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  • 201.
    Castegren, Elias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Wrigstad, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Reference Capabilities for Concurrency Control2016In: ECOOP 2016 — Object-Oriented Programming, 2016Conference paper (Refereed)
    Abstract [en]

    The proliferation of shared mutable state in object-oriented programming complicates software development as two seemingly unrelated operations may interact via an alias and produce unexpected results. In concurrent programming this manifests itself as data-races.

    Concurrent object-oriented programming suffers from the fact that code that warrants synchronisation cannot easily be distinguished from code that does not. The burden is placed solely on the programmer to reason about alias freedom, sharing across threads and side-effects to deduce where and when to apply concurrency control, without inadvertently blocking parallelism.

    This paper presents a reference capability approach to concurrent and parallel object-oriented programming where all uses of aliases are guaranteed to be data-race free. Locations' static types describe their possible sharing. Type information can express non-interfering deterministic parallelism without dynamic concurrency control, thread-locality, lock-based schemes, and guarded-by relations giving multi-object atomicity to nested data structures. Unification of capabilities and traits allows trait-reuse across multiple concurrency scenarios with minimal code duplication. The resulting system brings together features from a wide range of prior work in a unified way.

  • 202.
    Castegren, Elias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Wrigstad, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Reference Capabilities for Trait Based Reuse and Concurrency Control2016Report (Other academic)
    Abstract [en]

    The proliferation of shared mutable state in object-orientedprogramming complicates software development as two seeminglyunrelated operations may interact via an alias and produceunexpected results. In concurrent programming this manifestsitself as data-races.

    Concurrent object-oriented programming further suffers from thefact that code that warrants synchronisation cannot easily bedistinguished from code that does not. The burden is placed solelyon the programmer to reason about alias freedom, sharing acrossthreads and side-effects to deduce where and when to applyconcurrency control, without inadvertently blocking parallelism.

    This paper presents a reference capability approach to concurrentand parallel object-oriented programming where all uses of aliasesare guaranteed to be data-race free. The static type of an aliasdescribes its possible sharing without using explicit ownership oreffect annotations. Type information can express non-interferingdeterministic parallelism without dynamic concurrency control,thread-locality, lock-based schemes, and guarded-by relationsgiving multi-object atomicity to nested data structures.Unification of capabilities and traits allows trait-based reuseacross multiple concurrency scenarios with minimal codeduplication. The resulting system brings together features from awide range of prior work in a unified way.

  • 203.
    Castegren, Elias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Wrigstad, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Relaxed Linear References for Lock-free Data Structures2017In: / [ed] Peter Müller, 2017, p. 47:1-47:31, article id 47Conference paper (Refereed)
    Abstract [en]

    Linear references are guaranteed to be free from aliases. This is a strong property that simplifies reasoning about programs and enables powerful optimisations, but it is also a property that is too strong for many applications. Notably, lock-free algorithms, which implement protocols that ensure safe, non-blocking concurrent access to data structures, are generally not typable with linear references because they rely on aliasing to achieve lock-freedom.

    This paper presents LOLCAT, a type system with a relaxed notion of linearity that allows an unbounded number of aliases to an object as long as at most one alias at a time owns the right to access the contents of the object. This ownership can be transferred between aliases, but can never be duplicated. LOLCAT types are powerful enough to type several lock-free data structures and give a compile-time guarantee of absence of data-races when accessing owned data. In particular, LOLCAT is able to assign types to the CAS (compare and swap) primitive that precisely describe how ownership is transferred across aliases, possibly across different threads. The paper introduces LOLCAT through a sound core procedural calculus, and shows how LOLCAT can be applied to three fundamental lock-free data structures. It also discusses a prototype implementation which integrates LOLCAT with an object-oriented programming language.

  • 204.
    Castegren, Elias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Wrigstad, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Types for CAS: Relaxed Linearity with Ownership Transfer2017In: Article in journal (Other academic)
    Abstract [en]

    Linear references are guaranteed to be free from aliases. This is a strong property that simplifies reasoning about programs and enables powerful optimisations, but it is also a property that is too strong for many applications. Notably, lock-free algorithms, which implement protocols that ensure safe, non-blocking concurrent access to data structures, are generally not typable with linear references because they rely on aliasing to achieve lock-freedom.

    This paper presents LOLCAT, a type system with a relaxed notion of linearity that allows an unbounded number of aliases to an object as long as at most one alias at a time owns the right to access the contents of the object. This ownership can be transferred between aliases, but can never be duplicated. LOLCAT types are powerful enough to type several lock-free data structures and give a compile-time guarantee of absence of data-races when accessing owned data. In particular, LOLCAT is able to assign types to the CAS (compare and swap) primitive that precisely describe how ownership is transferred across aliases, possibly across different threads.

