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Automated verification of pointer programs in
pointer logic
WANG Zhifang, CHEN Yiyun, WANG Zhenming, HUA Baojian
Front. Comput. Sci.. 2008, 2 (4): 380-397.
https://doi.org/10.1007/s11704-008-0033-8
Reasoning about pointer programs is difficult and challenging, while their safety is critical in software engineering. Storeless semantics pioneered by Jonkers provides a method to reason about pointer programs. However, the representation of memory states in Jonkers’ model is costly and redundant. This paper presents a new framework under a more efficient storeless model for automatically verifying properties of pointer programs related to the correct use of dynamically allocated memory such as absence of null dereferences, absence of dangling dereferences, absence of memory leaks, and preservation of structural invariants. The introduced logic – Pointer Logic, is developed to achieve such goals. To demonstrate that Pointer Logic is a useful storeless approach to verification, the Schorr-Waite tree-traversal algorithm which is always considered as a key test for pointer formalizations was verified via our analysis. Moreover, an experimental tool – plcc was implemented to automatically verify a number of non-trivial pointer programs.
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A Petri net-based approach for supporting aspect-oriented
modeling
GUAN Lianwei, LI Xingyu, HU Hao, LU Jian
Front. Comput. Sci.. 2008, 2 (4): 413-423.
https://doi.org/10.1007/s11704-008-0041-8
The concept of aspect-orientation allows for modularizing crosscutting concerns as aspect modules. Aspect-orientation originally emerged at the programming level, and has stretched over other development phases now. Among them aspect-oriented modeling (AOM) is a hot topic, and there are many approaches supporting it. Petri net is a good formalism which can provide the foundations for modeling software and simulating its execution, but fails to resolve the problem of crosscutting concerns to support AOM. So, this paper presents an approach which extends the Petri net so as to support the AOM. In this paper, the basic functions of the system are modeled as base net by Petri net, and the crosscutting concerns are modeled as aspect nets. In order to analyze the whole system, woven mechanism is proposed to compose the aspect nets and base net together. The problems about aspect-aspect conflict and conflict relations may exist among the aspect nets matching the shared join point, thus this paper propose solutions to resolve them. The Object Petri net which is an extension of traditional Petri net is also extended so as to support aspect-oriented modeling here.
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Style transformation in natural languages
HU Yue, GAO Xiaoyu, LI Li, GAO Qingshi
Front. Comput. Sci.. 2008, 2 (4): 424-430.
https://doi.org/10.1007/s11704-008-0037-4
To express semantic knowledge of natural languages accurately and unify the processing of languages, the style transformation of natural languages is discussed in an all-round way. The discussion covers purpose, voice, modal, tense, narrow sense of style, number and case. All style transformations may be described accurately by a four-element Descriptive Language of Style Transformation (STDL). The transformation between representation of semantic units without style and with style can be converted through style transformation function. Each style transformation function is a difference function in multiple natural languages. Such difference functions can be used to simplify language processing procedure and improve processing quality.
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An improved algorithm for gray image representation
using non-symmetry and anti-packing model with triangles and rectangles
ZHENG Yunping, CHEN Chuanbo, SAREM Mudar
Front. Comput. Sci.. 2008, 2 (4): 431-437.
https://doi.org/10.1007/S11704-008-0036-5
Although the triangle non-symmetry and anti-packing model (TNAM) representation for gray images is an effective image representation method, there is still much space left for optimization. In this paper, inspired by the optimization idea of the packing problem, we proposed an improved algorithm for gray image representation using the non-symmetry and anti-packing model with triangles and rectangles (NAMTR). By comparing the representation algorithm of the NAMTR with those of the TNAM and the popular linear quadtree, theoretical and experimental results presented in this paper show that the former can greatly reduce the number of sub-patterns or nodes and simultaneously save the data storage much more effectively than the latter, and therefore it is a better method to represent gray images. Representation method of the NAMTR, as envisaged in this paper, shows a very strong promise, and it is valuable for further theoretical research and potential business foreground, such as reducing storage space, increasing transmission speed and improving pattern match efficiency.
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A robust localization algorithm in wireless sensor
networks
LI Xin, HUA Bei, XIONG Yan, SHANG Yi
Front. Comput. Sci.. 2008, 2 (4): 438-450.
https://doi.org/10.1007/s11704-008-0018-7
Most of the state-of-the-art localization algorithms in wireless sensor networks (WSNs) are vulnerable to various kinds of location attacks, whereas secure localization schemes proposed so far are too complex to apply to power constrained WSNs. This paper provides a distributed robust localization algorithm called Bilateration that employs a unified way to deal with all kinds of location attacks as well as other kinds of information distortion caused by node malfunction or abnormal environmental noise. Bilateration directly calculates two candidate positions for every two heard anchors, and then uses the average of a maximum set of close-by candidate positions as the location estimation. The basic idea behind Bilateration is that candidate positions calculated from reasonable (i.e., error bounded) anchor positions and distance measurements tend to be close to each other, whereas candidate positions calculated from false anchor positions or distance measurements are highly unlikely to be close to each other if false information are not collaborated. By using ilateration instead of classical multilateration to compute location estimation, Bilateration requires much lower computational complexity, yet still retains the same localization accuracy. This paper also evaluates and compares Bilateration with three multilateration-based localization algorithms, and the simulation results show that Bilateration achieves the best comprehensive performance and is more suitable to real wireless sensor networks.
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Types, structures and theories in NKI
ZHANG Xiaoru, ZHANG Zaiyue, SUI Yuefei
Front. Comput. Sci.. 2008, 2 (4): 451-459.
https://doi.org/10.1007/s11704-008-0032-9
The National Knowledge Infrastructure (NKI) is a multi-domain knowledge base. The classical type theory is no longer appropriate to describe every kind of object in multi-domains, such as artifacts, natural or micro objects. Three different kinds of type theories are defined: the classical, atomic and pseudo type theories; in the classical type theory, two new type constructors are defined: setm and ∨, to describe the types of sets of all the elements of the types and unions of two sets of different types, respectively. The structures and categories in the type theory are defined, and the sub-structures and homomorphic structures are used to describe the part-of relations that give the algebraic specifications for the natural objects and the part-of relations between the natural objects, micro objects and artifacts.
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11 articles
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