An algorithm is demonstrated that finds an ordinary intersection in an arrangement of $n$ lines in $\mathbb{R}^2$, not all parallel and not all passing through a common point, in time $O(n \log{n})$. The algorithm is then extended to find an ordinary intersection among an arrangement of hyperplanes in $\mathbb{R}^d$, no $d$ passing through a line and not all passing through the same point, again, in time $O(n \log{n})$. Two additional algorithms are provided that find an ordinary or monochromatic intersection, respectively, in an arrangement of pseudolines in time $O(n^2)$.
This paper proposes a theoretical framework for separation of concerns in the formal specification of reactive and real-time systems. This framework consists of the syntax and the semantics of three languages (and all meaningful combinations thereof) that each address a separate concern. The first language, Gamma (a variant of an exist- ing language) is used to define the functionality of a system (by means of a set of basic data transformations). Our additions are a simple language of intervals specifying timing- properties of basic transformations and a language (called Schedules) for specifying the coordination of the basic Gamma transformations. Each of these languages formally mod- els a separate aspect of a system and statements in these languages can be reused, changed or analyzed in their own right. Our key contribution is that we provide a formal framework in which different combinations of aspects have a well-defined semantics. ACM CCS Categories and Subject Descriptors: F.3 (Logics and Meanings of Pro- grams); D.3.1 (Formal Definitions and Theory); D.1.3 (Concurrent Programming)
A workhorse in verification of a concurrent system is generating and analysing its state space, a graph of its reachable states. Based on simple information-theoretical arguments and complexity theory, we contribute towards a general understanding of what is involved in making state space -based verification efficient in practice. Using concrete methods from the literature as examples, we demonstrate that the more information one is willing to throw away when constructing a reduced state space, the better are the possibilities of obtaining good reduction. It is thus worthwhile to analyse what kind of information is really needed to solve a verification problem. We also discuss what symmetries or implicit representations, such as binary decision diagrams, can and cannot do.
Nowadays, JavaScript is the language for developing dynamic websites. Previously, several guidelines were published about how to write efficient JavaScript code. Our research focuses on whether programmers should still adhere to these guidelines or they can rely on the state-of-the-art JavaScript execution engines to achieve good performance results. In this paper, we present the experiments where we validate programming guidelines for JavaScript execution performance across multiple state-of-the-art web browsers. We present our observations, and conclude that the importance of guidelines does not decrease with the introduction of JIT technology.
Code cloning is often considered as a bad practice in programming, especially from the point of view of maintenance. In this paper we present the results of an empirical study which revealed inverse correspondence between cloning and coupling. Since low coupling is conventionally regarded favourable for maintenance, this finding appears slightly surprising at first sight. In this paper we study the possible benefits of code cloning. Based on a theoretical structural analysis of the effect of cloning, we draw conclusions on the actual, restricted ways cloning is applied in practice.
Generalization is common in object-oriented modeling. It would be useful in many situations also as a language mechanism, reverse inheritance, but there have been only few detailed proposals for that. This paper defines reverse inheritance as a true inverse of ordinary inheritance, without changing anything else in the language that is extended. Eiffel is perhaps the most suitable language for that purpose because of its flexible inheritance principles. Moreover, there exists good previous work on Eiffel, on which we have built. We describe the most important aspects of our extension, whose details proved to be more difficult than we had assumed. It would be easier if some modifications were made to Eiffel's ordinary inheritance, or if one designed a new language. We also briefly mention our proof-of-concept implementation in which reverse inheritance is changed to ordinary inheritance by automatic transformations, and thus no compiler modifications are needed.
