Band 8, Heft 1

Effect systems refine types with information about the behaviour of programs. They have been used for many purposes, such as optimizing programs, determining resource usage, and finding bugs. So far, however, work on effect systems has largely concentrated on call-by-value languages. We consider the problem of designing an effect system for a lazy language. This is more challenging because it depends on the ability to locate the first use of each variable. Coeffect systems, which track contextual requirements of programs, provide a method of doing this. We describe how to track variable usage in a coeffect system that can be instantiated for different reduction strategies, including call-by-need. We then add effects to the result, allowing work that has been done on effect systems for call-by-value languages to be applied to lazy languages.

We define a computable function f from positive integers to positive integers. We formulate a hypothesis which states that if a system S of equations of the forms x i · x j = x k and x i + 1 = x i has only finitely many solutions in non-negative integers x 1 , . . . , x i , then the solutions of S are bounded from above by f (2n). We prove the following: (1) the hypothesis implies that there exists an algorithm which takes as input a Diophantine equation, returns an integer, and this integer is greater than the heights of integer (non-negative integer, positive integer, rational) solutions, if the solution set is finite; (2) the hypothesis implies that the question of whether or not a given Diophantine equation has only finitely many rational solutions is decidable by a single query to an oracle that decides whether or not a given Diophantine equation has a rational solution; (3) the hypothesis implies that the question of whether or not a given Diophantine equation has only finitely many integer solutions is decidable by a single query to an oracle that decides whether or not a given Diophantine equation has an integer solution; (4) the hypothesis implies that if a set M ⊆ N has a finite-fold Diophantine representation, thenMis computable.

Loops are repetitive control structures in programming languages. They are used extensively in many algorithms. The for-loop and while-loop exist, where the former is repeated a number of times while the latter is repeated until a condition is met. Some have asked if re-arranging loops in certain ways can change a program’s speed to produce machine-independent optimisation. Therefore, this research sought to find out if there is any speed difference in a single loop of computations and a loop with an inner loop of same computations. Greater focus is on inner for-loop. The research used a comparative study method in order to evaluate the primary data obtained from running several tests in four popular programming languages: C, C#, Python and R. The Python implementations were further tested on Ubuntu 16 for comparison with results from Windows 10. Results established that, across all languages, there were more computations performed per unit time with an inner for-loop than no inner loop, meaning, given the same number of computations to perform, a loop with an inner for-loop will finish faster. The inner while-loop didn’t perform so well, though. This study will help developers in making better choices with programming language and style.

This paper proposes the mathematical modeling and robust control algorithms for linear belt system with the help of sliding mode control approach. Due to the elasticity of the belt, the presence of frictions, and the un-modeled dynamics, conventional controllers cannot provide precise position control of carriage. Dealing with this kind of system, a robust controller is needed and the chattering-free sliding mode control (SMC) approach is used to design the robust controller. A belt stretching estimator is also incorporated into the control law. Simulations show that the system is free from chattering and robust to disturbances. The reference tracking position is performed with the minimal errors to an extent that can be considered negligible. The time for reaching the reference tracking position is very fast. The system is safe for all mechanical and electrical devices.

Many modern distributed services are deployed in dynamic systems. Cloud services are an example. They are expected to provide service to a potentially huge amount of users and may require a wide geographical deployment in multiple data centres. Their service processes vary in volume in accordance with workload variations, showing an adaptive behaviour in order to minimise economical costs. Dynamic distributed systems may be classifed considering two axes: (a) the number of processes that compose the system, and (b) the diameter of the networking graph that interconnects those processes. Other important features of dynamic systems can be derived from these two characteristics, e.g., their attainable synchrony. We analyse the level of synchrony that may be achieved in each dynamic system class and revise the existing techniques for transforming an initially asynchronous large dynamic system into another one with a higher synchrony level. With this, a larger set of problems may be handled in dynamic distributed systems. This facilitates the implementation and provision of additional services in those systems.

