Sergio Vianna Fialho

Introducing self-adaptability into transaction processing

In a database system, the scheduler has the goal of synchronizing operations belonging to several concurrent transactions. In order to achieve its goal, the scheduler implements a concurrency control protocol, which may have either conservative or aggressive behavior. This paper presents a self-adaptable scheduler, called Intelligent Transaction Scheduler (ITS), which has the ability of dynamically changing its behavior (from conservative to aggressive and vice-versa) to adapt itself to the characteristics of the computing environment (e.g., the aborted transaction rate and conflicting operation rate). The proposed scheduler adapts its behavior without any human interference by using an expert system based on fuzzy logic. In order to evaluate ITS, it was applied in a Mobile Database Community (MDBC). An MDBC can be characterized as a dynamically configurable environment, since an MDBC is a dynamic collection of autonomous mobile databases, interconnected through a mobile ad hoc network (MANET). Therefore, self-adaptability plays a key role for schedulers running in dynamically configurable environments. The experimentation results show the efficiency of ITS for synchronizing transactions in MDBCs

Using an Affective Attention Focus for Improving the Reasoning Process and Behavior of Intelligent Agents

Simulations based on cognitively rich agents can become a very intensive computing task, especially when the simulated world represents a complex system. Those simulations can however benefit from optimizations coming from the way in which agents react to changes in the simulated environment. This paper presents an approach for improving the efficiency of the decision-making process of autonomous agents in a simulation. The optimization is reached by dynamically adapting the agents perception to a bounded subset of all the agents surrounding elements, which contains only the most important elements for the agent at the current time. In other words, the agent is modeled as having a dynamic focus of attention.

Dependence Maps: A Methodology for Subject Planning and Learning Assessment in Virtual Learning Environments

The use of virtual learning environments is more and more common as a support tool for classroom activities. In this case the objective of these environments is to provide pedagogic tools and methodologies to enhance the teaching-learning process. The main objective of this paper is to present the Dependence Map, a pedagogical tool that allows the teacher to plan a subject of study and its evaluation, based on educational aims, not on programmatic contents. Furthermore, this work presents a methodology, in which the Dependence Map is inserted, that includes the use of modern pedagogic theories. Also, the proposed methodology is being implemented in a software module under development, in order to be inserted in a VLE.

Introducing affective agents in recommendation systems based on relational data clustering

This paper proposes the use of a multi-agent system (MAS) with affective agents in a recommendation system based on relational data clustering. This MAS works as a mediator between the user and the data stored in the system. In the proposed system, after logging in, each user will have an affective agent, called Interface agent, for interaction purposes. This agent models the users data requests according to the users profile and its affective status, sending it to the Recommender agent, which recommends a set of map points to be visualized. The system analyzes the users feedback in order to verify whether the recommended information was satisfactory. This feedback is analyzed through the monitoring of the interaction interface.

A self-adaptable scheduler for synchronizing transactions in dynamically configurable environments

In a database system, the scheduler has the goal of synchronizing operations belonging to several concurrent transactions. The scheduler implements a concurrency control protocol, which may have either conservative or aggressive behavior. Existing database systems have schedulers with static behavior. This paper presents a self-adaptable scheduler, called Intelligent Transaction Scheduler (ITS), which has the ability of dynamically changing its behavior to adapt itself to the characteristics of the computing environment, without any human interference by using an expert system based on fuzzy logic. ITS can implement different correctness criteria, such as classical (syntactic) serializability and semantic serializability.

Ensuring Mobile Databases Interoperability in Ad Hoc Configurable Environments: A Plug-and-Play Approach

The topology of a mobile ad hoc network (MANET) may change randomly and rapidly at unpredictable time, since nodes are free to move arbitrarily. In such an environment, we may have a collection of autonomous, distributed, heterogeneous and mobile databases, denoted Mobile Database Community or MDBC. MDBC participants may join to the community as they move within communication range of one or more hosts members of the MDBC. Participants may transiently disconnect from the network due to communication disruptions or to save power. Thus, an MDBC can be characterized as an ad hoc (dynamically) configurable environment. This chapter describes an agent-based middleware, denoted AMDB (Accessing Mobile Databases), which enables such communities to be formed opportunistically and in a plug-and-play manner over mobile database in ad hoc configurable environments. AMDB has a fully distributed architecture and has the capability of exploiting physical mobility of hosts and logical mobility of database queries (transactions) across mobile hosts. Furthermore, this chapter describes a query engine for the proposed architecture and a mobile transaction processing model as well.

MovMedia: uma arquitetura fim-a-fim para suporte a aplicações multimídia móveis

New versions of SCTP protocol allow the implementation of handover procedures in the transport layer, as well as the supply of a partially reliable communication service. A end-to-end communication architecture is proposed herein, using SCTP with the session initiation protocol, SIP, besides additional protocols. This architecture is intended to handle real time multimedia applications with mobility requirements. The SDL specification language is used to specify the operation of a control module, which coordinates the operation of the system component protocols. This specification is intended to prevent ambiguities and inconsistencies in the definition of this module, assisting in the correct implementation of this architecture.

Uma arquitetura P2P para suporte a aplicações multimídia em tempo real com requisitos de mobilidade

A new SIP standard based on peer to peer paradigm allows the keeping of user localization information in a decentralized way, adding flexibility to real time mobile communications. Despite the specification of terminal mobility in P2PSIP, handover procedures in transport layer have better performance when compared with solutions used in Internet application layer. SCTP transport protocol supports terminal mobility and a partial reliability communication service. Putting together P2PSIP and SCTP extensions, an end-to-end architecture can be proposed, aimed on the support of real time multimedia applications with mobility requirements.