Rubens Nascimento Melo

Improving data freshness in lazy master schemes

Many distributed database applications need to replicate data to improve data availability and query response time. The two phase commit protocol guarantees mutual consistency of replicated data but does not provide good performance. Lazy replication has been used as an alternative solution in several types of applications such as online financial transactions and telecommunication systems. In this case, mutual consistency is relaxed and the concept of freshness is used to measure the deviation between replica copies. We propose two update propagation strategies that improve freshness. Both of them use immediate propagation: updates to a primary copy are propagated towards a slave node as soon as they are detected at the master node without waiting for the commitment of the update transaction. We study the behavior of our strategies and show that they improve data freshness with respect to the deferred approach.

Modeling e‐learning content

Purpose – This paper seeks to present a modeling approach for e‐learning content, describing how to structure e‐learning content and also represent it in OWL DL.Design/methodology/approach – This paper presents three different layers of information that should be considered in e‐learning and conceptual models to guide the representation of e‐learning content. This proposal is based on existing standards and experience gained in previous works. It is also shown how to structure and represent the content embedded in learning objects (LOs).Findings – Besides providing a better structuring of the e‐learning content, content reuse and exploratory navigations over content through the semantic relationships between information (mainly information objects (IOs) and conceptual units) are promoted.Research limitations/implications – A visual tool to allow a better exploration of the e‐learning content is already being developed. However, it is essential to develop optimized storing and retrieving mechanisms that wo...

The Ecobase project: database and web technologies for environmental information systems

A very large number of data sources on environment, energy, and natural resources are available worldwide. Unfortunately, users usually face several problems when they want to search and use relevant information. In the Ecobase project, we address these problems in the context of several environmental applications in Brazil and Europe. We propose a distributed architecture for environmental information systems (EIS) based on the Le Select middleware developed at INRIA. In this paper, we present this architecture and its capabilities, and discuss the lessons learned and open issues.

Increasing the Semantics of Learning Objects

The Internet has promoted several changes in the world. In this scenario, new theories, paradigms and methodologies have been discussed in the education area. In addition, as the development of learning material is expensive and time-consuming, the use of Learning Objects (LO) has been proposed for improving content reuse. However, the emphasis has been on how to describe LO, but it is not clear how to develop them. In addition, people want to satisfy their learning needs according to their personal characteristics such as knowledge background and learning style. The work presented in this paper proposes the increase of LO semantics. The idea behind our proposal is to develop LO based on a model for structuring knowledge (concepts, demonstrations and interactions) according to their context, representation and composition. This approach enables increased reusability and adaptability while providing better structured content material.

Distributed object model for collaborative CAD environments based on design history

This paper presents new concepts for distributed dynamic design environments that deal with three aspects not effectively considered by the design literature in an integrated way: design history, CAD data model, and virtual prototyping. The present work details a design history model that gives support to views of higher levels than those usually found in design journals of CAD systems. The dynamic nature of the distributed environment is provided by an innovative mechanism that is not dependent on CORBAs DII or any other specialized middleware structure. Moreover, this paper presents an effective integration of a geometry bus on the top of a communication layer with strong support to mutant distributed objects at run time.

Configurable data integration middleware system

This paper presents a new approach for generating configured and flexible middleware systems for integration of heterogeneous and distributed data. The configuration is based on the selection of an adequate set of database services components and flexibility is achieved by adopting framework techniques. A control model checks the configuration, manages the communication between components and dynamically schedules tasks. The objective is to build tailored integration middleware systems, using a minimum number of components. In addition, the use of framework allows for increased software quality and reduced development effort.

Towards a framework for corporate e-learning evaluation

The main focus of current researches is on technological and pedagogical aspects of web based learning. However, e-learning is a complex process that incorporates organizational, administrative, instructional, and technological risks. As such, various aspects should be considered for the success of e-learning. Although a lot of work has been done regarding the management, planning and implementation of e-learning, there is a lack of benchmarks to determine its success. To this end, we propose the use of an e-Learning Governance Reference Model -- eLGORM [1] that goes beyond the technological and pedagogical aspects of e-learning. In this paper we propose applying the governance principles in e-learning, based on a risk-oriented approach. We. briefly present eLGORMs processes and sub-processes and propose control standards to function as a benchmarking reference.

HEROSfe: A Framework for Heterogeneous Database Systems Integration

HEROSfw is an object-oriented framework that allows the construction of heterogeneous database management systems. This work provides an overview of HEROSfw framework, with emphasis on its components and hot spots. A detailed discussion of its implementation is also given.

An Architecture for Database Marketing Systems

Database Marketing (DBM) refers to the use of database technology for supporting marketing activities. In this paper, an architecture for DBM systems is proposed. This architecture was implemented using HEROS - a Heterogeneous Database Management System as integration middleware. Also, a DBM metamodel is presented in order to improve the development of DBM systems. This metamodel arises from the main characteristics of marketing activities and basic concepts of Data Warehouse technology. A systematic method for using the proposed DBM architecture is presented through an example that shows the architectures functionality.

A workflow-based architecture for E-learning in the Grid

Effective E-learning distributed environments should promote high cooperation. Workflow techniques can certainly contribute to such effectiveness as the creation and delivery of learning contents are typically accomplished by groups of individuals executing specific and predefined sequences of activities. Reusable learning objects (RLO or LO) also play an important role in this context as learning content is broken into smaller parts to facilitate deployment and execution assignment. Additionally, some LO may require high levels of computation as in the case of simulations in hemodynamics in a fluid mechanics course. In order to cope with such an application, we envisioned a workflow-based learning management system (LMS) using Web services as the communication infrastructure allied to the computational power of the Grid.