    The paper introduces LOLCAT through a sound core procedural calculus, and shows how LOLCAT can be applied to three fundamental lock-free data structures. It also shows how LOLCAT can be used to implement synchronisation primitives like locks, and discusses a prototype implementation which integrates LOLCAT with an object-oriented programming language.

  • 205.
    Castegren, Elias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Wrigstad, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Types for CAS: Relaxed Linearity with Ownership Transfer2016Conference paper (Refereed)
    Abstract [en]

    This extended abstract overviews work on a type system for lock-free programming based on compare-and-swap. The type system prevents atomicity violations in lock-free programs, where insertion and removal of objects from a linked structure would be subject to data-races breaking linearity of ownership. The type system has successfully been applied to a small number of lock-free data structures.

  • 206.
    Castegren, Elias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Östlund, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Wrigstad, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Refined Ownership: Fine-grained controlled internal sharing2015In: Formal Methods for Multicore Programming, 2015, Vol. 9104, p. 179-210Conference paper (Refereed)
    Abstract [en]

    Ownership type systems give a strong notion of separation between aggregates. Objects belonging to different owners cannot be aliased, and thus a mutating operation internal to one object is guaranteed to be invisible to another. This naturally facilitates reasoning about correctness on a local scale, but also proves beneficial for coarse-grained parallelism as noninterference between statements touching different objects is easily established. For fine-grained parallelism, ownership types fall short as owner-based disjointness only allows separation of the innards of different aggregates, which is very coarse-grained. Concretely: ownership types can reason about the disjointness of two different data structures, but cannot reason about the internal structure or disjointness within the data structure, without resorting to static and overly constraining measures. For similar reasons, ownership fails to determine internal disjointness of external pointers to objects that share a common owner. In this paper, we introduce the novel notion of refined ownership which overcomes these limitations by allowing precise local reasoning about a group of objects even though they belong to the same external owner. Using refined ownership, we can statically check determinism of parallel operations on tree-shaped substructures of a data structure, including operations on values external to the structure, without imposing any non-local alias restrictions.

  • 207. Castellani, Ilaria
    et al.
    Victor, BjörnUppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    EXPRESS'99: 6th International Workshop on Expressiveness in Concurrency1999Conference proceedings (editor) (Other academic)
  • 208.
    Chen, Bolin
    et al.
    Univ Sheffield, Dept Elect & Elect Engn, Sheffield S38AN, S Yorkshire, England.
    You, Lei
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Yuan, Di
    Linkoping Univ, Dept Sci & Technol, S-60174 Norrkoping, Sweden.
    Pappas, Nikolaos
    Linkoping Univ, Dept Sci & Technol, S-60174 Norrkoping, Sweden.
    Zhang, Jie
    Univ Sheffield, Dept Elect & Elect Engn, Sheffield S38AN, S Yorkshire, England.
    Resource Optimization for Joint LWA and LTE-U in Load-Coupled and Multi-Cell Networks2019In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 23, no 2, p. 330-333Article in journal (Refereed)
    Abstract [en]

    We consider the performance optimization of multi-cell networks with LTE and Wi-Fi aggregation (LWA) and LTE-unlicensed (LTE-U) with sharing of the unlicensed band. Theoretical results are derived to enable an algorithm to approach the optimum. Numerical results show the algorithm's effectiveness and benefits of joint use of LWA and LTE-U.

  • 209.
    Chen, Xiaoqiang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Huang, Vincent
    Privacy preserving data publishing for recommender system2012In: Proc. 36th International Computer Software and Applications Conference Workshops, IEEE Computer Society, 2012, p. 128-133Conference paper (Refereed)
  • 210.
    Christakis, Maria
    et al.
    ETH Zurich.
    Gotovos, Alkis
    ETH Zurich.
    Sagonas, Konstantinos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Systematic testing for detecting concurrency errors in Erlang programs2013In: Proc. 6th International Conference on Software Testing, Verification and Validation, IEEE Computer Society, 2013, p. 154-163Conference paper (Refereed)
  • 211. Christakis, Maria
    et al.
    Sagonas, Konstantinos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Detection of asynchronous message passing errors using static analysis2011In: Practical Aspects of Declarative Languages, Springer Berlin/Heidelberg, 2011, p. 5-18Conference paper (Refereed)
  • 212. Christakis, Maria
    et al.
    Sagonas, Konstantinos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Static detection of race conditions in Erlang2010In: Practical Aspects of Declarative Languages: PADL 2010, Berlin: Springer-Verlag , 2010, p. 119-133Conference paper (Refereed)
  • 213.
    Claret, Guillaume
    et al.
    Microsoft Research.
    Rajamani, Sriram
    Microsoft Research.
    Nori, Aditya
    Microsoft Research.
    Gordon, Andrew D.
    Microsoft Research, Cambridge.
    Borgström, Johannes
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Bayesian Inference Using Data Flow Analysis2013In: ESEC/FSE '13: Proceedings of the 9th joint meeting of the European Software Engineering Conference and the ACM SIGSOFT Symposium on the Foundations of Software Engineering / [ed] Bertrand Meyer, Luciano Baresi, and Mira Mezini, New York, NY, USA: ACM Press, 2013, p. 92-102Conference paper (Refereed)
    Abstract [en]