Computational complexity is a characteristic of almost all Lesk-based algorithms for word sense disambiguation (WSD). In this paper, we address this issue by developing a simple and optimized variant of the algorithm using topic composition in documents based on the theory underlying topic models. The knowledge resource adopted is the English WordNet enriched with linguistic knowledge from Wikipedia and Semcor corpus. Besides the algorithm’s eficiency, we also evaluate its efectiveness using two datasets; a general domain dataset and domain-specific dataset. The algorithm achieves a superior performance on the general domain dataset and superior performance for knowledge-based techniques on the domain-specific dataset.

We demonstrate several ways to use morphological word analogies to examine the representation of complex words in semantic vector spaces. We present a set of morphological relations, each of which can be used to generate many word analogies. 1. We show that the difference-vectors for pairs which have the same relation to each other are similarly aligned. 2. We suggest that addition of difference-vectors is a useful phrase-building operator. 3. We propose that pairs in the same relation may have similar relative frequencies. 4. We suggest that homographs, which necessarily have the same semantic vectors, can sometimes be separated into different vectors for different senses, using frequency estimates and alignment constraints obtained from word analogies. 5. We observe that some of our analogies seem to be parallel, and might be combined. We use Arabic words as a case study, because Arabic orthography includes verb conjugations, object pronouns, definitive articles, possessive pronouns, and some prepositions in single word-forms. Therefore, a number of short phrases, built up of easily perceived constituents, are already present in stock semantic spaces for Arabic available on the web. Similar phrases in English would require including bigrams or trigrams as lemmas in the word embedding, although English derivational morphology allows for other relationships in standard semantic spaces which Arabic does not, for example negation. We make our corpus of morphological relations available to other researchers.

Data mining is a popular research area that has been studied by many researchers and focuses on finding unforeseen and important information in large databases. One of the popular data structures used to represent large heterogeneous data in the field of data mining is graphs. So, graph mining is one of the most popular subdivisions of data mining. Subgraphs that are more frequently encountered than the user-defined threshold in a database are called frequent subgraphs. Frequent subgraphs in a database can give important information about this database. Using this information, data can be classified, clustered and indexed. The purpose of this survey is to examine frequent subgraph mining algorithms (i) in terms of frequent subgraph discovery process phases such as candidate generation and frequency calculation, (ii) categorize the algorithms according to their general attributes such as input type, dynamicity of graphs, result type, algorithmic approach they are based on, algorithmic design and graph representation as well as (iii) to discuss the performance of algorithms in comparison to each other and the challenges faced by the algorithms recently.

This paper presents numerical experiments with assorted versions of parallel LU matrix decomposition algorithms (Gauss and Crout algorithm). The tests have been carried out on the hardware platform with fourcore Skylake processor featuring hyperthreading technology doubling virtually core number. Parallelization algorithms have been implemented with the aid of classic POSIX threads library. Experiments have shown that basic 4-thread acceleration of all parallel implementations is almost equal to the number of threads/processors. Both algorithms are worth considering in real-world applications (Florida University collection). Gauss algorithm is a better performer, with respect to timing, in the case of matrices with lower density of nonzeros, as opposed to higher density matrices. The latter are processed more efficiently with the aid of Crout algorithm implementation.

Whether or not word sense disambiguation (WSD) can improve information retrieval (IR) results represents a topic that has been intensely debated over the years, with many inconclusive or contradictory conclusions. The most rarely used type of WSD for this task is the unsupervised one, although it has been proven to be beneficial at a large scale. Our study builds on existing research and tries to improve the most recent unsupervised method which is based on spectral clustering. It investigates the possible benefits of “helping” spectral clustering through feature selection when it performs sense discrimination for IR. Results obtained so far, involving large data collections, encourage us to point out the importance of feature selection even in the case of this advanced, state of the art clustering technique that is known for performing its own feature weighting. By suggesting an improvement of what we consider the most promising approach to usage of WSD in IR, and by commenting on its possible extensions, we state that WSD still holds a promise for IR and hope to stimulate continuation of this line of research, perhaps at an even more successful level.

The paper considers the problem of developing rational methods for the creation of a framework (a plan, execution timetable) of parallel programs for real parallel computing systems. To solve this problem, a software environment (software stand) has been developed that allows implementing different strategies for building a framework for parallel programs and assessing the quality of these strategies. The built-in script Lua programming language is used to increase the flexibility of modeling and optimization capabilities. Results of applying some of the proposed strategies for constructing rational plans for parallel programming are outlined.

