vol. 08, no. 02

Test of distributed applications migration to Web environments

2013-04-12T13:30:04Z

Revision Journal of Computer Science & Technology; vol. 8, no. 2; http://sedici.unlp.edu.ar/handle/10915/4148 This essay is based on a previous “regression” testing knowledge, black box testing and user graphic interfaces testing. Besides, due to the fact that the testing life cycle is inside the software life cycle, the suggested focus promotes existing test cases rework, as a result of traceability of the use cases to the distributed system, the unique tests automation, integration and “regression”.

Numerical methods for engineers (fifth edition). Steven Chapra and Raymond Canale. Mc Graw Hill, 2005

2013-04-19T14:04:25Z

Revision Journal of Computer Science & Technology; vol. 8, no. 2 With this book, the same as in previous editions, Chapra and Canale intend to provide a solid training in numerical methods by means of a pleasant and attractive approach that motivates the reader to study the subject and enjoy while doing it. The authors use programming as a powerful tool to implement models and experiment with them, generating a greater enthusiasm on the reader and, as a consequence, a better understanding of the problems developed, which are applied to Engineering and Physics.

A tool for supporting the communication in distributed software development environment

2012-05-03T13:13:48Z

Articulo Journal of Computer Science & Technology; vol.8, no. 2 In the Distributed Software Development (DSD) is fundamental the use of methodologies, techniques and tools to support the communication and help teams physically distributed in the activities accomplishment. The adequate communication in the cooperative work aids in the activities management, allows the identification of flaws and deviations in the planning accomplishment, it facilitates the conflicts solution, offers support to the decision making process and also contributes to maintain the cohesion of the team. This paper presents a tool that provides synchronous, explicit and formal communication, for a Distributed Software Development Environment. This tool, named VIMEE (Virtual Distributed Meeting), allows relate to CSCW (Computer Supported Cooperative Work) and DSD areas; it defines a common workspace to manage the virtual meeting, it supports the project management and the decision making in group.

Optimizing the spatial approximation tree from the root

2012-05-08T22:00:34Z

Articulo Journal of Computer Science & Technology; vol. 8, no. 2 Many computational applications need to look for information in a database. Nowadays, the predominance of nonconventional databases makes the similarity search (i.e., searching elements of the database that are "similar" to a given query) becomes a preponderant concept. The Spatial Approximation Tree has been shown that it compares favorably against alternative data structures for similarity searching in metric spaces of medium to high dimensionality ("difficult" spaces) or queries with low selectivity. However, for the construction process the tree root has been randomly selected and the tree ,in its shape and performance, is completely determined by this selection. Therefore, we are interested in improve mainly the searches in this data structure trying to select the tree root so to reflect some of the own characteristics of the metric space to be indexed. We regard that selecting the root in this way it allows a better adaption of the data structure to the intrinsic dimensionality of the metric space considered, so also it achieves more efficient similarity searches.

Dynamic routing balancing on InfiniBand network

2012-05-03T13:13:48Z

Articulo Journal of Computer Science & Technology; vol. 8, no. 2 InfiniBand (IBA) technology was developed to address the performance issues associated with messages movement among Endnodes and computer I/O devices. However, InfiniBand is also widely deployed within high performance computing (HPC) clusters due to the high bandwidth and low message latency attributes it offers to inter-processor communication systems. An interconnection-network efficient design is mandatory because its great impact on the parallel computer performance. Therefore, a high speed routing scheme that minimizes congestion and avoids hot-spot areas should be included in the network components. We have developed Dynamic Routing Balancing (DRB), an adaptive routing mechanism that balances the communication traffic over the interconnection network. It is based on limited and load-controlled multipath expansion in order to maintain low and bounded network latency. In this work, we propose using DRB as the congestion control mechanism for InfiniBand networks. Experimentation shows that our method achieves significant performance improvement over the original InfiniBand technique which is based on message throttling. An improvement up to 66% for latency and 35% for throughput is achieved for the networks under analysis. Finally, the proposed mechanism use the management model defined in InfiniBand specs, thus full compatibility is provided.

Control Evaluation in a LVoD System Based on a Peer-to-Peer Multicast Scheme

2012-05-03T13:13:48Z

Articulo Journal of Computer Science & Technology; vol. 8, no. 2 Providing Quality of Service (QoS) in Video on Demand systems (VoD) is a challenging problem. In this paper, we analyse the fault tolerance on a P2P multicast delivery scheme, called Patch Collaboration Manager / Multicast Channel Distributed Branching (PCM/MCDB) [01]. This scheme decentralizes the delivery process between clients and scales the VoD server performance. PCM/MCDB synchronizes a group of clients in order to create local network channels to replace on-going multicast channels from the VoD server. Using the P2P paradigm supposes facing the challenge of how often peers connect and disconnect from the system. To address this problem, a centralized mechanism is able to replace the failed client. We evaluate the failure management process of the centralized scheme in terms of the overhead injected into the network and analyse the applicability of a distributed approach to managing the process. Analytical models are developed for centralized and distributed approaches. Their behaviour are compared in order to evaluate whether the distributed scheme can improve the fault management process, in terms of reducing server load and generating better scalability.

