Bayou is a replicated, weakly consistent storage system designed for a mobile computing environment that includes portable machines with less than ideal network connectivity. To maximize availability, users can read and write any accessible replica. Bayou's design has focused on supporting apphcation-specific mechanisms to detect and resolve the update conflicts that naturally arise in such a system, ensuring that replicas move towards eventual consistency, and defining a protocol by which the resolution of update conflicts stabilizes. It includes novel methods for conflict detection, called dependency checks, and per-write conflict resolution based on client-provided merge procedures. To guarantee eventual consistency, Bayou servers must be able to rollback the effects of previously executed writes and redo them according to a global senalization order. Furthermore, Bayou permits clients to observe the results of all writes received by a server, Including tentative writes whose conflicts have not been ultimately resolved. This paper presents the motivation for and design of these mechanisms and describes the experiences gained with an initial implementation of the system.

We consider the problem of storing and accessing documents (SGML and HTML, in particular) using database technology. To specify the database image of documents, we use structuring schemas that consist in grammars annotated with database programs. To query documents, we introduce an extension of OQL, the ODMG standard query language for object databases. Our extension (named OQL-doc) allows to query documents without a precise knowledge of their structure using in particular generalized path expressions and pattern matching. This allows us to introduce in a declarative language (in the style of SQL or OQL), navigational and information retrieval styles of accessing data. Query processing in the context of documents and path expressions leads to challenging implementation issues. We extend an object algebra with new operators to deal with generalized path expressions. We then consider two essential complementary optimization techniques: 1. we show that almost standard database optim...

This paper describes Lua, a language for extending applications. Lua combines procedural features with powerful data description facilities, by using a simple, yet powerful, mechanism of tables. This mechanism implements the concepts of records, arrays, and recursive data types (pointers), and adds some object-oriented facilities, such as methods with dynamic dispatching. Lua presents a mechanism of fallbacks that allows programmers to extend the semantics of the language in some unconventional ways. As a noteworthy example, fallbacks allow the user to add different kinds of inheritance to the language. Currently, Lua is being extensively used in production for several tasks, including user configuration, general-purpose data-entry, description of user interfaces, storage of structured graphical metafiles, and generic attribute configuration for finite element meshes.

s: Jan. 1992 -- Dec. 1994 ffl CTI: Current Technology Index Jan./Feb. 1993 -- Jan./Feb. 1994 ffl DAI: Dissertation Abstracts International: Vol. 53 No. 1 -- Vol. 55 No. 4 (1994) ffl EEA: Electrical & Electronics Abstracts: Jan. 1991 -- Dec. 1994 ffl P: Index to Scientific & Technical Proceedings: Jan. 1986 -- Feb. 1995 (except Nov. 1994) ffl EI A: The Engineering Index Annual: 1987 -- 1992 ffl EI M: The Engineering Index Monthly: Jan. 1993 -- Dec. 1994 The following GA researchers have already kindly supplied their complete autobibliographies and/or proofread references to their papers: Dan Adler, Patrick Argos, Jarmo T. Alander, James E. Baker, Wolfgang Banzhaf, Ralf Bruns, I. L. Bukatova, Thomas Back, Yuval Davidor, Dipankar Dasgupta, Marco Dorigo, Bogdan Filipic, Terence C. Fogarty, David B. Fogel, Toshio Fukuda, Hugo de Garis, Robert C. Glen, David E. Goldberg, Martina Gorges-Schleuter, Jeffrey Horn, Aristides T. Hatjimihail, Mark J. Jakiela, Richard S. Judson, Akihiko Konaga...

A model to query document databases by both their content and structure is presented. The goal is to obtain a query language which is expressive in practice while being efficiently implementable, features not present at the same time in previous work. The key ideas of the model are a set-oriented query language based on operations on nearby structure elements of one or more hierarchies, together with content and structural indexing and bottom-up evaluation. The model is evaluated regarding expressiveness and efficiency, showing that it provides a good trade-off between both goals. Finally, it is shown how to include in the model other media different from text.

Abstract. Social bookmark tools are rapidly emerging on the Web. In such systems users are setting up lightweight conceptual structures called folksonomies. The reason for their immediate success is the fact that no specific skills are needed for participating. In this paper we specify a formal model for folksonomies and briefly describe our own system BibSonomy, which allows for sharing both bookmarks and publication references in a kind of personal library. 1

We present a framework which allows the user to access and manipulate data uniformly, regardless of whether it resides in a database or in the file system (or in both). A key issue is the performance of the system. We show that text indexing, combined with newly developed optimization techniques, can be used to provide an efficient high level interface to information stored in files. Furthermore, using these techniques, some queries can be evaluated significantly faster than in standard database implementations. We also study the tradeoff between efficiency and the amount of indexing. 1 Introduction Database systems provide powerful features for manipulating large quantities of data. They do not, however, provide access to data stored in files outside the database system. A large portion of the information in a computerized environment resides in the file system, and not in databases. This includes, in particular, semi-structured textual information such as: electronic documents, pro...

Process Support Systems (PSSs) support business organizations in modeling, improving, and automating their business process. Thanks to their ability in enacting process models, they can be used to guide people in performing their daily work and to automate the repetitive tasks that do not require human intervention. Given these potential benefits, it is surprising to observe that PSSs are not widely adopted. This is especially true in case of highly flexible and human-intensive processes such as design processes in general and software processes in particular. This fact can be explained by observing that currently available PSSs do not fulfill some crucial needs of modern business organizations. One of their major drawbacks is that they do not offer adequate mechanisms to cope with unforeseen situations. They are good at supporting business processes if all proceeds as expected, but if an unexpected situation is met, which would require to deviate from the process model, they often bec...

Bibliographic records freely available on the Internet can be used to construct a highquality, digital finding aid that provides the ability to discover paper and electronic documents. The key challenge to providing such a service is integrating mixed-quality bibliographic records, coming from multiple sources and in multiple formats. This thesis describes an algorithm that automatically identifies records that refer to the same work and clusters them together; the algorithm clusters records for which both author and title match. It tolerates errors and cataloging variations within the records by using a full-text search engine and an n-gram-based approximate string matching algorithm to build the clusters. The algorithm identifies more than 90 percent of the related records and includes incorrect records in less than 1 percent of the clusters. It has been used to construct a 250,000-record collection of the computer science literature. This thesis also presents preliminary work on aut...

In this paper we describe a technique called operation-based update propagation for efficiently transmitting updates to large files that have been modified on a weakly connected client of a distributed file system. In this technique, modifications are captured above the file-system layer at the client, shipped to a surrogate client that is strongly connected to a server, re-executed at the surrogate, and the resulting files transmitted from the surrogate to the server. If re-execution fails to produce a file identical to the original, the system falls back to shipping the file from the client over the slow network. We have implemented a prototype of this mechanism in the Coda File System on Linux, and demonstrated performance improvements ranging from 40 percents to nearly three orders of magnitude in reduced network traffic and elapsed time. We also found a novel use of forward error correction in this context.