As larger and more heterogeneous text databases become available, information retrieval research will depend on the development of powerful, efficient and flexible retrieval engines. In this paper, we describe a retrieval system (INQUERY) that is based on a probabilistic retrieval model and provides support for sophisticated indexing and complex query formulation. INQUERY has been used successfully with databases containing nearly 400,000 documents. 1 Introduction The increasing interest in sophisticated information retrieval (IR) techniques has led to a number of large text databases becoming available for research. The size of these databases, both in terms of the number of documents in them, and the length of the documents that are typically full text, has presented significant challenges to IR researchers who are used to experimenting with two or three thousand document abstracts. In order to carry out research with different types of text representations, retrieval models, learni...

Software reuse is the process ofcreating software systems from existing software rather than building software systems from scratch. ‘l’his simple yet powerful vision was introduced in 1968. Software reuse has, however, failed to become a standard software engineering practice. In an attempt to understand why, researchers have renewed their interest in software reuse and in the obstacles to implementing it. This paper surveys the different approaches to software reuse found in the research literature. It uses a taxonomy to describe and compare the different approaches and make generalizations about the field of software reuse. The taxonomy characterizes each reuse approach interms of its reusable artifacts and the way these artifacts are abstracted, selected, speciahzed, and integrated. Abstraction plays a central role in software reuse. Concise and expressive abstractions are essential if software artifacts are to be effectively reused. The effectiveness of a reuse technique can be evaluatedin terms of cognztzue dwtance-an intuitive gauge of the intellectual effort required to use the technique. Cognitive distance isreduced in two ways: (l) Higher level abstractions ina reuse technique

Computer program input generally has some structure; in fact, every computer program

To simplify the task of obtaining information from the vast number of information sources that are available on the World Wide Web (WWW), we are building tools to build information mediators for extracting and integrating data from multiple Web sources. In a mediator based approach, wrappers are built around individual information sources, that provide translation between the mediator query language and the individual source. We present an approach for semi-automatically generating wrappers for structured internet sources. The key idea is to exploit formatting information in Web pages from the source to hypothesize the underlying structure of a page. From this structure the system generates a wrapper that facilitates querying of a source and possibly integrating it with other sources. We demonstrate the ease with which we are able to build wrappers for a number of Web sources using our implemented wrapper generation toolkit. 1. Introduction We are building information agents or media...

The Transmogrifier C hardware description language is almost identical to the C programming language, making it attractive to the large community of C-language programmers. This paper describes the semantics of the language and presents a Transmogrifier C compiler that targets the Xilinx 4000 FPGA. The compiler is operational and has produced several working circuits, including a graphics display driver.

research relevant to the design and application of high performance scientific computers. We test our ideas by designing, building, and using real systems. The systems we build are research prototypes; they are not intended to become products. There is a second research laboratory located in Palo Alto, the Systems Research Center (SRC). Other Digital research groups are located in Paris (PRL) and in Cambridge,

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Interposition agents are a well known device for attaching legacy applications to distributed system.s However, agents are difficult to build and are often large, monolithic pieces of software which are suited only to limited applications or systems. We solve this problem with Bypass, a language and a tool for quickly building multiple small agents that can be combined together to create powerful yet manageable software.

Lint is a command which examines C source programs, detecting a number of bugs and obscurities. It enforces the type rules of C more strictly than the C compilers. It may also be used to enforce a number of portability restrictions involved in moving programs between different machines and/or operating systems. Another option detects a number of wasteful, or error prone, constructions which nevertheless are, strictly speaking, legal. Lint accepts multiple input files and library specifications, and checks them for consistency. The separation of function between lint and the C compilers has both historical and practical rationale. The compilers turn C programs into executable files rapidly and efficiently. This is possible in part because the compilers do not do sophisticated type checking, especially between separately compiled programs. Lint takes a more global, leisurely view of the program, looking much more carefully at the compatibilities. This document discusses the use of lint...

A method for accessing text-based information using domain-specific features rather than docu-ments alone is presented. The basis of this approach is the ability to automatically extract features from large text databases, and identify statistically significant relationships or associations between those features. The techniques supporting thk approach are discussed, and examples from an appli-cation using these techniques, named the Associations System, are illustrated using the Wall Street Journal database. In this particular application, the features extracted are company and person names. The series of tests run on the Associations System demonstrate that feature extraction can be quite accurate, and that the relationships generated are reliable. In addition to conventional mea-sures of recall and precision, evaluation measures are currently being studied which will indicate the usefulness of the relationships identified, in various domain-specific contexts. 1