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Publications

Publications by HASLab

2004

Model-based collaborative filtering for team building support

Authors
Veloso, M; Jorge, A; Azevedo, PJ;

Publication
ICEIS 2004 - Proceedings of the Sixth International Conference on Enterprise Information Systems

Abstract
In this paper we describe an application of recommender systems to team building in a company or organization. The recommender system uses a collaborative filtering model based approach. Recommender models are sets of association rules extracted from the activity log of employees assigned to projects or tasks. Recommendation is performed at two levels: first by recommending a single team element given a partially built team; and second by recommending changes to a completed team. The methodology is applied to a case study with real data. The results are evaluated through experimental tests and one survey to potential users.

2004

Autonomy in an organizational context

Authors
Pacheco, O;

Publication
AGENTS AND COMPUTATIONAL AUTONOMY: POTENTIAL, RISKS, AND SOLUTIONS

Abstract
In this paper it is discussed how organizations deal with autonomy of agents that constitute them. Based on human organizations and on their legal characterization, it is proposed a normative and rolebased model for organizations (human or not), that assumes autonomy of agents as a natural ingredient. It is discussed how an organization can work without regimenting agents behavior, but simply by describing their expected (ideal) behavior (through the deontic characterization of the roles agents hold) and fixing sanctions for agents that deviate from what is expected of them. Interaction between agents is ruled through contracts that agents are free to establish between each other. A formal model, supported by a deontic and action logic, is suggested. Although this model is in a preliminary stage, it might be an useful approach to incorporate autonomy as a natural property of agents in an organizational context.

2004

Delegation in a role-based organization

Authors
Pacheco, O; Santos, F;

Publication
DEONTIC LOGIC IN COMPUTER SCIENCE, PROCEEDINGS

Abstract
In an organizational context the norms that apply to an agent depend on the roles he holds in the organization. The deontic characterization of structural roles is defined when the organization is created. But an organization is not a static entity. Among the dynamic phenomena that occur in an organization there are interactions between agents consisting in a transference of obligations or permissions from an agent to another. These kind of interactions axe called delegation. In this paper we analyze different ways in which delegation occurs in an organizational context. We argue that the concept of "agent in a role" is relevant to understand delegation. A deontic and action modal logic is used to specify this concept.

2004

Scheduling under conditions of uncertainty: A Bayesian approach

Authors
Santos, LP; Proenca, A;

Publication
EURO-PAR 2004 PARALLEL PROCESSING, PROCEEDINGS

Abstract
The efficient execution of irregular parallel applications on shared distributed systems requires novel approaches to scheduling, since both the application requirements and the system resources exhibit an unpredictable behavior. This paper proposes Bayesian decision networks as the paradigm to handle the uncertainty a scheduler has about the environment's current and future states. Experiments performed with a parallel ray tracer show promising performance improvements over a deterministic approach of identical complexity. These improvements grow as the level of system sharing and the application's workload irregularity increase, suggesting that the effectiveness of decision network based schedulers grows with the complexity of the environment being managed.

2004

A local model of eye adaptation for high dynamic range images

Authors
Ledda, P; Santos, LP; Chalmers, A;

Publication
ACM International Conference on Computer Graphics, Virtual Reality and Visualisation in Africa

Abstract
In the real world, the human eye is confronted with a wide range of luminances from bright sunshine to low night light. Our eyes cope with this vast range of intensities by adaptation; changing their sensitivity to be responsive at different illumination levels. This adaptation is highly localized, allowing us to see both dark and bright regions of a high dynamic range environment. In this paper we present a new model of eye adaptation based on physiological data. The model, which can be easily integrated into existing renderers, can function either as a static local tone mapping operator for single high dynamic range image, or as a temporal adaptation model taking into account time elapsed and intensity of preadaptation for a dynamic sequence. We finally validate our technique with a high dynamic range display and a psychophysical study. Copyright © 2004 by the Association for Computing Machinery, Inc.

2003

Semantically reliable multicast: Definition, implementation, and performance evaluation

Authors
Pereira, J; Rodrigues, L; Oliveira, R;

Publication
IEEE TRANSACTIONS ON COMPUTERS

Abstract
Semantic Reliability is a novel correctness criterion for multicast protocols based on the concept of message obsolescence: A message becomes obsolete when its content or purpose is superseded by a subsequent message. By exploiting obsolescence, a reliable multicast protocol may drop irrelevant messages to find additional buffer space for new messages. This makes the multicast protocol more resilient to transient performance perturbations of group members, thus improving throughput stability. This paper describes our experience in developing a suite of semantically reliable protocols. It summarizes the motivation, definition, and algorithmic issues and presents performance figures obtained with a running implementation. The data obtained experimentally is compared with analytic and simulation models. This comparison allows us to confirm the validity of these models and the usefulness of the approach. Finally, the paper reports the application of our prototype to distributed multiplayer games.

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