Indexing file contents is a powerful means of helping users locate documents, software, and other types of data among large repositories. In environments that contain many different types of data, content indexing requires type-specific processing to extract information effectively. We present a model for type-specific, user-customizable information extraction, and a system implementation calledEssence. This software structure allows users to associate specialized extraction methods with ordinary files, providing the illusion of an object-oriented file system that encapsulates indexing methods within files. By exploiting the semantics of common file types, Essence generates compact yet representative file summaries that can be used to improve both browsing and indexing in resource discovery systems. Essence can extract information from most of the types of files found in common file systems, including files with nested structure (such as compressed “tar” files). Essence interoperates with a number of different search/index systems (such as WAIS and Glimpse), as part of the Harvest system.

In this paper we consider the problem of choosing among a collection of replicated servers, focusing on the question of how to make choices that segregate client/server traffic according to network topology.We explore the cost and effectiveness of a variety of approaches, ranging from those requiring routing layer support (e.g., anycast) to those that build location databases using application-level probe tools like traceroute. Weuncover a number of tradeoffs between effectiveness, network cost, ease of deployment, and portability across differenttypes of networks. We performed our experiments using a simulation parameterized by a topology collected from 7 survey sites across the United States, exploring a global collection of Network Time Protocol servers.

The Internet is quickly becoming an indispensable means of communication and collaboration, based on applications such as electronic mail, remote information retrieval, and multimedia conferencing. A fundamental problem for such applications is supporting resource discovery in a fashion that keeps pace with the Internet's exponential growth in size and diversity. Netfind is a scalable tool that locates current electronic mail addresses and other information about Internet users. Since the time we first deployed Netfind in 1990, it has evolved considerably, making use of more types of information sources. As well as more sophisticated mechanisms to gather and cross-correlate information. In this paper, we describe these techniques, and present a general framework for gathering and harnessing widely distributed information in a diverse and growing Internet environment. At present, Netfind gathers information from 17 different types of sources, providing a particularly thorough demonstration of an information gathering architecture.>

This paper presents evidence that several, judiciously placed file caches could reduce the volume of FTP traffic by 42%, and hence the volume of all NSFNET backbone traffic by 21%. In addition, if FTP client and server software automatically compressed data, this savings could increase to 27%. We believe that a hierarchical architecture of whole file caches, modeled after the existing name server's caching architecture, could become a valuable part of any internet.We derived these conclusions by performing trace driven simulations of various file caching architectures, cache sizes, and replacement policies. We collected the traces of file transfer traffic employed in our simulations on a network that connects the NSFNET backbone to a large, regional network. This particular regional network is responsible for about 5 to 7% of NSFNET traffic.While this paper's analysis and discussion focus on caching for FTP file transfer, the proposed caching architecture applies to caching objects from other internetwork services.

Wide area networks offer access to an increasing number and variety of resources. Yet, it is difficult to locate resources of interest, because of the scale and decentralized nature of the environment. The authors are interested in supporting a global confederation of loosely cooperating systems and users that share far more resources than can be completely organized. Therefore, mechanisms are needed to support incremental organization of the resources, based on the efforts of many geographically decentralized individuals, and a range of different information sources of varying degrees of quality. The authors describe a prototype implementation of a set of mechanisms intended to explore this problem in the specific domain of public Internet archives, accessible via the anonymous file transfer protocol. This is an interesting test case, because it encompasses a very large scale, administratively decentralized collection of resources, with considerably practical value.>

A prototype implementation has been built as part of the Heterogeneous Computer Systems project at the University of Washington. This service supports RPC binding and other applications in our heterogeneous environment. Measurements of the performance of this prototype show that it is close to that of the underlying name services, due largely to the use of specialized caching techniques.

Heterogeneity in hardware and software is an inevitable consequence of experimental computer research. At the University of Washington, the Heterogeneous Computer Systems (HCS) project is a major research and development effort whose goal is to simplify the interconnection of heterogeneous computer systems.