Renato Cerqueira

Dynamic component gluing across different componentware systems

We present a model to support dynamic gluing of components from different componentware systems, such as CORBA, COM and Java. This model adopts a dynamic composition approach combined to the interactive facilities offered by an interpreted language. Based on this model, we define a common design for the implementation of bindings between glue languages and component systems. The proposed design provides a natural way to create dynamic bridges between different component systems. We also describe the LuaOrb system, an implementation of the proposed model that binds the interpreted language Lua to Java, CORBA and COM. With LuaOrb, Lua acts as a unifying glue language, wherein we can write code that freely use and mix components from these three component systems.

A load-balancing strategy for sort-first distributed rendering

In this paper we present a multi-threaded sort-first distributed rendering system. In order to achieve load balance among the rendering nodes, we propose a new partitioning scheme based on the rendering time of the previous frame. The proposed load-balancing algorithm is very simple to be implemented and works well for both geometry and rasterization-bound models. We also propose a strategy to assign tiles to rendering nodes that effectively uses the available graphics resources, thus improving rendering performance.

Strategies for Checkpoint Storage on Opportunistic Grids

This article evaluates several strategies for storing checkpoint data in an opportunistic grid environment, including replication, parity information, and erasure coding. We present a prototype implementation of a distributed checkpoint repository over InteGrade, a multiuniversity grid middleware project to leverage the computing power of idle shared workstations. Using this prototype, we performed several experiments to determine the trade-offs in these strategies between computational overhead, storage overhead, and degree of fault tolerance

Dynamic configuration with CORBA components

Most existing support for dynamic reconfiguration assumes that component interfaces specify input and output channels. The CORBA model, however, specifically supports a client-server architecture, with component interfaces describing only the provided services. Besides, the existing bindings for CORBA, based on static stubs, impose considerable difficulties on dynamic configuration. This paper investigates the use of the interpreted language Lua as a tool for dynamic configuration of distributed applications using CORBA components.

NCLua: objetos imperativos lua na linguagem declarativa NCL

Declarative languages are easier to learn by non-programmer professionals. On the other hand, they lack flexibility, being hard to perform tasks out of the languages scope. The power of a declarative language is leveraged when integrated with an imperative language, bringing generic computation to the language. This integration should not conflict with the principles of the declarative language, keeping a clear boundary between the two environments. This work presents the integration between the declarative NCL and imperative Lua languages, specified and developed for the middleware Ginga, part of the brazilian digital TV standard.

Multiple display viewing architecture for virtual environments over heterogeneous networks

Visualization systems that support multiple-display viewing can greatly enhance user perception. The common approach to provide multiple synchronized views uses a powerful centralized processing unit to support the rendering process on all screens. As an alternative approach, we propose a distributed architecture that supports a flexible and reliable visualization system that, while giving the users a sensation of immersion, uses a heterogeneous network of low-end graphics workstations. The proposed system ensures portability and synchronization of all displayed views.

Variable and state handling in NCL

Most time-based declarative languages have limited support for variable definition and manipulation, which causes developers to resort to imperative languages. However, a declarative language should provide a variable handling model sufficiently rich to describe a wide range of interactive applications, avoiding, as much as possible, the help of an imperative scripting language. On the other hand, the declarative simplicity should not be lost, leaving for the imperative objects more complex manipulations, with the necessary care to avoid any impact in the application’s temporal graph. Based on this principle, variables and the presentation state are handled by NCL and Ginga-NCL, as discussed in this paper. NCL is the declarative language of the Brazilian Terrestrial Digital TV System (SBTVD) supported by its middleware called Ginga. NCL and Ginga-NCL are part of ISDB standards and also of ITU-T Recommendations for IPTV services.

Using reflexivity to interface with CORBA

Most bindings to CORBA are based on the construction of stubs, which translate a language call into a CORBA invocation. The paper shows an alternative way to build a binding, using the reflexive facilities of an interpreted language. Like other CORBA bindings, this binding allows a program to manipulate CORBA objects in the same way it manipulates local objects. Unlike conventional bindings however, it is based on the CORBA Dynamic Invocation Interface, mapping its dynamic character to the dynamic type system of the language. In this way, a program has immediate access to any CORBA component, without the need of stubs or pre-defined IDL headers.

Distributed Agents Supporting Event-Driven Design Processes

In event-driven design processes, a digital mock-up is made of entities which are more than 3D, passive, virtual objects; they may be seen as part of a society of agents whose behavior emerges from their mutual interaction. This paper proposes the concept of Extended Constraint Graphs with bi-directional reactivity and one-way actions to represent reactivity and pro-activeness in a society of distributed design agents. Also, while the majority of CORBA applications in CAD systems uses static invocations, this paper presents an original approach to deal with the necessarily dynamic nature of event-driven design processes through the use of the interpreted language Lua with a CORBA binding called LuaOrb. Moreover, the use of ACIS as a Geometry Bus is presented in the context of the CORBA dynamic invocation interface.

Software Developers as Users

In view of the pervasive role played by Information Technology in contemporary life, a growing community of researchers, practitioners, and educators has been involved with human-centered computing (HCC), a fi eld of studies concerned with the integration of theories and methodologies to support the combined investigation of machines, humans, and domains of applications. Comprehensive HCC studies should then articulate technical, personal, social, and cultural factors, addressing the use of technology, its design, and development. This introductory chapter provides an overview of our incremental contribution to advance HCC studies, a suite of tools called SigniFYI . With this tool, we aim to uncover meanings inscribed in software, their origins, and consequences. We propose to identify and trace instances of consistently related objects across different segments of investigation concerning software production and use. In order to achieve this goal, we rely on semiotic engineering theory, which provides us with conceptual and methodological resources with which to obtain a coherent perspective across multiple segments of investigation. The result is a principled account of relations between the objects in each segment. Following Schön’s perspectives on refl ective practice applied to software design and development, SigniFYI stimulates researchers, professionals, and educators to think critically about what they do and how they do it and with which means and for which ends. Additionally, in research contexts, SigniFYI supports the validation of knowledge produced with interpretive research methods. As cultural, political, social, psychological, and even physical life experiences of individuals all over the world become increasingly tied to the use and effects of Information Technology (IT), a growing number of researchers, practitioners, and educators are concerned with how human values affect or can be affected by software development and use. Members of this community of interest have contributed to establishing a relatively new fi eld of studies called human-centered computing (HCC) , whose aim is to integrate various disciplines that provide us with knowledge and methods with which to search answers for the questions we ask. Theoretical and methodological integration is the key to HCC. Multiple disciplines have been contributing to the study of Computer Science and Informatics, from the more abstract ones (like mathematics and logic) to the ones that are more focused on human experience (like psychology, sociology, and design). However,