George Fernandez

Cognitive Scaffolding for a Web-Based Adaptive Learning Environment

On-line Web-based learning environments with automated feedback, such as WebLearn [5], present subject questions to the student and evaluate their answers to provide formative and summative assessment. With these tools, formative learning activities such as quizzes and tests are mostly pre-planned, since testing instruments are generated by selecting questions in a pre-specified manner out of question banks created for the purpose. Although this approach has been used with a significant degree of success, the real challenge to support students’ learning is to mimic what a human instructor would do when teaching: provide guided learning.

Security enforcement in the DOK federated database system

The Distributed Object Kernel (DOK) is a federated database system currently under development at the Royal Melbourne Institute of Technology. One of the issues currently under study is the development of a federated access control, as well a secure logical architecture allowing the DOK system to enforce federated security policies in the context of autonomous, distributed and heterogeneous databases. In this paper, we propose a Unified Security Model aiming for the integration of existing access control models, such as Mandatory Access Control and Discretionary Access Control, which could have been imposed on local components of a DOK application. Also, we extend the initial DOK multi-layered architecture proposed in (Tari et al. 1996) to include different types of security agents allowing the enforcement of different security functions within a federated environment. Coordination agents are responsible for maintaining a federation in a secure state by delegating the different functions to specific agents, called Task agents. By delegating the access of information within local databases to Database agents, the Task agents enforce the federated security policies using specific security procedures.

Definition and validation of design metrics for distributed applications

As distributed technologies become more widely used, the need for assessing the quality of distributed applications correspondingly increases. Despite the rich body of research and practice in developing quality measures for centralised applications, there has been little emphasis on measures for distributed software. The need to understand the complex structure and behaviour of distributed applications suggests a shift in interest from traditional centralised measures to the distributed arena. We tackles the problem of evaluating quality attributes of distributed applications using software measures. Firstly, we present a measures suite to quantify internal attributes of design at an early development phase, embracing structural and behavioural aspects. The proposed measures are obtained from formal models derived from intuitive models of the problem domain. Secondly, since theoretical validation of software measures provides supporting evidence as to whether a measure really captures the internal attributes they purport to measure, we consider this validation as a necessary step before empirical validation takes place. Therefore, these measures are here theoretically validated following a framework proposed in the literature.

Learning Objects: A Metadata Approach

Due to the convenience of being able to reuse course material, educational research in higher education has been lately focused on the provision of component-based learning, often embodied in the form of reusable Learning Objects. Ideally, it should be possible for teachers and students to select appropriate learning components from a large pool, and combine them to form a complete course. However, without a proper description of learning components from the teaching and learning point of view, it is not possible to make the sound educational decisions required for this process. In previous work we partially addressed this problem by introducing a metadata-based, formal specification of learning objectives to properly describe the educational content of a component, and we established rules and mechanisms to combine these components to form a whole course.

A federated architecture for enterprise data integration

As a result of changes in business circumstances, corporate information systems that originally have been running independently are often required to cooperate to share data or processes, particularly in organisations that are the result of, or are going through, mergers or takeovers, since in this case the existing systems have been designed for different corporate needs, and the resulting enterprise will have to face information inconsistency, heterogeneity and incompatible overlap. To effect data integration, not only must reliable mechanisms for data flow between applications be put in place, but also consistent enterprise-wide protocols and procedures to ensure the availability, security and integrity of the corporate data. The paper describes how the federated architecture described by I.K. Wijegunaratne and G. Fernandez (1998) can be used for enterprise data integration, and how this framework is being implemented for the purpose at an Australian energy company that is expanding and diversifying its operations.

A Cooperative Approach to Distributed Applications Engineering

A central problem that researchers and industry analysts are facing is how existing distributed computing technology can be used to derive the most benefits for organisations. There is no consensus as to what constitutes a good distributed application architecture, and there seems to be a lack of understanding of how the different components of a distributed application should appropriately use the communication infrastructure to interact with one another while cooperating to achieve a common goal. Although the model of processing and transactional interactions has served well the traditional applications and database arenas, we contend here that other interaction models should be contemplated when considering a distributed application architecture. In this paper we analyse the nature of communication middleware with respect to the strength of interaction induced by different modes of distributed communication. We model an enterprise as a collection of cooperating distributed application domains, deriving a federated architecture in context to support enterprise-wide distributed computing, where tightly and loosely integrated groups of applications, as well as legacy applications, can co-exist and interoperate. This approach intends to minimise the architectural mismatch between the software architecture and organisational reality. The proposed architecture has been successfully applied in Australian industry as a framework for distributed computing.

Patterns for federated architecture

An enterprise federated architecture intends to mirror the structure of the organisation, aiming to provide better support for both new and legacy applications within a distributed environment and facilitating data exchange between applications to support information integration. Under this architectural form, the organisation’s information systems are separated out into autonomous co-operating application clusters, each connected to a message-oriented federal highway acting as the vehicle for inter-domain communication. The federated approach intends to avoid unnecessary coupling (in the distributed computing sense) by grouping highly interdependent modules and applications into domains, whilst minimising the strength of inter-domain connections. This article presents how to design a distributed federated architectural form using three architectural patterns, and shows how these three patterns are to be connected to comply with the specification of the the federated form.

GeM and WeBUSE: Towards a WWW-Database Interface

This paper describes a generic metadatabase model to enable efficient browsing of structured databases by remote users in the World Wide Web environment. Existing Web-database interfaces rely on the premise that users know the database schema, and that they posses enough knowledge of the context of a schema for the correct interpretation of database semantics and query results. We propose a framework consisting of data structures, mechanisms and tools for representing a more complete description of database schemata. The Generic Meta-database (GeM) model is capable of storing, as metadata, information about databases designed using most of the popular data modelling techniques. WeBUSE (Web-Based Uniform Schema-browsing Environment) is a suite of tools which enable remote users to browse the augmented database schemata using conventional Web browsers.

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TUBE: Automated Protocol-Level Middleware Interoperation

Following changes in business processes and technology enterprises often need to interoperate protocols of heterogeneous middleware. This paper presents an automated, data-driven approach to protocol-level middleware interoperation, based on declarative descriptions of these protocols. The run-time engine of TUBE (the ubiquitous broker environment), provides a layer between application-level components and middleware that allows a degree of independence from particular middleware implementations by taking protocol descriptions and performing the necessary translations. The TUBE framework is designed to try alternatives if the searched protocol is unavailable, making it easy to deploy different types of middleware and special protocol extensions. TUBE has been implemented and successfully tested across a range of commonly used middleware, including synchronous, asynchronous, object-based, binary and text-based protocols. Key components of the system are currently in operation in a large Australian corporation.