Fundamenta Informaticae - Volume 41, issue 4

Authors: Bos, V. | Kleijn, J.J.T.

Article Type: Research Article

Abstract: The formal language χ Core is derived from the systems engineering specification language χ. The language has its roots in Mechanical Engineering where it was designed to specify and analyse production systems. These production systems are described by concurrent communicating processes and can be analysed with the χ simulator. χ Core is a formalisation and simplification of the semantics of the χ language. Our motivation to design χ Core is the lack of a properly defined semantics of the χ specification language itself and the need for improved opportunities for the analysis of production systems. The operational semantics of χ …Core is defined in a standard SOS-style. A bisimulation on χ Core processes is defined and shown to be a congruence. Based on this bisimulation, properties and time aspects of χ Core processes are discussed. The relation between χ and χ Core is explained by means of a translation scheme. Finally, an example specification of a production system is given and conclusions are drawn. Show more

DOI: 10.3233/FI-2000-41401

Citation: Fundamenta Informaticae, vol. 41, no. 4, pp. 367-392, 2000

Authors: Formato, Ferrante | Gerla, Giangiacomo | Sessa, Maria I.

Article Type: Research Article

Abstract: Unification plays a central rule in Logic Programming. We ”soften” the unification process by admitting that two first order expressions can be ”similar” up to a certain degree and not necessarly identical. An extension of the classical unification theory is proposed accordingly. Indeed, in our approach, inspirated by the unification algorithm of Martelli-Montanari, the systems of equations go through a series of ”sound” transformations until a solvable form is found yielding a substitution that is proved to be a most general extended unifier for the given system of equations.

DOI: 10.3233/FI-2000-41402

Citation: Fundamenta Informaticae, vol. 41, no. 4, pp. 393-414, 2000

Authors: Hanisch, H.-M. | Lüder, A.

Article Type: Research Article

Abstract: Petri nets have a longstanding history in controller design and implementation, and it is often told that they have the dominating position in this field due to the close relationship between Petri nets and Graphcet or other sequential function diagrams. We want to show that there are some severe problems when Petri nets are used to describe both: the controller and the plant under control. The nature of these problems is the lack of a concept of input and output signals and, moreover, the lack of a formal concept to interconnect systems modeled by Petri nets via signals. Although this …is often neglected, it turns out to be a key issue if a model of the closed-loop behavior must be established as a precondition for formal controller verification. We present a signal extension for Petri nets and means for interconnecting an arbitrary number of those extended Petri nets. We come up with the conclusion that the resulting models are suited for controller verification. Although the graphical appearance shows similarities to Petri nets, the resulting models are no longer Petri nets. Show more

Keywords: Controller verification, Discrete event systems, Petri nets

DOI: 10.3233/FI-2000-41403

Citation: Fundamenta Informaticae, vol. 41, no. 4, pp. 415-431, 2000

Authors: Michalski, Ryszard S. | Kaufman, Kenneth A.

Article Type: Research Article

Abstract: Knowledge scouts are software agents that autonomously synthesize user-oriented knowledge (target knowledge) from information present in local or distributed databases. A knowledge generation metalanguage, KGL, is used to creating scripts defining such knowledge scouts. Knowledge scouts operate in an inductive database, by which we mean a database system in which conventional data and knowledge management operators are integrated with a wide range of data mining and inductive inference operators. Discovered knowledge is represented in two forms: (1) attributional rules, which are rules in attributional calculus—a logic-based language between prepositional and predicate calculus, and (2) association graphs, which graphically and abstractly …represent relations expressed by the rules. These graphs can depict multi-argument relationships among different concepts, with a visual indication of the relative strength of each dependency. Presented ideas are illustrated by two simple knowledge scouts, one that seeks relations among lifestyles, environmental conditions, symptoms and diseases in a large medical database, and another that searches for patterns of children's behavior in the National Youth Survey database. The preliminary results indicate a high potential utility of this methodology for deriving knowledge from databases. Show more

Keywords: data mining, knowledge discovery, knowledge scouts, inductive databases, knowledge visualization, knowledge generation language, association graphs, attributional calculus

DOI: 10.3233/FI-2000-41404

Citation: Fundamenta Informaticae, vol. 41, no. 4, pp. 433-447, 2000

Authors: Moshkov, Mikhail

Article Type: Research Article

Abstract: In this paper the problem of recognition of words with fixed length from a regular language is considered. The word under consideration can be interpreted as a description of certain screen image in the following way: the i-th letter of the word encodes the color of the i-th screen cell. In this case a decision tree which recognizes some words may be interpreted as an algorithm for the recognition of images which are defined by considered words. The classification of all regular languages depending on the growth of minimal depth of decision trees for language word recognition with the growth …of the word length is obtained. In proofs methods of test theory and rough set theory are used. Show more

DOI: 10.3233/FI-2000-41405

Citation: Fundamenta Informaticae, vol. 41, no. 4, pp. 449-461, 2000