    We present a new algorithm for Bayesian inference over probabilistic programs, based on data flow analysis techniques from the program analysis community. Unlike existing techniques for Bayesian inference on probabilistic programs, our data flow analysis algorithm is able to perform inference directly on probabilistic programs with loops. Even for loop-free programs, we show that data flow analysis offers better precision and better performance benefits over existing techniques. We also describe heuristics that are crucial for our inference to scale, and present an empirical evaluation of our algorithm over a range of benchmarks.

  • 214.
    Clarke, Dave
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Helvensteijn, Michiel
    Schaefer, Ina
    Abstract Delta Modelling2015In: Mathematical Structures in Computer Science, ISSN 0960-1295, E-ISSN 1469-8072, Vol. 25, no 3, p. 482-527Article in journal (Refereed)
  • 215.
    Clarke, Dave
    et al.
    KU Leuven.
    Noble, James
    Victoria University of Wellington.
    Wrigstad, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Beyond the Geneva Convention on the Treatment of Object Aliasing2013In: Aliasing in Object-Oriented Programming: Types, Analysis, and Verification / [ed] Dave Clarke, James Noble, Tobias Wrigstad, Springer Berlin/Heidelberg, 2013, p. 1-6Chapter in book (Other academic)
  • 216.
    Clarke, Dave
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Wrigstad, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Vats: A safe, reactive storage abstraction2016In: Theory and Practice of Formal Methods: Essays Dedicated to Frank de Boer on the Occasion of His 60th Birthday / [ed] Ábrahám, Erika; Bonsangue, Marcello; Broch Johnsen, Einar, Springer, 2016, p. 140-154Chapter in book (Refereed)
  • 217.
    Clarke, Dave
    et al.
    KU Leuven.
    Östlund, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Sergey, Ilya
    KU Leuven.
    Wrigstad, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Ownership Types: A Survey2013In: Aliasing in Object-Oriented Programming: Types, Analysis, and Verification / [ed] Dave Clarke, James Noble, Tobias Wrigstad, Springer Berlin/Heidelberg, 2013, p. 15-58Chapter in book (Refereed)
  • 218. Cleaveland, Rance
    et al.
    Parrow, Joachim
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Computer Systems. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Steffen, Bernhard
    The Concurrency Workbench: A Semantics Based Tool for the Verification of Concurrent Systems1993In: ACM Transactions on Programming Languages and Systems, ISSN 0164-0925, E-ISSN 1558-4593, Vol. 15, no 1, p. 36-72Article in journal (Refereed)
  • 219.
    Clebsch, Sylvan
    et al.
    Microsoft Research, UK.
    Franco, Juliana
    Imperial College London, UK.
    Drossopoulou, Sophia
    Imperial College London, UK.
    Yang, Albert Mingkun
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Wrigstad, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Vitek, Jan
    Northeastern University, USA.
    Orca: GC and Type System Co-design for Actor Languages2017In: Proceedings of the ACM on Programming Languages, ISSN 2475-1421, Vol. 1, no OOPSLA, p. 1-28, article id 72Article in journal (Refereed)
    Abstract [en]

    ORCA is a concurrent and parallel garbage collector for actor programs, which does not require any STW steps, or synchronization mechanisms, and that has been designed to support zero-copy message passing and sharing of mutable data. ORCA is part of a runtime for actor-based languages, which was co-designed with the Pony programming language, and in particular, with its data race free type system. By co-designing an actor language with its runtime, it was possible to exploit certain language properties in order to optimize performance of garbage collection. Namely, ORCA relies on the guarantees of absence of race conditions in order to avoid read/write barriers, and it leverages the actor message passing, for synchronization among actors.

    In this paper we briefly describe Pony and its type system. We use pseudo-code in order to introduce how ORCA allocates and deallocates objects, how it shares mutable data without requiring barriers upon data mutation, and how can immutability be used to further optimize garbage collection. Moreover, we discuss the advantages of co-designing an actor language with its runtime, and we demonstrate that ORCA can be implemented in a performant and scalable way through a set of micro-benchmarks, including a comparison with other well-known collectors.

  • 220. Cok, David R.
    et al.
    Stump, Aaron
    Weber, Tjark
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    The 2013 Evaluation of SMT-COMP and SMT-LIB2015In: Journal of automated reasoning, ISSN 0168-7433, E-ISSN 1573-0670, Vol. 55, no 1, p. 61-90Article in journal (Refereed)
    Abstract [en]

    After 8 years of SMT Competitions, the SMT Steering Committee decided, for 2013, to sponsor an evaluation of the status of SMT benchmarks and solvers, rather than another competition. This report summarizes the results of the evaluation, conducted by the authors. The key observations are that (1) the competition results are quite sensitive to randomness and (2) the most significant need for the future is assessment and improvement of benchmarks in the light of SMT applications. The evaluation also measured competitiveness of solvers, general coverage of solvers, logics, and benchmarks, and degree of repeatability of measurements and competitions.