Magnetic Resonance in ChemistryVolume 32, Issue S1 p. S1-S1 Guest Editor's Foreword Guest editor's foreword Wiebren S. Veeman, Wiebren S. Veeman Physical Chemistry, Gerhard-Mercator-Universität-GH-DuisburgSearch for more papers by this author Wiebren S. Veeman, Wiebren S. Veeman Physical Chemistry, Gerhard-Mercator-Universität-GH-DuisburgSearch for more papers by this author First published: December 1994 https://doi.org/10.1002/mrc.1260321302AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume32, IssueS1Special Issue: NMR in Polymer ChemistryDecember 1994Pages S1-S1 RelatedInformation
It is an honour to be invited to be Guest Editor of the ISJ for this Special Holographic edition particularly when approaching the end of my career primarily in optical metrology. I first became involved at AWRE Aldermaston using high speed/ ultra high speed photography. Later, when with CEGB research laboratories, I collaborated with the University of St Andrews on early argon laser development with a view to applying it to several imaging situations. My interest in holography was aroused during the mid 60’s when I attended a lecture by Professor Gabor. One of my then current problems was recording water droplets forming in steam turbines. I saw holography’s potential as a tool of measurement for such applications. Around 1967 I acquired a small pulsed ruby laser produced by Barr and Stroud; it proved an effective, if limited, tool for holography. However, I realised that pulsed holography was a possible solution for ‘‘in reactor’’ inspection in biologically hostile areas. At that time it was not possible to obtain a powerful portable laser for applications under the arduous conditions imposed by in-reactor applications. In association with J. K. Lasers we funded and set about developing such a system from a prototype which J K Lasers had constructed for Nick Phillips. This laser finally proved commercially a very popular. Through EU sponsorship I enjoyed a Chair at the University of Rome for three years applying holographic techniques to the restoration of ancient artefacts. I also had the opportunity to co-operate with several artists using pulsed lasers; the cover picture is one example of this work. The 90’s were spent in the USA where I was funded for the development of NDT using both holographic interferometry and acoustics/laser Doppler imaging techniques. The team I lead took the concept of a portable holographic ruby laser/camera to what must be its ultimate. More recently I was appointed to an Honorary Chair at the University of Aberdeen. Over the years much of my work has been published in this journal. My full publications list can be seen: https:// docs.google.com/viewer?a5v&pid5explorer&chrome5 true&srcid50B_Lensk3qxZTZTNiYWE5YzgtNDk0O S00MzlmLThiNmItYzFmNGZjYjVkMjQ1&hl5en John M Webster PhD, MinstP, C.Phys, C.sci. websterjmphysics@gmail.com
International Conferences hhElectronic Processes in Organic Materialsii (ICEPOM) are organized periodically in the different regions of Ukraine to improve the international cooperation of scientists in the field of organic materials. Prof. Martin Pope is the initiator of these conferences series. The 7th International Conference hhElectronic Processes in Organic Materialsii (ICEPOM-7) has been held in Lviv (Ukraine) on May 26– 30, 2008. The objective of the conference is to discuss physical phenomena and processes in organic materials and at their interfaces with other materials as well as prospects of their practical applications.
Agile methods have gained popularity in the software industry. A backlog, which is, roughly, a prioritized list of things to be done, is used as a means of management of development. However, one particular challenge is that a backlog does not provide information beyond isolated backlog items, e.g., especially that of composed entities, such as the product in the whole. We describe the Featback method, which provides information that the existing means do not directly provide, especially of composed entities. The information is based on analyses using the concepts from an integrated backlog and feature model, thus integrating structural and developmental information. Justification is provided by the definition specifications for analyses and by using an expository instantiation of a running example for the Featback method.
We consider the problem of tracking a mobile user moving through a cellular network using node queries that provide information as to last time the user visited the node. Queries are executed in rounds, each round may involve queries to many nodes simultaneously, and the user may move at the same time that queries are performed. The cost measures considered are the number of rounds required to find the user and the total number of queries made during the execution of the algorithm. We present a number of algorithms for general networks, as well as upper and lower bounds for specific network topologies.
Traditionally many proofs in real time scheduling theory were informal and lacked the rigor usually required for good mathematical proofs. Some attempts have been made towards making the proofs more reliable, including using formal logics to specify scheduling algorithms and verify their properties. In particular, Duration Calculus, a real time interval temporal logic, has been used since timing requirements in scheduling can be naturally associated with intervals. This paper aims to improve the work in this area and give a summary. Static and dynamic priority scheduling algorithms are formalised in Duration Calculus and classical theorems for schedulability analysis are proven using the formal proof system of Duration Calculus.
This paper addresses the following general problem of tree regular model-checking: decide whether R * ( L ) ∩ L p = θ where R * is the reflexive and transitive closure of a successor relation induced by a term rewriting system R , and L and L p are both regular tree languages. We develop an automatic approximation-based technique to handle this - undecidable in general - problem in most practical cases, extending a recent work by Feuillade, Genet and Viet Triem Tong. We also make this approach fully automatic for practical validation of security protocols.
Modelling is applied increasingly more in software development; from developing sketches to blueprints of design and approaches that use models in all phases of software development such as the model-driven engineering approach. Consequently, developers need tools and techniques that allow them to reflect upon the quality of the models, as well as the environment used for developing these models such as modelling languages, modelling processes and tools. This article describes work on developing quality models in model-based software development by identifying stakeholders and their purposes of modelling, specifying quality goals based on these purposes, identifying means or practices required to achieve quality goals and selecting proper evaluation methods. These are steps in developing quality models that include rationale for selecting quality goals and is supported by a process, a metamodel and a tool developed in Eclipse. The contributions of the approach are firstly providing a framework for developing quality models that is tailored to model-based software development and secondly providing example quality models that may be reused by different projects, thus facilitating work on quality issues in software development.
Reflective command interfaces allow the changing of the command language by using the language itself. We argue that reflective command languages can be useful in many applications that allow the introduction of new types of concepts to be used in the application. We propose an approach to support reflective command languages through metamodeling, so that a reflective command interface can be automatically generated on the basis of a conceptual model of the application, given as an instance of a metamodel. A prototype implementation of the required infrastructure has been developed and used as a proof-of-concept, applied for a small example application.