A domotic system with remote access based on web services

2012-05-03T13:13:48Z

Articulo Journal of Computer Science & Technology; vol. 8, no. 2 Domotics systems are intelligent systems for houses and apartments to control several issues as security and light or climate devices. In this work we present the development of an economic domotic system to control different electrical devices in a private house. This is achieved either from inside the building or by remote control using a regular Internet connection. In order to provide this functionality, the system includes a server that provides web services to the controlling applications in the house. This server also offers an interface that uses AJAX to optimize device handling.

Identifier Management and Resolution: Conforming the IEEE Standard for Learning Object Metadata

2012-05-03T13:13:49Z

Articulo Journal of Computer Science & Technology; vol. 8, no. 2 Uniform Resource Identifiers are an integral part of the current Architecture of the World Wide Web. This work analyzes the implications and possibilities of using Universal Resource Names as unique and persistent identifiers in systems for management of decentralized content and federated collections. Particularly, discussion focuses on applying such identifiers on the context of a learning object repository that the authors are developing at Universidad Nacional del Litoral, according to the IEEE 1484.12.1 standard for Learning Object Metadata. It is explained why Uniform Resource Locators are inadequate, and why Universal Resource Names are preferable. A standardized resolution service over Hypertext Transfer Protocol is recommended for locating resources, and usage of Uniform Resource Characteristics for accessing Learning Object Metadata is proposed. Finally, a content-negotiation mechanism for selecting the best representation among several format or language variants is outlined. The proposed naming schema provides a doubleindirection mechanism, comparable to the Human- Friendly Names approach proposed by Ballintijn, van Steen, and Tanenbaum for improving scalability and usability in naming replicated resources.

XM-Tree, a new index for web information retrieval

2012-05-03T13:13:49Z

Articulo Journal of Computer Science & Technology; vol. 8, no. 2 Web Information Retrieval is another problem of searching elements of a set that are closest to a given query under a certain similarity criterion. It is of interest to take advantage of metric spaces in order to solve a search in an effective and efficient way. In this article, we present an extension of the M-Tree index, called XM-Tree, in order to improve search results. This index allows dynamic insertion of new data, reduces search costs using pruning and precalculated distances, and uses a tolerable amount of space, which makes this index apt for the extensive and dynamic Web. The proposed extension indexes Web documents, uses L₂ as indexing distance and L_∞ as similarity criterion to solve queries. We also present experiments validating the results.

Using Exception Handling to Build Opaque Predicates in Intermediate Code Obfuscation Techniques

2012-05-03T13:13:49Z

Articulo Journal of Computer Science & Technology; vol. 8, no. 2 Microsoft's .NET Framework, and JAVA platforms, are based in a just-in-time compilation philosophy. Software developed using these technologies is executed in a hardware independent framework, which provides a full object-oriented environment, and in some cases allows the interaction of several components written in different programming languages. This flexibility is achieved by compiling into an intermediate code which is platform independent. Java is compiled into ByteCode, and Microsoft .NET programs are compiled into MSIL (Microsoft Intermediate Code). However, this flexibility comes with a price. With freeware tools available in Internet, it is quite easy to decompile intermediate codes and obtain a working, readable version of the source code. Obfuscation is the most accepted and commercially available technique that developers can use to protect their intellectual property In this work, we propose the use of try-catch mechanisms available in .NET as a way to improve the quality of one of the building blocks of obfuscation: opaque predicates.

Automatic Spot Adressing in cDNA Microarray Images

2013-04-19T14:03:09Z

Articulo Journal of Computer Science & Technology; vol. 8, no. 2 Complementary DNA (cDNA) microarrays are a powerful high throughput technology developed in the last decade allowing researchers to analyze the behaviour and interaction of thousands of genes simultaneously. The large amount of information provided by microarray images requires automatic techniques to develop accurate and efﬁcient processing. Each spot in the microarray contains the hybridization level of a single gene. One of the most important features of these images are the regularity and pseudo-periodicity implicit in the spot arrangement. In this paper, an automatic approach based on texture analysis characterization techniques is proposed to localize spots in microarray images. The method estimates the displacement vectors which characterize the texture (i.e. the spot arrangement). This is achieved by means of applying the generalized Hough transform on the 2D autocorrelation function previously segmented via morphological operations. The obtained displacement vectors are used to generate a grid template which overlaps the original image. The Root-Mean-Square-Error (RMSE) between the estimated locations and the ones computed via a semiautomatic tool is calculated to evaluate the accuracy of the process. The method yields promising results.

Analyzing and Improving Data Quality

2013-04-19T13:59:52Z

Articulo Journal of Computer Science & Technology; vol. 8, no. 2 Data quality is a research area strongly investigated during the 90’s. However, few companies in Argentina apply data quality methodologies or tools during the analysis, design or implementation phases of software development process. Developers generally use techniques to design systems such as UML without considering mechanisms for future data quality problems. In this work we propose a methodology in which the data quality is an essential part of the whole software development process. Early design decisions on data quality strongly impact on the system. Our methodology deﬁnes a set of practices to be applied on the software life cycle. In addition these practices act as a means to evaluate if systems already running fulﬁll with minimal data quality requirements.