LIRKIS CAVE is a unique immersive virtual reality installation with a compact cylinder-based construction and a high-quality stereoscopic video output rendered on twenty 55” Full HD LCD panels. While the video output of the CAVE provides a high level of immersion to a virtual world, its original implementation of peripherals support had a negative impact because of a limited number of supported devices and certain performance issues. In this paper we describe a new, distributed, peripheral devices support implementation for the LIRKIS CAVE, which solves the performance issues and allows for ease of integration of new input devices into the CAVE. We also present a successful integration of a special input device, the Myo armband,which allows a natural and unobtrusive gesture-based control of virtual environments. The integration includes a newly developed control and monitoring application for the Myo, called MLCCS, which utilization is not limited to CAVE systems or virtual reality applications.

This paper deals with a model of the telegraph line that consists of system of ordinary differential equations, rather than partial differential telegraph equation. Numerical solution is then based on an original mathematical method. This method uses the Taylor series for solving ordinary differential equations with initial condition - initial value problems in a non-traditional way. Systems of ordinary differential equations are solved using variable order, variable step-size Modern Taylor Series Method. The Modern Taylor Series Method is based on a recurrent calculation of the Taylor series terms for each time interval. The second part of paper presents the solution of linear problems which comes from the model of telegraph line. All experiments were performed using MATLAB software, the newly developed linear solver that uses Modern Taylor Series Method. Linear solver was compared with the state of the art solvers in MATLAB and SPICE software.

The foundations for traditional data analysis are Online Analytical Processing (OLAP) systems that operate on multidimensional (MD) data. The Resource Description Framework (RDF) serves as the foundation for the publication of a growing amount of semantic web data still largely untapped by companies for data analysis. Most RDF data sources, however, do not correspond to the MD modeling paradigm and, as a consequence, elude traditional OLAP. The complexity of RDF data in terms of structure, semantics, and query languages renders RDF data analysis challenging for a typical analyst not familiar with the underlying data model or the SPARQL query language. Hence, conducting RDF data analysis is not a straightforward task. We propose an approach for the definition of superimposed MD schemas over arbitrary RDF datasets and show how to represent the superimposed MD schemas using well-known semantic web technologies. On top of that, we introduce OLAP patterns for RDF data analysis, which are recurring, domain-independent elements of data analysis. Analysts may compose queries by instantiating a pattern using only the MD concepts and business terms. Upon pattern instantiation, the corresponding SPARQL query over the source data can be automatically generated, sparing analysts from technical details and fostering self-service capabilities.

This paper presents a new method for forecasting a load of individual electricity consumers using smart grid data and clustering. The data from all consumers are used for clustering to create more suitable training sets to forecasting methods. Before clustering, time series are efficiently preprocessed by normalisation and the computation of various model-based time series representation methods. Final centroid-based forecasts are scaled by saved normalisation parameters to create the forecast for every consumer. Our method is compared with the approach that creates forecasts for every consumer separately. Evaluation and experiments were conducted on three smart meter datasets from residences of Ireland and Australia, and factories of Slovakia. The achieved results proved that our clustering-based method improves forecasting accuracy mainly for residential consumers.We can also proclaim that it can be found such time series representation and clustering setting that will our forecasting method perform more accurately than fully disaggregated approach. Our method is also more scalable since it is necessary to train the model only on clusters and not for every consumer separately

In this paper we design novel techniques for manual domain usability evaluation. Domain usability is the aspect of a particular user interface that relates to its terminology, hierarchy of terms, feature descriptions and icons, used language and consistency. However, domain usability is often neglected not only by software developers, but also by many researchers. The design of formal means to evaluate existing user interfaces would aid the development of better, domain-usable user interfaces. We designed six qualitative evaluation techniques and one formal evaluation technique based on System Usability Scale (SUS). To show the viability of the designed techniques, we demonstrate each of them in the domain of gospel music. Two of the techniques were used to experimentally verify the impact of specific domain usability aspects on usability and user experience. In this paper we also focus on the equality of the domain usability aspects with the goal of designing domain usability metrics. The preliminary design of the metrics is also presented in this paper and areas of future research are suggested.

