Fundamenta Informaticae - Volume 53, issue 2

Authors: Amadio, Roberto | Boudol, Gerard | Lhoussaine, Cedric

Article Type: Research Article

Abstract: The message deliverability property requires that every emitted message has a chance of being received. In the context of the asynchronous π-calculus, we introduce a discipline of non-uniform receptivity that entails this property. Adopting this discipline requires a style of programming where resources are persistent. We give a general method to transform (in a fully abstract way) a process so that it complies with the discipline.

Keywords: asynchronous π-calculus, message deliverability, receptivity

Citation: Fundamenta Informaticae, vol. 53, no. 2, pp. 105-129, 2002

Authors: Hwang, Min-Shiang | Lee, Cheng-Ch | Hwang, Shin-Jia

Article Type: Research Article

Abstract: Recently, Hwang and Shi proposed an efficient proxy signature scheme without using one-way hash functions. In their scheme, an original signer needn't send a proxy certificate to a proxy signer through secure channels. However, there are two public key substitution methods that can be used to attack their scheme. In this article, we show that their scheme is vulnerable to the public key substitution attacks.

Keywords: cryptography, digital signature, one-way hash function, proxy signatures

Citation: Fundamenta Informaticae, vol. 53, no. 2, pp. 131-134, 2002

Authors: Järvinen, Jouni

Article Type: Research Article

Abstract: We study rough approximations based on indiscernibility relations which are not necessarily reflexive, symmetric or transitive. For this, we define in a lattice-theoretical setting two maps which mimic the rough approximation operators and note that this setting is suitable also for other operators based on binary relations. Properties of the ordered sets of the upper and the lower approximations of the elements of an atomic Boolean lattice are studied.

Citation: Fundamenta Informaticae, vol. 53, no. 2, pp. 135-153, 2002

Authors: Midelfart, Herman | Komorowski, Jan | Nørsett, Kristin | Yadetie, Fekadu | Sandovik, Arne K. | Lægreid, Astrid

Article Type: Research Article

Abstract: Biological research is currently undergoing a revolution. With the advent of microarray technology the behavior of thousands of genes can be measured simultaneously. This capability opens a wide range of research opportunities in biology, but the technology generates a vast amount of data that cannot be handled manually. Computational analysis is thus a prerequisite for the success of this technology, and research and development of computational tools for microarray analysis are of great importance. One …application of microarray technology is cancer studies where supervised learning may be used for predicting tumor subtypes and clinical parameters. We present a general Rough Set approach for classification of tumor samples analyzed with microarrays. This approach is tested on a data set of gastric tumors, and we develop classifiers for six clinical parameters. One major obstacle in training classifiers from microarray data is that the number of objects is much smaller that the number of attributes. We therefore introduce a feature selection method based on bootstrapping for selecting genes that discriminate significantly between the classes, and study the performance of this method. Moreover, the efficacy of several learning and discretization methods implemented in the ROSETTA system [18] is examined. Their performance is compared to that of linear and quadratic discrimination analysis. The classifiers are also biologically validated. One of the best classifiers is selected for each clinical parameter, and the connection between the genes used in these classifiers and the parameters are compared to the establish knowledge in the biomedical literature. Show more

Keywords: Rough Set, ROSETTA, Gene Expression, cDNA Microarray

Citation: Fundamenta Informaticae, vol. 53, no. 2, pp. 155-183, 2002

Authors: Ţiplea, Ferucio | Mäkinen, Erkki | Trincă, Dragos | Enea, Costel

Article Type: Research Article

Abstract: Time-varying codes associate variable length code words to letters being encoded depending on their positions in the input string. These codes have been introduced in [8] as a proper extension of L codes. This paper is devoted to a further study of time-varying codes. First, we show that adaptive Huffman encodings are special cases of encodings by time-varying codes. Then, we focus on three kinds of characterization results: characterization results based on decompositions over families of …sets of words, a Schützenberger like criterion, and a Sardinas-Patterson like characterization theorem. All of them extend the corresponding characterization results known for classical variable length codes. Show more

Keywords:

Citation: Fundamenta Informaticae, vol. 53, no. 2, pp. 185-198, 2002