  • 221. Cozza, Vittoria
    et al.
    Messina, Antonio
    Montesi, Danilo
    Arietta, Luca
    Magnani, Matteo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Spatio-Temporal Keyword Queries in Social Networks2013In: 17th East-European Conference on Advances in Databases and Information Systems (ADBIS), 2013, p. 70-83Conference paper (Refereed)
    Abstract [en]

    Due to the large amount of social network data produced at an ever growing speed and their complex nature, recent works have addressed the problem of efficiently querying such data according to social, temporal or spatial dimensions. In this work we propose a data model that keeps into account all these dimensions and we compare different approaches for efficient query execution on a large real dataset using standard relational technologies.

  • 222.
    Dalmau, V
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Computing Science.
    Pearson, J
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Computing Science. Docs.
    Closure functions and width 1 problems1999Conference paper (Refereed)
    Abstract [en]

    Local Consistency has proven to be an important notion in the study of constraint satisfaction problems. We give an algebraic condition that characterizes all the constraint types for which generalized are-consistency is sufficient to ensure the existence

  • 223.
    Daniels, Mats
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Cajander, Åsa
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis and Human-Computer Interaction.
    Eckerdal, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computational Science.
    Lind, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computerized Image Analysis and Human-Computer Interaction.
    Nylén, Aletta
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Clear, Tony
    McDermott, Roger
    Competencies for paradigm shift "survival"2015In: Proc. 45th ASEE/IEEE Frontiers in Education Conference, Piscataway, NJ: IEEE Press, 2015, p. 1424-1429Conference paper (Refereed)
  • 224.
    Daniels, Wilfried
    et al.
    Katholieke Univ Leuven, IMinds DistriNet, B-3001 Leuven, Belgium.
    Proença, José
    Katholieke Univ Leuven, IMinds DistriNet, B-3001 Leuven, Belgium; Univ Minho, HASLab INESC TEC, P-4719 Braga, Portugal.
    Clarke, Dave
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Joosen, Wouter
    Katholieke Univ Leuven, IMinds DistriNet, B-3001 Leuven, Belgium.
    Hughes, Danny
    Katholieke Univ Leuven, IMinds DistriNet, B-3001 Leuven, Belgium.
    Refraction: Low-cost management of reflective meta-data in pervasive component-based applications2015In: Proc. 18th International ACM SIGSOFT Symposium on Component-Based Software Engineering, New York: ACM Press, 2015, p. 27-36Conference paper (Refereed)
    Abstract [en]

    This paper proposes the concept of refraction, a principled means to lower the cost of managing reflective meta-data for pervasive systems. While prior work has demonstrated the bene fits of reflective component-based middleware for building open and reconfigurable applications, the cost of using remote reflective operations remains high. Refractive components address this problem by selectively augmenting application data flows with their reflective meta-data, which travels at low cost to reflective pools, which serve as loci of inspection and control for the distributed application. Additionally reflective policies are introduced, providing a mechanism to trigger reconfigurations based on incoming reflective meta-data. We evaluate the performance of refraction in a case-study of automatic con figuration repair for a real-world pervasive application. We show that refraction reduces network overhead in comparison to the direct use of reflective operations while not increasing development overhead. To enable further experimentation with the concept of refraction, we provide RxCom, an open-source refractive component model and supporting runtime environment.

  • 225. de Boer, Frank
    et al.
    Broch Johnsen, Einar
    Olso University.
    Clarke, Dave
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Drossopoulou, Sophia
    Imperial College London.
    Yoshida, Nobuko
    Imperial College London.
    Wrigstad, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Scaling Future Software: The Manycore Challenge2014Other (Other (popular science, discussion, etc.))
    Abstract [en]

    Existing software cannot benefit from the revolutionary potential increases in computational power provided by manycore chips unless their design and code are polluted by an unprecedented amount of low-level, fine-grained concurrency detail. As a consequence, the advent of manycore chips threatens to make current main-stream programming approaches obsolete, and thereby, jeopardizes the benefits gained from the last 20 years of development in industrial software engineering. In this article we put forward an argument for a fundamental breakthrough in how parallelism and concurrency are integrated into the software of the future.

