José Parets-Llorca

Evolving hypermedia systems: a layered software architecture

Hypermedia systems are evolutionary in nature. This paper presents SEM-HP, a model based on a semantic, systemic and evolutionary perspective, which facilitates the management of hypermedia evolution during the whole lifecycle process. Following the model the architecture of hypermedia systems can be conceived as composed of three sub-systems (conceptual, presentation and navigation) and two abstraction levels, the system level and the meta level (the first used by the reader and the second by the designer). The objective of this division is to achieve a good separation of concerns both in the development and in the evolution processes and to obtain a better understanding, thus facilitating the further development of tools.

An architecture for dynamic and evolving cooperative software agents

This paper presents an architectural model to construct cooperative and evolutionary agent-based software systems. Here, a software system is defined as one consisting of a set of agents which interact by executing actions and by determining system functionality. Because the agents need intercommunication and coordination, we propose a model that allows this communication between agents and preserves system activity. This coordination model uses a blackboard as the means of communication between the system agents. The system architecture presented is dynamic in the sense that the modelled system can evolve and be adapted to its new functions. To do this, we distinguish two levels in the architecture: the system and the metasystem levels. The system level describes the systems structure and its functionality, while the meta-system level allows us to effect changes in the system in such a way as to preserve the systems integrity and restrictions. Modifications at the system level are carried out when the developer interacts at the meta-system level. System users interact only at the system level.

A cognitive model for adaptive hypermedia systems

Like other authors, we believe that hypermedia systems, and especially the World Wide Web, can increase and improve their functionality by means of making the semantics of the information system structure explicit. In this paper, we justify the need for a cognitive model in the conception of hypermedia systems. A semantic-dynamic model is presented that provides a complete, adaptive and evolving control of the development and maintenance of hyper-documents and an understandable navigation.

A Representation of Software Systems Evolution Based on the Theory of the General System

The more commonly used software development methods assign the activities and results of the process of modification and evolution of software systems to maintenance. In this paper we present an approach to the representation of the evolution of these systems, based on Le Moignes theory of the General System, and a prototype developed in an object-oriented programming language which implements the concepts used.

Personalized Guided Routes in an Adaptive Evolutionary Hypermedia System

In this paper we describe an adaptation method for adaptive hypermedia systems, consisting in personalized guided routes for the SEM-HP model. SEM-HP is a layered, systemic, semantic and evolutionary model for the development of adaptive hypermedia systems, which adapt to the particular features and interests of each user. For evolution it uses a Metasystem, which offers to the author a set of evolutionary actions that permit the hypermedia system to evolve in a flexible and consistent way. In SEM-HP a hypermedia system is composed by four subsystems, each of which offers a different functionality to the user and to other subsystems. User adaptation is carried out by the learning subsystem, which keeps and updates an user model, which includes the user knowledge about the informational elements offered by the system, his preferences and his goal, which is to reach a certain degree of knowledge. Guided routes direct the user through the hypermedia system, so the user goal can be reached in an optimal way.

HEDES: A System Theory Based Tool to Support Evolutionary Software Systems

Software systems evolve over time. Traditional software development methods and tools support partial aspects of this evolving process. Over the last few years we have researched into theoretical evolution search models which might be applied to the development of software systems. The Theory of Systems and biology have interesting views on the evolution process, very different from genetic algorithms, which may aid in the development of software systems and CASE tools. Our aim in this paper is to present a first version of a tool (HEDES) which includes these models and implements them in an object-oriented language (VisualWorks 3.0), using first-order temporal logic as support. In addition, some lessons learnt in the development of these complex and changing tools will be outlined, especially the importance of an iterative lifecycle in object-oriented development, a high degree of cohesion of the develop- ment team and the need for flexible and rapid ways of communicating new ideas using discussion meetings, Internet facilities and development support tools.

Evolution in adaptive hypermedia systems

In this paper, the need of mechanisms of evolution in adaptive hypermedia systems is argued. Moreover, the basic characteristics of these systems are described and the user adaptation carried out in them is situated in the context of evolution models. Finally, SEM-HP, an evolutionary and adaptive hypermedia system, is presented and outlined.

A Language for Describing Complex-Evolutive Software Systems

Software systems are conceived by the developers in an iterative, recursive and evolutive way. Traditional software development methods avoid the modelling of this evolutive conception. Three years ago we began the development of a method (MEDES) which tries to model and represent this important characteristic of all the human conception activities. The main objective of this paper is to present a language which allows the description of software systems in an evolutive way, based on a model of software system which incorporates evolutive features in its structure and functioning. The language is used to make prototypes of software systems in a tool (HEDES) which implements the method.

Adaptation in an Evolutionary Hypermedia System: Using Semantic and Petri Nets

In this paper a classification of adaptive hypermedia systems is presented. Advantages and disadvantages of these systems are also discussed. As a consequence, the need of evolution is argued. An adaptive and evolving hypermedia system is presented and outlined, where the user model is formalized by means of Petri Nets. Finally, an example shows how in our proposal the user model is initialized and updated during the browsing and how adaptation is carried out over the conceptual structure of navigation.

A Formalisation of the Evolution of Software Systems

One of the most interesting and probably more difficult challenges in developing Software Systems is the modelling of their evolutionary capacity, that is to say, to gather the possibility that the Software Systems will go ahead in the future with the necessary changes to adapt to the environment using a different and new functionality. Modelling this evolution requires to have into account what kind of changes and modifications could follow and support a Software System during its life and also during its development. The evolutionary characteristics of a Software System can be approached by abstract evolutionary models, which can be further formalised. This formalisation makes operational the abstract evolutionary models and allows a kind of representation of the evolutionary process that could support the specification and mapping into concrete specification and implementation tools. These tools further allow us to obtain concrete and functional Software Systems.