Retrieval of textured images through the use of quantization and modal analysis

This paper proposes a new method for textured image retrieval, by the modal analysis of quantized spectral point patterns as the modal correspondence method of Shapiro and Brady, to match point sets by comparing the eigenvectors of a pairwise point proximity matrix taken from the power spectrum peaks. A variant of the Carcassoni, Ribeiro and Hancock method for performing recognition is taken into account. For choosing image features to represent an image, a quantization scheme is applied. This quantization scheme acts in the spectral space given by the Fourier transform of each image. Its goal is to find a small set which represents an image efficiently, where the most important features are presented. The proposed technique is invariant to rotation and is robust in the presence of noise and damaged images. The techniques here presented are compared, and the commonly used retrieval performance measurement—precision and recall—is used as evaluation of the query results.     

Comparing K-Means and Mean Shift Algorithms Performance Using Mahout in a Private Cloud Environment

Cloud computing has providing the possibility of services like store data, run applications and scalability of resources. The ability to measure computing resources according to request allows a great quantity of data to be stored in Data Kernels. Hadoop is a promising solution to solve problems with big sets of data. Mahout is a project developed with Hadoop that, by default, implements several grouping and classification algorithms, such as K-Means and Mean Shift, which are grouping algorithms successfully used during the last years in small databases. This paper presents a performance analysis of K-Means and Mean Shift in a standard implementation of Mahout in MapReduce distributed paradigm.     

Implementation of blocking coordinated atomic actions based on forward error recovery

The coordinated atomic action concept was proposed as a means for providing fault tolerance in complex objectoriented systems that incorporate both cooperative and competitive concurrency. This paper has two purposes: to discuss a particular implementation of this concept and to address a number of the implementation issues that are common to any experiments with this concept. Our implementation relies on a detailed set of programming conventions for the standard Ada 95 language and uses a scheme of forward error recovery incorporating concurrent exception handling and resolution. Ada 95 has a number of unique features which make it a particularly good choice for our experiments. We believe that our approach is practical and useful for many critical applications with high dependability requirements.     

Evaluating Different Strategies for Testing Software Product Lines

The Software Product Line (SPL) approach is associated with many benefits, and with some challenges too. In the SPL testing, a great challenge is the integration of test methods and techniques with the SPL engineering. To do this, some strategies have been proposed, however, they have not been properly evaluated and compared. In this paper a case study is described comparing three different test strategies: the product by product strategy that tests each product individually; an incremental strategy that tests the products reusing test cases from products previously tested; and a strategy that instantiates test data derived in the domain engineering, considering SPL commonalities and variabilities. In the study an SPL from the games domain was used, and the test data were generated from use cases. The results show that SPL oriented strategies are associated to greater percentages of reuse, and consequently, with lower effort to write test cases.     

Coordinated atomic actions as a technique for implementing distributed gamma computation

The intentions of this paper are to discuss Coordinated Atomic (CA) actions and to demonstrate how they can be used in a very new application area. We apply this concept to designing a particular case of the Gamma computational paradigm, i.e. distributed Gamma computation. Within our approach, each Gamma reaction is an action. We demonstrate how Gamma computation can be effectively implemented in conventional distributed message passing systems using CA actions. The paper discusses our design and the benefits we gain by applying CA actions: allowing as much concurrency as possible, together with guaranteeing data consistency, a better system structuring, clear separation of different system levels, and additional flexibility. This experimental design and the Java implementation allow us to conclude that CA actions are a very powerful paradigm which can be used for implementing many complex systems and, in particular, software to support some parallel computational models and paradigms.     

Consensus Algorithms on Appendable-Block Blockchains: Impact and Security Analysis

The Internet of Things (IoT) has been making people’s lives more efficient and more comfortable in the past years, and it is expected to get even better. This improvement may benefit from the use of blockchain to enhance security, scalability, reliability and auditability. Recently, different blockchain architectures were proposed to provide a solution that is better suited for IoT scenarios. One of them, called appendable-block blockchains, proposed a data structure that allows to include transactions in blocks that were already inserted in the blockchain. This approach allows appendable-block blockchains to manage large amounts of data produced by IoT devices through decoupled and appendable data structures. Nevertheless, consensus algorithms can impact throughput and latency in scenarios with large amount of produced transactions, since IoT devices can produce data very quickly (milliseconds) while these data might take some time to be included in a block (seconds). Consequently, it is important to understand the behaviour of different consensus algorithms over appendabble-block blockchain in these type of scenarios. Therefore, we adapted the appendable-block blockchain to use and compare the impact of different consensus algorithms: Practical Byzantine Fault Tolerance (PBFT), witness-based, delegated Byzantine Fault Tolerance (dBFT) and Proof-of-Work (PoW). The results show that both dBFT and PBFT can achieve fast consensus (< 150ms) in the context of appendable-block blockchains. We also present a discussion regarding attacks in each consensus algorithm to help one to choose the best solution (considering performance and security issues) for each scenario.

     

Using coordinated atomic actions to design safety‐critical systems: a production cell case study

Coordinated Atomic actions (CA actions) are a unified approach to structuring complex concurrent activities and supporting error recovery between multiple interacting objects in object‐oriented systems. This paper explains how we have used the CA action concept to design and implement a safety‐critical application. We have used the Production Cell model that was developed in the Forschungszentrum Informatik (FZI), Karlsruhe, Germany, to present a realistic industry‐oriented problem, where safety requirements play a significant role. Our design consists of two levels: the first level deals with the scheduling of CA actions, and the second level deals with the interactions between devices. Both the scheduling mechanism and the device interactions are enclosed by CA actions. Exception handling and error recovery are incorporated into CA actions in order to satisfy high safety and fault tolerance requirements. A controlling program based on our design was developed in the Java language and used to drive a graphical simulator provided by the FZI. Copyright © 1999 John Wiley & Sons, Ltd.