  • 226. De Boer, Frank
    et al.
    Serbanescu, Vlad
    Hähnle, Reiner
    Henrio, Ludovic
    Rochas, Justine
    Din, Crystal Chang
    Johnsen, Einar Broch
    Sirjani, Marjan
    Khamespanah, Ehsan
    Fernández-Reyes, Kiko
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Yang, Albert Mingkun
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    A survey of active object languages2017In: ACM Computing Surveys, ISSN 0360-0300, E-ISSN 1557-7341, Vol. 50, no 5, article id 76Article in journal (Refereed)
    Abstract [en]

    To program parallel systems efficiently and easily, a wide range of programming models have been proposed, eachwith different choices concerning synchronization and communication between parallel entities. Among them, the actor model is based on loosely coupled parallel entities that communicate by means of asynchronous messages and mailboxes. Some actor languages provide a strong integration with object-oriented concepts; these are often called active object languages. This article reviews four major actor and active object languages and compares them according to carefully chosen dimensions that cover central aspects of the programming paradigms and their implementation.

  • 227. Dekker, Jip J.
    et al.
    Björdal, Gustav
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Carlsson, Mats
    Flener, Pierre
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Monette, Jean-Noël
    Auto-tabling for subproblem presolving in MiniZinc2017In: Constraints, ISSN 1383-7133, E-ISSN 1572-9354, Vol. 22, no 4, p. 512-529Article in journal (Refereed)
  • 228. Demoen, Bart
    et al.
    Sagonas, Konstantinos
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Computing Science. Datalogi.
    CAT: the Copying Approach to Tabling1999In: Journal of Functional and Logic Programming: Special Issue on Selected Best Papers from PLILP/ALP'98, Vol. 1999, no 2, p. 1-38Article in journal (Refereed)
  • 229. Demoen, Bart
    et al.
    Sagonas, Konstantinos
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Computing Science. Datalogi.
    Heap Memory Management in Prolog with Tabling: Practice and Experience2001In: Journal of Functional and Logic Programming: Special Issue on Selected Best Papers from PADL 2000, Vol. 9, p. 1-56Article in journal (Refereed)
  • 230.
    Deng, Tao
    et al.
    Southwest Jiaotong Univ, Inst Mobile Commun, Chengdu, Sichuan, Peoples R China..
    Ahani, Ghafour
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science. Komar Univ Sci & Technol, Dept Comp Engn, Sulaymaniyah, Iraq..
    Fan, Pingzhi
    Southwest Jiaotong Univ, Inst Mobile Commun, Chengdu, Sichuan, Peoples R China..
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Cost-Optimal Caching for D2D Networks with Presence of User Mobility2017In: GLOBECOM 2017 - 2017 IEEE Global Communications Conference, IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    Caching popular files at user equipments (UEs) provides an effective way to alleviate the burden of the back-haul networks. Generally, popularity based caching is not a system-wide optimal strategy, especially for mobility scenarios. Motivated by this observation, an optimal caching problem with respect to user mobility is investigated. To be specific, a cost-optimal caching problem (COCP) for device-to-device (D2D) networks is formulated, in which the impact of user mobility, cache size, and total number of encoded file segments are considered. Compared with the related studies, our investigation guarantees that the collected segments are non-overlapping, takes into account the cost of downloading from the network, and provides a rigorous complexity analysis. For problem solving, we first prove that the optimal caching placement of one user, giving other users' caching placements, can be derived in polynomial time. Then, based on this proof, a fast yet effective caching placement algorithm for all users is developed. Simulation results verify the effectiveness of this algorithm by comparing it to conventional caching algorithms.

  • 231. Deng, Tao
    et al.
    Ahani, Ghafour
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Fan, Pingzhi
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Cost-optimal caching for D2D networks with user mobility: Modeling, analysis, and computational approaches2018In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, no 5, p. 3082-3094Article in journal (Refereed)
  • 232.
    Deng, Tao
    et al.
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu 610031, Sichuan, Peoples R China.
    Fan, Pingzhi
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu 610031, Sichuan, Peoples R China.
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Optimizing Retention-Aware Caching in Vehicular Networks2019In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 67, no 9, p. 6139-6152Article in journal (Refereed)
    Abstract [en]

    Caching is an effective way to address the challenges due to explosive data traffic growth and massive device connectivity in fifth-generation (5G) networks. Currently, few works on caching pay attention to the impact of the time duration for which content is stored, called retention time, on caching optimization. The research on retention time is motivated by two practical issues, i.e., flash memory damage and storage rental cost in cloud networks, together giving rise to the storage cost. How to optimize caching contents taking the storage cost into consideration is a challenging problem, especially for the scenarios with cache-enabled mobile nodes. In this paper, a retention-aware caching problem (RACP) in vehicular networks is formulated, considering the impact of the storage cost. The problem's complexity analysis is provided. For symmetric cases, an optimal dynamic programming (DP) algorithm with polynomial time complexity is derived. For general cases, a low complexity and effective retention aware multi-helper caching algorithm (RAMA) is proposed. Numerical results are used to verify the effectiveness of the algorithms.

