MetaComm: a meta-directory for telecommunications

Journal ArticleA great deal of corporate data is buried in network devices - such as PBX messaging/email platforms, and data networking equipment - where it is difficult to access and modify. Typically, the data is only available to the device itself for its internal purposes and it must be administered using either a proprietary interface or a standard protocol against a proprietary schema. This leads to many problems, most notably: the need for data replication and difficult interoperation with other devices and applications. MetaComm addresses these problems by providing a framework to integrate data from multiple devices into a metadirectory. The system allows user information to be modified through a directory using the LDAP protocol as well as directly through two legacy devices: a Definity ® PBX and a voice messaging system. In order to prevent data inconsistencies, updates to any system must be reflected appropriately in all systems. This paper describes how MetaComm maintains consistency when data integration is performed across several systems with no triggers and with extremely weak typing and transactional support. We also discuss implementation details and experiences

Distributed XML Design

A distributed XML document is an XML document that spans several machines. We assume that a distribution design of the document tree is given, consisting of an XML kernel-document T[f1,...,fn] where some leaves are "docking points" for external resources providing XML subtrees (f1,...,fn, standing, e.g., for Web services or peers at remote locations). The top-down design problem consists in, given a type (a schema document that may vary from a DTD to a tree automaton) for the distributed document, "propagating" locally this type into a collection of types, that we call typing, while preserving desirable properties. We also consider the bottom-up design which consists in, given a type for each external resource, exhibiting a global type that is enforced by the local types, again with natural desirable properties. In the article, we lay out the fundamentals of a theory of distributed XML design, analyze problems concerning typing issues in this setting, and study their complexity.Comment: "56 pages, 4 figures

Distributed query evaluation with performance guarantees

Partial evaluation has recently proven an effective technique for evaluating Boolean XPath queries over a fragmented tree that is distributed over a number of sites. What left open is whether or not the technique is applicable to generic dataselecting XPath queries. In contrast to Boolean queries that return a single truth value, a generic XPath query returns a set of elements, and its evaluation introduces difficulties to avoiding excessive data shipping. This paper settles this question in positive by providing evaluation algorithms and optimizations for generic XPath queries in the same distributed and fragmented setting. These algorithms explore parallelism and retain the performance guarantees of their counterpart for Boolean queries, regardless of how the tree is fragmented and distributed. First, each site is visited at most three times, and down to at most twice when optimizations are in place. Second, the network traffic is determined by the final answer of the query, rather than the size of the tree, without incurring unnecessary data shipping. Third, the total computation is comparable to that of centralized algorithms on the tree stored in a single site. We show both analytically and experimentally that our algorithms and optimizations are scalable and efficient on large trees and complex XPath queries

Um novo modelo de infra-estrutura de chaves públicas para uso no Brasil utilizando aplicativos com o código fonte aberto

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Ciência da Computação

Querying Network Directories

Hierarchically structured directories have recently proliferated with the growth of the Internet, and are being used to store not only address books and contact information for people, but also personal profiles, network resource information, and network and service policies. These systems provide a means for managing scale and heterogeneity, while allowing for conceptual unity and autonomy across multiple directory servers in the network, in a way far superior to what conventional relational or object-oriented databases offer. Yet, in deployed systems today, much of the data is modeled in an ad hoc manner, and many of the more sophisticated "queries" require navigational access. In this paper, we develop the core of a formal data model for network directories, and propose a sequence of efficiently computable query languages with increasing expressive power. The directory data model can naturally represent rich forms of heterogeneity exhibited in the real world. Answers to q..