Journal of Computer and System Sciences (J Comput Syst Sci )


The Journal of Computer and System Sciences publishes original research papers in computer science and related subjects in system science, with attention to the relevant mathematical theory. Applications-oriented papers may also be accepted. Research Areas Include: Traditional Subjects such as: Theory of algorithms and computability; Formal languages; Automata theory; Contemporary Subjects such as Complexity theory Algorithmic; Complexity; Parallel and distributed computing; Computer networks; Neural networks; Computational learning theory; Database theory and practice Computer modeling of complex systems.

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  • Website
    Journal of Computer and System Sciences website
  • Other titles
    Journal of computer and system sciences (Online), Journal of computer and system sciences
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    Document, Periodical, Internet resource
  • Document type
    Internet Resource, Computer File, Journal / Magazine / Newspaper

Publications in this journal

  • [Show abstract] [Hide abstract]
    ABSTRACT: We define extensions of the full branching-time temporal logic CTL⁎ in which the path quantifiers are relativised by formal languages of infinite words, and consider its natural fragments obtained by extending the logics CTL and CTL+ in the same way. This yields a small and two-dimensional hierarchy of temporal logics parametrised by the class of languages used for the path restriction on one hand, and the use of temporal operators on the other. We motivate the study of such logics through two application scenarios: in abstraction and refinement they offer more precise means for the exclusion of spurious traces; and they may be useful in software synthesis where decidable logics without the finite model property are required. We study the relative expressive power of these logics as well as the complexities of their satisfiability and model-checking problems.
    Journal of Computer and System Sciences 01/2014; 80(2):375–389.
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    ABSTRACT: Recently proposed formal reliability analysis techniques have overcome the inaccuracies of traditional simulation based techniques but can only handle problems involving discrete random variables. In this paper, we extend the capabilities of existing theorem proving based reliability analysis by formalizing several important statistical properties of continuous random variables like the second moment and the variance. We also formalize commonly used concepts about the reliability theory such as survival, hazard, cumulative hazard and fractile functions. With these extensions, it is now possible to formally reason about important measures of reliability (the probabilities of failure, the failure risks and the mean-time-to failure) associated with the life of a system that operates in an uncertain and harsh environment and is usually continuous in nature. We illustrate the modeling and verification process with the help of examples involving the reliability analysis of essential electronic and electrical system components.
    Journal of Computer and System Sciences 01/2014; 80(2):323–345.
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    ABSTRACT: Recently proposed formal reliability analysis techniques have overcome the inaccuracies of traditional simulation based techniques but can only handle problems involving discrete random variables. In this paper, we extend the capabilities of existing ...
    Journal of Computer and System Sciences 01/2014; 80(2):321–322.
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    ABSTRACT: The displacement calculus of Morrill, Valentín and Fadda (2011) [25] aspires to replace the calculus of Lambek (1958) [13] as the foundation of categorial grammar by accommodating intercalation as well as concatenation while remaining free of structural rules and enjoying Cut-elimination and its good corollaries. Jäger (2005) [11] proposes a type logical treatment of anaphora with syntactic duplication using limited contraction. Morrill and Valentín (2010) [24] apply (modal) displacement calculus to anaphora with lexical duplication and propose extension with a negation as failure in conjunction with additives to capture binding conditions. In this paper we present an account of anaphora developing characteristics and employing machinery from both of these proposals.
    Journal of Computer and System Sciences 01/2014; 80(2):390–409.
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    ABSTRACT: This paper proposes an efficient broadcast encryption scheme for key distribution in MANET. No message exchange is required to establish a group key. The communication overhead remains unchanged as group size grows. In order for the group member to obtain session key, only one bilinear pairing computation is required. The proposal is also evaluated through efficiency, security analysis and comparison with other existing schemes. We test the efficiency of the scheme on a modern station through simulation. The performance analysis shows its suitability for large scale MANETs. It is shown that the new scheme is provable secure in standard model. The comparison indicates that this scheme has efficiency surpassing congeneric schemes. Furthermore, an improved scheme against chosen ciphertext attack (CCA) is proposed in order to enhance the security. Thus, the proposal in this paper can not only meet security demands but is also efficient in terms of computation and communication.
