Fundamenta Informaticae - Volume 112, issue 4

Authors: Dinu, Anca

Article Type: Research Article

Abstract: We show in this paper how the computer science concept of ‘continuations’, together with categorial grammars and a type shifting mechanism, is able to account for a wide range of natural language semantic phenomena, such as hierarchical discourse structure, ellipses, accommodation and free-focus and bound-focus anaphora. The merit of continuations in the dynamic semantics framework is that they abstract away from assignment functions that are essential to the formulations of Dynamic Intensional Logic, Dynamic Montague Grammar, Dynamic Predicate Logic and Discourse Representation Theory, Thus, continuation style semantic do not pose problems such as the destructive assignment problem in Dynamic Predicate …Logic or the variable clash problem in Discourse Representation Theory. We argue that continuations are a versatile and powerful tool, particularly well suited to manipulate scope and long distance dependencies, phenomena that abound in natural language semantics. Show more

Keywords: ’continuations’, dynamic semantics, lambda calculus, type shifting, scope, anaphora

DOI: 10.3233/FI-2011-590

Citation: Fundamenta Informaticae, vol. 112, no. 4, pp. 263-280, 2011

Authors: Martin, Gabriela | Steinby, Magnus

Article Type: Research Article

Abstract: We study approximations of regular languages bymembers of a given variety ℒ of regular languages. These are upper or lower approximations in the sense of Pawlak's rough set theory with respect to congruences belonging to the variety of congruences corresponding to ℒ. In particular, we consider the closest upper and lower approximations in ℒ. In so-called principal varieties these always exist, and we present algorithms for finding them, but for other varieties the situation is more complex. Although we consider just Eilenberg’s +-varieties, the general ideas apply also to other types of varieties of languages. Our work may also be …viewed as an approach to the characterizable inference problem in which a language of a certain kind is to be inferred from a given sample. Show more

Keywords: Regular languages, rough approximations, varieties of languages, finite automata

DOI: 10.3233/FI-2011-591

Citation: Fundamenta Informaticae, vol. 112, no. 4, pp. 281-303, 2011

Authors: Sabri, Khair Eddin | Khedri, Ridha

Article Type: Research Article

Abstract: Several organizations generate and store a wide range of information in what is commonly referred to as data stores. To access the information within these data stores, two main architectures are widely adopted. The first architecture gives access to information through a trusted server that enforces established confidentiality policies. The second one allows the information to be public but in its encrypted form. Then through a scheme for the distribution of cryptographic keys, each user is provided with the keys needed to decrypt only the part of the information she is authorized to access. This paper relates to the latter …architecture. We introduce an algebraic framework that takes into consideration a new perspective in tackling the key-distribution problem. We use the proposed framework to analyze key-distribution schemes that are representative of the ones found in the literature. The framework enables the specification and the verification of key-distribution policies. We also point to several other applications related to measures ensuring information confidentiality. Show more

Keywords: algebraic framework, cryptography, key distribution, information confidentiality

DOI: 10.3233/FI-2011-592

Citation: Fundamenta Informaticae, vol. 112, no. 4, pp. 305-335, 2011

Authors: Santana, Fabiana T. | Santana, Fágner L. | Guerreiro, Ana Maria G. | , Adrião D. | Dória Neto, | Santiago, Regivan H. N.

Article Type: Research Article

Abstract: In this article, we use the interval mathematics and targeted rounding by specific functions to establish a framework for interval quantization. The function approximation FId , that maps x to an interval [x1 , x2 ] such that x1 is the largest floating point number less than or equal to x and x2 is the smallest floating point number greater than or equal to x, is used to establish the sampling interval and the levels of interval quantization. We show that the interval quantization levels (Nj ) represent the specific quantization levels (nj ), that are comparable, according …to Kulisch- Miranker order and are disjoint two by two. If an interval signal X[n] intercepts a quantization interval level Nj , then the quantized signal will be Xq [n] = Nj . Moreover, for the interval quantization error (E[n] = Xq [n] − X[n]) an estimate is shown due to the quantization step and the number of levels. It is also presented the definition of interval coding, in which the number of required bits depends on the amount of quantization levels. Finally, in an example can be seen that the the interval quantization level represent the classical quantization levels and the interval error represents the classical quantization error. Show more

Keywords: Interval mathematics, interval representation, interval sampling, interval quantization, interval coding

DOI: 10.3233/FI-2011-593

Citation: Fundamenta Informaticae, vol. 112, no. 4, pp. 337-363, 2011

Authors: Shim, Kyung-Ah | Lee, Young-Ran

Article Type: Research Article

Abstract: Recently, Xiong et al. and Selvi et al. proposed a certificateless signature scheme secure in the standard model and a certificateless multi-receiver signcryption scheme secure in the random oracle model, respectively. In this paper, we show that they are insecure against malicious-butpassive KGC attacks. More specifically, the former does not achieve unforgeability and the latter does not satisfy confidentiality against type II adversaries.

Keywords: Certificateless signature, certificateless signcryption, certificatelessmulti-receiver signcryption, malicious-but-passive KGC attack, confidentiality, unforgeability

DOI: 10.3233/FI-2011-594

Citation: Fundamenta Informaticae, vol. 112, no. 4, pp. 365-376, 2011

Article Type: Other

Citation: Fundamenta Informaticae, vol. 112, no. 4, pp. 377-378, 2011