  • 233. Deng, Tao
    et al.
    You, Lei
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Fan, Pingzhi
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Device caching for network offloading: Delay minimization with presence of user mobility2018In: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345, Vol. 7, no 4, p. 558-561Article in journal (Refereed)
  • 234. Dickison, Mark E.
    et al.
    Magnani, Matteo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Rossi, Luca
    IT University, Copenhagen.
    Multilayer Social Networks2016Book (Other academic)
    Abstract [en]

    Multilayer networks, in particular multilayer social networks, where users belong to and interact on different networks at the same time, are an active research area in social network analysis, computer science, and physics. These networks have traditionally been studied within these separate research communities, leading to the development of several independent models and methods to deal with the same set of problems. This book unifies and consolidates existing practical and theoretical knowledge on multilayer networks including data collection and analysis, modeling, and mining of multilayer social network systems, the evolution of interconnected social networks, and dynamic processes such as information spreading. A single real dataset is used to illustrate the concepts presented throughout the book, demonstrating both the practical utility and the potential shortcomings of the various methods. Researchers from all areas of network analysis will learn new aspects and future directions of this emerging field.

  • 235. Dubois, Catherine
    et al.
    Grinchtein, Olga
    Pearson, Justin
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Carlsson, Mats
    RISE SICS, Stockholm, Sweden.
    Exploring properties of a telecommunication protocol with message delay using interactive theorem prover2018In: Software Engineering and Formal Methods, Springer, 2018, p. 239-253Conference paper (Refereed)
  • 236. Duda, Dick
    et al.
    Hart, Peter
    Reboh, Rene
    Reiter, John
    Risch, Tore
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Computing Science. Datalogi.
    SYNTEL: Using a Functional Language for Financial Risk Assessment1987In: IEEE Expert, Vol. 2, no 3Article in journal (Refereed)
    Abstract [en]

    This article describes Syntel, a knowledge representation language used in building large-scale expert systems for financial risk assessment. Syntel is an outgrowth of rule-based systems such as MYCIN and network-based systems such as Prospector. Unlike typical rule- or frame-based expert system shells, however, Syntel is a data-driven, purely functional language providing probabilistic inference plus many kinds of functionality associated with spreadsheets and database systems.

  • 237.
    Ecker, Grit
    et al.
    INFORM GmbH, Risk & Fraud Division, Aachen, Germany.
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science. Department of Science and Technology, Linköping University, Norrköping, Sweden.
    Koster, Arie M. C. A.
    Lehrstuhl II für Mathematik, RWTH Aachen University, Aachen, Germany.
    Schmeink, Anke
    Institute for Theoretical Information Technology, RWTH Aachen University, Aachen, Germany.
    Accurate optimization models for interference constrained bandwith allocation in cellular networks2019In: Computers & Operations Research, ISSN 0305-0548, E-ISSN 1873-765X, Vol. 101, p. 1-12Article in journal (Refereed)
    Abstract [en]

    In cellular networks, the signal-to-interference-plus-noise ratio (SINR) is a key metric for link availability and quality. For network planning purposes, a straightforward modeling unfortunately yields numerically difficult optimization models. Further, given a required data rate of a link, its bandwidth consumption depends nonlinearly on the SINR.

    In this paper, we develop two novel approaches to jointly model SINR-based link availability and bandwidth requirements accurately. The first approach is a set-wise formulation from a user’s point of view, while the second one exploits discrete channel quality indicators. We compare these formulations with three known approximate approaches numerically, revealing the clear outperformance of our approaches in terms of exactness. Moreover, since the exact models comprise an exponential number of either variables or constraints, we discuss their pros and cons in a further computational study and develop a more efficient algorithm dealing implicitly with the involved constraints.

  • 238.
    Eckerdal, Anna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Scientific Computing. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computational Science.
    Kinnunen, Päivi
    Thota, Neena
    Nylén, Aletta
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Sheard, Judy
    Malmi, Lauri
    Teaching and learning with MOOCs: Computing academics' perspectives and engagement2014In: Proc. 19th Conference on Innovation and Technology in Computer Science Education, New York: ACM Press , 2014, p. 9-14Conference paper (Refereed)
  • 239. Elin, Dan
    et al.
    Risch, Tore
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Faculty of Science and Technology, Biology, Department of Ecology and Evolution, Computing Science. Datalogi.
    Amos II Java Interfaces2000Report (Other scientific)
  • 240.
    Elsts, Atis
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Optimal Task Allocation in Sensor and Actuator Networks2015In: Proc. 11th Swedish National Computer Networking Workshop, 2015Conference paper (Refereed)
    Abstract [en]

    Sensor and actuator network macroprogramming techniques that use task graphs are promising options for high-level application development in this domain. However, setting up a multitude of application-level tasks in the network and subsequently keeping track of them is a nontrivial undertaking. Therefore, tool support for automated task allocation is required. Such a support is typically implemented by providing an objective function that evaluates the cost of a task mapping, and a search algorithm that attempts to minimize this function.The current algorithms for task allocation in sensor and actuator networks either do not guarantee optimal results, or are conceptually tied to a single specific objective function. Our work contributes to this state-of-art in two aspects: firstly, by finding a model that can easily accommodate several different objective functions, and secondly, by finding a search strategy that makes it feasible to allocate realistic task graphs even in large networks.