    Journal of Computer and System Sciences 01/2014; 80(3):533–545.
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    ABSTRACT: An investigation is carried out on the nature of QoS measures for queues with correlated traffic in both discrete and continuous time domains. The study focuses on the single server GIG/M[X]/1/N and GIG/Geo[X]/1/N queues with finite capacity, N, a general batch renewal arrival process (BRAP), GIG and either batch Poisson, M[X] or batch geometric, Geo[X] service times with general batch sizes, X. Closed form expressions for QoS measures, such as queue length & waiting time distributions and blocking probabilities are stochastically derived and showed to be, essentially, time domain invariant. Moreover, the sGGeosGGeo/Geo/1/N queue with a shifted generalised geometric (sGGeo) distribution is employed to assess the adverse impact of varying degrees of traffic correlations upon basic QoS measures and consequently, illustrative numerical results are presented. Finally, the global balance queue length distribution of the MGeo/MGeo/1/N queue is devised and reinterpreted in terms of information theoretic principle of entropy maximisation.
    Journal of Computer and System Sciences 01/2014;
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    ABSTRACT: We describe the mechanisation of some foundational results in the theory of context-free languages (CFLs), using the HOL4 system. We focus on pushdown automata (PDAs). We show that two standard acceptance criteria for PDAs (“accept-by-empty-stack” and “accept-by-final-state”) are equivalent in power. We are then able to show that the pushdown automata (PDAs) and context-free grammars (CFGs) accept the same languages by showing that each can emulate the other. With both of these models to hand, we can then show a number of basic, but important results. For example, we prove the basic closure properties of the context-free languages such as union and concatenation. Along the way, we also discuss the varying extent to which textbook proofs (we follow Hopcroft and Ullman) and our mechanisations diverge: sometimes elegant textbook proofs remain elegant in HOL; sometimes the required mechanisation effort blows up unconscionably.
    Journal of Computer and System Sciences 01/2014; 80(2):346–362.
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    ABSTRACT: Discovering frequent factors from long strings is an important problem in many applications, such as biosequence mining. In classical approaches, the algorithms process a vast database of small strings. However, in this paper we analyze a small database of long strings. The main difference resides in the high number of patterns to analyze. To tackle the problem, we have developed a new algorithm for discovering frequent factors in long strings. We present an Apriori-like solution which exploits the fact that any super-pattern of a non-frequent pattern cannot be frequent. The SANSPOS algorithm does a multiple-pass, candidate generation and test approach. Multiple length patterns can be generated in a pass. This algorithm uses a new data structure to arrange nodes in a trie. A Positioning Matrix is defined as a new positioning strategy. By using Positioning Matrices, we can apply advanced prune heuristics in a trie with a minimal computational cost. The Positioning Matrices let us process strings including Short Tandem Repeats and calculate different interestingness measures efficiently. Furthermore, in our algorithm we apply parallelism to transverse different sections of the input strings concurrently, speeding up the resulting running time. The algorithm has been successfully used in natural language and biological sequence contexts.
    Journal of Computer and System Sciences 01/2014; 80(1):3–15.
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    ABSTRACT: The aim of this paper is to introduce the dual notion of interval conjugate implications, the interval coimplications, as interval representations of corresponding conjugate fuzzy coimplications. Using the canonical representation, this paper considers both the correctness and the optimality criteria, in order to provide interpretation for fuzzy coimplications as the non-truth degree of conditional rule in expert systems and study the action of interval automorphisms on such interval fuzzy connectives. It is proved that interval automorphisms acting on NN-dual interval coimplications preserve the main properties of interval implications discussed in the literature including the duality principle. Lastly, the action of interval automorphisms on interval classes of border, model and S-coimplications are considered, summarized in commutative diagrams.
