Many distributed systems for wide­area networks can be built conveniently, and operate efficiently and correctly, using a weak consistency group communication mechanism. This mechanism organizes a set of principals into a single logical entity, and provides methods to multicast messages to the members. A weak consistency distributed system allows the principals in the group to differ on the value of shared state at any given instant, as long as they will eventually converge to a single, consistent value. A group containing many principals and using weak consistency can provide the reliability, performance, and scalability necessary for wide­area systems. I have developed a framework for constructing group communication systems, for classifying existing distributed system tools, and for constructing and reasoning about a particular group communication model. It has four components: message delivery, message ordering, group membership, and the application. Each component may have a different implementation, so that the group mechanism can be tailored to application requirements. The framework supports a new message delivery protocol, called timestamped anti­entropy, which provides reliable, eventual message delivery; is efficient; and tolerates most transient processor and network failures. It can be combined with message ordering implementations that provide ordering guarantees ranging from unordered to total, causal delivery. A new group membership protocol completes the set, providing temporarily inconsistent membership views resilient to up to k simultaneous principal failures. The Refdbms distributed bibliographic database system, which has been constructed using this framework, is used as an example. Refdbms databases can be replicated on many different sites, using the group communication system described here.

: Full-text retrieval systems typically use either a bitmap or an inverted file to identify which documents contain which words, so that the documents containing any combination of words can be quickly located. Bitmaps of word occurrences are large, but are usually sparse, and thus are amenable to a variety of compression techniques. Here we consider techniques in which the encoding of each bitvector within the bitmap is parameterised, so that a different code can be used for each bitvector. Our experimental results show that the new methods yield better compression than previous techniques. Categories and Subject Descriptors: E.4 [Coding and Information Theory]: Data compaction and compression; H.3.2 [Information Storage]: File organisation . Keywords: Full-text retrieval, data compression, document database, Huffman coding, geometric distribution, inverted file. 1 Introduction Full-text retrieval systems are used for storing and accessing document collections such as newspaper a...

Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) Program Office plays a key part in helping NASA maintain this important role. The NASA STI Program Office is operated by Langley Research Center, the lead center for NASA's scientific and technical information. The NASA STI Program Office provides access to the NASA STI Database, the largest collection of aeronautical and space science STI in the world. The Program Office is also NASA's institutional mechanism for disseminating the results of its research and development activities. These results are published by NASA in the NASA STI Report Series, which includes the following report types:

This paper describes an Arabic formatting system that is able to format multilingual scientific documents, containing text in Arabic or Persian, as well as other languages, plus pictures, graphs, formulae, tables, bibliographical citations, and bibliographies. The system is an extension of ditroff/ffortid that is already capable of handling Hebrew in the context of multilingual scientific documents. ditroff/ffortid itself is a collection of pre- and postprocessors for the UNIX ditroff (Device Independent Typesetter RunOFF) formatter. The new system is built without changing ditroff itself. The extension consists of a new preprocessor, fonts, and a modified existing postprocessor. The preprocessor transliterates from a phonetic rendition of Arabic using only the two cases of the Latin alphabet. The preprocessor assigns a position, stand-alone, connectedprevious, connected-after, or connected-both, to each letter. It recognizes ligatures and assigns vertical positions to the optional diacritical marks. The preprocessor also permits input from a standard Arabic keyboard using the standard ASMO encoding. In any case, the output has each positioned letter or ligature and each diacritical mark encoded according to the font’s encoding scheme. The fonts

This paper describes a system for formatting documents consisting of text written in languages printed in three different directions, left-to-right, right-to-left, and top-to-bottom. For example, this paper is such a document because it contains text written in English, Hebrew, Japanese, and Chinese. The system assumes that the input is in the order in which the text is read aloud, and it produces output in which each language is printed in its own correct direction, but for which a human cognizant of the reading conventions will reproduce the input order. The system consists of three major pieces of software: Ossana and Kernighan's ditroff for formatting text consisting of only left-to-right or unidirectional text, Buchman and Berry's ffortid for rearranging right-to-left language text occurring in ditroff output to be printed from right to left, and a new program bditroff for rearranging top-tobottom text occurring in ditroff output to be printed from top to bottom.

Heath O'Connell hoc@ slac.stanford.edu Stanford Linear Accelerator Center, Stanford University, Stanford CA, USA The Universal Preprint Service (UPS) Prototype was developed in preparation of the first meeting of the UPS initiative - later renamed the Open Archives initiative - held in Santa Fe, New Mexico October 21-22, 1999. The purpose of the meeting was to generate discussion and concensus regarding the interoperability of publicly available scholarly information archives. The invitees represented several renown e-print and report archive initiatives, as well as organizations with an interest in digital libraries and the transformation of scholarly communication. The central goal of the meeting was to agree on recommendations that would make the creation of end-user services - such as scientific search engines, recommendation systems and linking systems - for data originating from distributed and dissimilar archives easier. To facilitate the discussions, the UPS Prototype was constructed as a proof-of-concept of a multi-discipline digital library of publicly available scholarly material. The UPS Prototype harvested its nearly 200,000 records from several different archives and created an attractive end-user environment. As such, the UPS Prototype was a demonstration vehicle for other digital library technologies, such as intelligent digital objects (buckets) and reference linking services (SFX). The paper touches on their applicability in an e-print environment.

flo is a language for including flowcharts into documents typeset using the UNIX™ ditroff. A basic flowchart can be created with minimal effort by inputting only the basic algorithm written in a Pascal-like notation. The example below illustrates the general capability of flo. The flowchart to the left is obtained from the input to the right.

40 1. A comparison of existing text formatters 41 2. Editing structured text 42 3. The user's view of the Alpha text formatting system 42 4. The Alpha document description language 44 5. Organization of the Alpha system 46 6. The tree editor 47 7. Minimization of re-formatting 51 8. Traversing the document tree 52 9. Efficiency and performance 54 10. Conclusions and applications 56 References 57 Unix Manual Pages 59 ALPHA(9.1) 60 DITPS(9.1) 62 WSHELL(9.1) 64 WORDY(9.1) 68 FISHFONT(9.5) 25th October 1988 Page 1 Foreword Page 2 25th October 1988 "Who often reads, will sometimes wish to write." --- George Crabbe The subject or discipline of text formatting, and its more pretentious big brother desktop publishing, are the sirens of modern computer science. Many researchers in all areas of computer science have been diverted from their "serious" work by the thought of building a computer-based system for turning the contents of a computer file into printed words on a sheet of paper. I...

We present the Smart Object, Dumb Archive (SODA) model for digital libraries (DLs), and discuss the role of metadata in SODA. The premise of the SODA model is to "push down" many of the functionalities generally associated with archives into the data objects themselves. Thus the data objects become "smarter", and the archives "dumber". In the SODA model, archives become primarily set managers, and the objects themselves negotiate and handle presentation, enforce terms and conditions, and perform data content management. Buckets are our implementation of smart objects, and da is our reference implementation for dumb archives. We also present our approach to metadata translation for buckets. 1.0 INTRODUCTION The observation that motivated the Smart Object, Dumb Archive (SODA) model for digital libraries (DLs) is that data objects are more important than the archives that hold them. Many DL systems and protocols are reaching a level of complexity where DL-interoperability and object mob...

Abstract not found