The paper is motivated by critical demand for experts and scientists working in areas of mathematical modeling, simulations, big data techniques and who are familiar with management of HPC systems from user and administrator point of view. We created a new course entitled “HPC system management”. Our goal is focused on students to provide them with knowledge and understanding of complex problem of the HPC system management concerning job scheduling. Important fact is that the job scheduling problem is an NP-complete problem. Next objective of our course is to educate skilled experts, who are able to design and implement programs, scripts and models doing job management to solve specific parts of this complex problem. The course is innovative from several points of view. Our new approach lies in specific content, which is oriented to the HPC system management in contrast to existing courses, which are usually focused on development of HPC applications. Also we developed and provide new education methodology in a form of scientific project, which decomposes the complex problem into subproblems and subsequently brings together solutions to the subproblems to form united model. New education methodology is focused on generation of (pseudo-) optimal jobs schedule using data from real systems. The huge volume of used data leads to ideas and methodologies of problem solving, which are suitable for problems not solvable in polynomial time. Educational methodology also contains implementation of a job scheduling simulator. The paper presents a pilot course, in which students explore various scheduling algorithms and research their properties with the use of data gained from NorduGrid

This paper describes the design of a testing environment for massive assessment of assignments for Android application programming courses. Specific testing methods and tool suggestions are continuously consulted with Wirecard company, dedicated to the development of mobile applications. The paper also analyzes the most common mistakes of students and suggests ways to uncover them through tests. Based on these, it creates tests, compares the performance of the emulator and real device tests, and the proposed tools are partially retrospectively tested on assignments from the previous run of a particular Android application programming course. From partial results the paper suggests changes for the course in relation to the testing environment and deploys it in the background of the course alongside the manual evaluation. It describes testing experience, analyzes the results and suggests changes for the future

In this paper, the development of Extensible Markup Language (XML) schema of newly proposed Human body description format (HBDF) is proposed and further, the software and hardware solution for processing and acquiring the anthropometric parameters of the human body is presented. The analysis covers information on the HBDF format and specific measurement procedures that are associated with the format and together form a coherent structure for the recording of such data. The structure of the format itself is implemented as XML schema, determining the content of XML outputs. Experimental software solution is designed and proves valid in the examination of HBDF structure. The experimental hardware is proposed to introduce new approach to measurement using the physical real-world device. Proposed hardware solution also implements HBDF structure. Schema ensures the data coherency and integrity,while the proposed solution ensures the import, operation, and export of data. The XML schema was experimentally tested as a part of multiple research projects.

Nowadays, wireless optical systems are very popular because they offer a a lot of advantages including high speed transmission, high security levels, and low maintenance costs. One of these wireless optical systems is Free Space Optics (FSO). However, their primary drawback relates to the type of transmission medium used. Atmospheric channel is chosen to be the transmission medium for FSO systems. The resulting attenuation relates with all inhomogeneities that occur in the atmosphere. Concentration of water particles represents inhomogeneities which increase the levels of attenuation. Weather conditions are characterized by speciffc concentration of these particles. Visibility is one of the most crucial parameters for FSO communication. It is very important to monitor this parameter in order to switch between primary optical line and backup secondary Radio Frequency (RF) line. The focus of this paper is to analyze and evaluate visibility measurement in FSO system deployed in TUKE (Technical University of Kosice) campus. The measurement of different weather parameters for this system is triggered on TUKE. The Switching method is based on monitoring visibility as the primary parameter. Different measurement approaches provide different processing speeds. Faster and more accurate switching ensures stable system without disruption.

We propose a resource-oriented architecture of a rational agent for a network intrusion detection system. This architecture describes the behavior of a rational agent after detection of unwanted network activities. We describe the creation of countermeasures to ward off detected threats. Examples are created based on the proposed architecture, describing the process during a rational agent detection. We have described these examples by linear BDI logic behavioral formulæ, that have been proven by Gentzen sequent calculus.