  • 241.
    Elsts, Atis
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Hassani Bijarbooneh, Farshid
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Jacobsson, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Sagonas, Konstantinos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Enabling design of performance-controlled sensor network applications through task allocation and reallocation2015In: Proc. 11th International Conference on Distributed Computing in Sensor Systems, IEEE Computer Society, 2015, p. 248-253Conference paper (Refereed)
    Abstract [en]

    Task Graph (ATaG) is a sensor network application development paradigm where the application is visually described by a graph where the nodes correspond to application-level tasks and edges correspond to dataflows. We extend ATaG with the option to add nonfunctional requirements: constraints on end-to-end delay and packet delivery rate. Setting up these constraints at the design phase naturally leads to enabling run-time assurance at the deployment phase, when the conditions of the constraints are used as network's performance goals. We provide both run-time middleware that checks the conditions of these constraints and a central management unit that dynamically adapts the system by doing task reallocation and putting task copies on redundant nodes. Through extensive simulations we show that the system is efficient enough to enable adaptations within tens of seconds even in large networks.

  • 242.
    Elsts, Atis
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Hassani Bijarbooneh, Farshid
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Jacobsson, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Sagonas, Konstantinos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    ProFuN TG: A tool for programming and managing performance-aware sensor network applications2015In: IEEE 40th Local Computer Networks Conference Workshops (LCN Workshops), IEEE Computer Society, 2015, p. 751-759Conference paper (Refereed)
    Abstract [en]

    Sensor network macroprogramming methodologiessuch as the Abstract Task Graph hold the promise of enablinghigh-level sensor network application development. However,progress in this area is hampered by the scarcity of tools, andalso because of insufficient focus on developing tool support forprogramming applications aware of performance requirements.

    We present ProFuN TG (Task Graph), a tool for designing sen-sor network applications using task graphs. ProFuN TG providesautomated task mapping, sensor node firmware macrocompila-tion, application simulation, deployment, and runtime mainte-nance capabilities. It allows users to incorporate performancerequirements in the applications, expressed through constraintson task-to-task dataflows. The tool includes middleware that usesan efficient flooding-based protocol to set up tasks in the network,and also enables runtime assurance by keeping track of theconstraint conditions.

    We show that the adaptive task reallocation enabled by ourapproach can significantly increase application reliability whiledecreasing energy consumption: in a network with unreliablelinks, we achieve above 99.89 % task-to-task PDR while keepingthe maximal radio duty cycle around 2.0 %.

  • 243.
    Elsts, Atis
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Hassani Bijarbooneh, Farshid
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Jacobsson, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Sagonas, Konstantinos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    ProFuN TG: A Tool Using Abstract Task Graphs to Facilitate the Development, Deployment and Maintenance of Wireless Sensor Network Applications2015In: Proc. Poster/Demo Session: 12th European Conference on Wireless Sensor Networks, 2015, p. 19-20Conference paper (Refereed)
    Abstract [en]

    In this demo abstract we present ProFuN TG (Task Graph), a tool for sensor network application development using the data-flow programming paradigm. The tool has support for the whole lifecycle of WSN application: from the initial design of its task graph, task placement on network nodes, execution in a simulated environment, deployment on real hardware, to its automated maintenance through task remapping. ProFuN TG allows to program applications that incorporate quality-of-service requirements, expressed through constraints on task-to-task data flows.

  • 244.
    Elsts, Atis
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Hassani Bijarbooneh, Farshid
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Jacobsson, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Sagonas, Konstantinos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    ProFuN TG: Programming Sensornets with Task Graphs for Increased Reliability and Energy-Efficiency2015Conference paper (Refereed)
    Abstract [en]

    Sensor network macroprogramming methodologies such as the Abstract Task Graph hold the promise of enabling high-level sensor network application development. However, progress in this area is hampered by the scarcity of tools, and also because of insufficient focus on developing tool support for programming applications aware of performance requirements.

    In this demo we present ProFuN TG (Task Graph), a tool for designing sensor network applications using task graphs. ProFuN TG provides automated task mapping, sensor nodefirmware macrocompilation, application simulation, deployment, and runtime maintenance capabilities. It allows users to incorporate performance requirements in the applications, expressed through constraints on task-to-task dataflows. The tool includes middleware that uses an efficient flooding-based protocol to set up tasks in the network, and also enables runtime assurance by keeping track of the constraint conditions.

    Through task allocation in a way that optimizes an objective function in a model of the network, and adaptive task reallocation in case of link, node, or sensor failures the tool helps to make sensornet applications both more energy-efficient and reliable.

