I. Introduction While initially conceived as a demonstration project of a then new networking technology for the United States federal government, today's Internet aggregates traffic from a far wider set of constituencies. As the number of client networks of the Internet heads into the tens of thousands, the image of a ubiq...

Access to on-line information via the Web is exploding. Index and retrieval engines already start to integrate a huge variety of heterogeneous repositories. However, the heterogeneity issue remains, both in terms of the search formats and the formats of the result pages. In this paper,