    Journal of Computer and System Sciences 01/2014; 80(2):410–425.
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    ABSTRACT: In self-hosted environments it was feared that Business Intelligence (BI) will eventually face a resource crunch situation due to the never ending expansion of data warehouses and the online analytical processing (OLAP) demands on the underlying networking. Cloud computing has instigated a new hope for future prospects of BI. However, how will BI be implemented on Cloud and how will the traffic and demand profile look like? This research attempts to answer these key questions in regards to taking BI to the Cloud. The Cloud hosting of BI has been demonstrated with the help of a simulation on OPNET comprising a Cloud model with multiple OLAP application servers applying parallel query loads on an array of servers hosting relational databases. The simulation results reflected that extensible parallel processing of database servers on the Cloud can efficiently process OLAP application demands on Cloud computing.
    Journal of Computer and System Sciences 01/2014;
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    ABSTRACT: The Pattern self-Assembly Tile set Synthesis (PATS) problem, which arises in the theory of structured DNA self-assembly, is to determine a set of coloured tiles that, starting from a bordering seed structure, self-assembles to a given rectangular colour pattern. The task of finding minimum-size tile sets is known to be NP-hard. We explore several complete and incomplete search techniques for finding minimal, or at least small, tile sets and also assess the reliability of the solutions obtained according to the kinetic Tile Assembly Model.
    Journal of Computer and System Sciences 01/2014; 80(1):297–319.
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    ABSTRACT: To secure multimedia communications, existing encryption techniques usually encrypt the whole data stream using the same session key during a session. The use of the session key confronts with tradeoff problem between session key creation latency and security for the real-time multimedia stream. The main feature of our proposed scheme is to selectively encrypt RTP packets using different one-time packet keys in the same session for real-time multimedia applications. The packet key, which has already been used, will never be reused throughout the same session. The use of the one-time packet key enables to improve security strength of real-time multimedia. To solve the issue of the real-time packet key exchanges related to the timely use of the one-time packet keys, this paper suggests the one-time packet key exchange method that does not need to occur on a packet-by-packet basis.
    Journal of Computer and System Sciences 01/2014;
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    ABSTRACT: Cloud systems provide significant benefits by allowing users to store massive amount of data on demand in a cost-effective manner. Role-based access control (RBAC) is a well-known access control model which can be used to protect the security of cloud data storage. Although cryptographic RBAC schemes have been developed recently to secure data outsourcing, these schemes assume the existence of a trusted administrator managing all the users and roles, which is not realistic in large-scale systems. In this paper, we introduce a cryptographic administrative model AdC-RBAC for managing and enforcing access policies for cryptographic RBAC schemes. The AdC-RBAC model uses cryptographic techniques to ensure that the administrative tasks are performed only by authorised administrative roles. Then we propose a role-based encryption (RBE) scheme and show how the AdC-RBAC model decentralises the administrative tasks in the RBE scheme thereby making it practical for security policy management in large-scale cloud systems.
    Journal of Computer and System Sciences 01/2014;
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    ABSTRACT: Cooperation is significantly influenced by participants' awareness of relevant information. The objective of this paper is to propose a methodology to design and develop applications that assist individuals to identify their awareness. Through extending Cooperative management Methodology for Enterprise Networks (CoMEN), this article introduces Policy-based Awareness Management (PAM) - a software engineering methodology that proposes the use of existing policy rules as a source to identify awareness. The methodology has been built on the logic of general awareness, and implements Directory Enabled Networks (DEN) policy structure. The contribution of the paper is illustrated through the wireless communication system at a hospital in Norway. We conclude that theory of General Awareness and in particular PAM as an extension of CoMEN, is effective to identify relevant information for agents.
    Journal of Computer and System Sciences 01/2014;

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