  • 245.
    Elsts, Atis
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Ngai, Edith C.-H.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    A Case for Node-Local Runtime Parameter Adaptation in Wireless Sensor Networks2014In: Proc. 10th Swedish National Computer Networking Workshop, 2014Conference paper (Other academic)
    Abstract [en]

    The challenges posed to wireless sensor networks by the environments they are deployed cannot always be predicted beforehand. Therefore, adaptive behavior at the run-time may be required to achieve good reliability and energy-efficiency. We present a node-local runtime adaptation algorithm that adapts the over-the-air message encoding based on presence of weak links and external interference in the immediate neighborhood of the node. Evaluation with a network simulator shows that this algorithm leads to significant network-wide reduction of radio duty cycle under specific radio transmission failure models.

  • 246.
    Eriksson, Lars-Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    The GTO Toolset and Method2007In: Electronical Notes in Theoretical Computer Science, ISSN 1571-0661, E-ISSN 1571-0661, Vol. 185, p. 77-91Article in journal (Refereed)
    Abstract [en]

    A suitable method supported by a toolset with a high degree of automation is a necessity for the successful employment of formal methods in industrial projects.

    The GTO toolset and method have been developed, and successfully applied, to formal methods in safety-critical control applications related to railway signalling since the mid 1990s. The toolset and method support the entire formal methods process from writing and validating formal specifications, through modelling of the implementation to formal verification and analysis of verification results. One goal the toolset and method was to make formal methods more competitive by streamlining the process so that -- at least within an established application area -- individual verification tasks could be done in an "assembly line"-like fashion with minimum overhead.

    In line with this goal, the toolset is intended for use with configurable systems, where a generic specification is applicable to a family of systems and adapted to a specific system using configuration data.

    The functions carried out by the toolset include static checking and simulation of specifications, checking of configuration data, generation of implementation models from PLC program code or relay schematics, simulation of the implementation model, formal verification by refinement proof, and analysis of failed refinement proofs. Refinement proofs are automatically carried out by a satisfiability (SAT) solver of the user's choice, which is interfaced to the main tool.

    We will outline the method and functions of the toolset as well as the formal notation -- a simple temporal predicate logic -- used by the toolset.

  • 247.
    Eriksson, Lars-Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science. Datalogi.
    Use of Domain Theories in Applied Formal Methods2006Report (Other academic)
    Abstract [en]

    A formal theory of an application domain can serve a key role in formal specification and verification of systems operating in that domain. This is particularly relevant when working with families of similar systems intended to control some kind of industrial process or function where the control principles are general while the specifics of the system depend on the particular installation the system is intended to control. In such situations a domain theory can facilitate writing generic specifications or implementations for the entire family of systems which can then be configured for each particular installation. Use of concepts defined in the domain theory can also facilitate communication with domain experts without knowledge in formal methods.

    An example of such a family is railway signalling systems which all implement the same general signalling principles of ensuring safe train operation, while the exact function of a particular signalling system depends on the railway track layout under its control.

    We will give concrete examples from industrial practise in the railway domain, showing how domain theories can help in the formal verification process. The examples include writing and validating formal specifications, formally verifying implementations and analysing and communicating the results of failed verifications.

  • 248.
    Eriksson, Lars-Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science. Datalogi.
    Using Formal Methods in a Retrospective Safety Case2004In: Computer Safety, Reliability, and Security: 23rd International Conference, SAFECOMP 2004, Potsdam, Germany, September 21-24, 2004. Proceedings, 2004Conference paper (Refereed)
    Abstract [en]

    Today the development of safety-critical systems is to a large extent guided by standards that make demands on both development process and system quality. Before the advent of these standards, development was typically done on a "best practise'' basis which could differ much between application areas. Some safety-critical systems (e.g. railway interlockings) have a long technical and economical lifetime so that today we have many legacy safety-critical systems in operation which were developed according to practises that would be regarded as unacceptable today. Usually, such systems are allowed to continue operating by virtue of past performance. If there is doubt about the integrity of a legacy system, an alternative to replacement could be making a "retrospective'' safety case demonstrating that the legacy system is indeed safe to use. Using as example a case taken from railway signalling, we will show how formal verification can be used in a retrospective safety case. In this application of formal methods several particular problems arise, such as uncertainty about the original requirements and the required safety level of the various system functions. We will discuss such problems and the approach taken to deal with them in the example case.

  • 249.
    Eriksson, Lars-Henrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science. Datalogi.
    Lindsay, Peter
    FME 2002: Formal Methods -- Getting IT Right2002Conference proceedings (editor) (Refereed)
  • 250.
    Eriksson, Lars-Henrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Lindsay, Peter Alexander
    FME 2002: Formal Methods - Getting IT Right : International Symposium of Formal Methods Europe, Copenhagen, Denmark, July 22-24, 2002. Proceedings2002Conference proceedings (editor) (Refereed)
2345678 201 - 250 of 838
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