https://ir.unisa.ac.za/handle/10500/23881 Sat, 02 May 2026 15:30:00 GMT 2026-05-02T15:30:00Z https://ir.unisa.ac.za/handle/10500/24067 A model checker for transition systems De Villiers, PJA A model checker automatically determines whether a model of a reactive system satisfies its specification. Temporal logic is used to specify the intended behaviour of a reactive system which is modelled as a transition system. Fast state space exploration is mandatory, the main problem being to determine the uniqueness of each newly generated state. Traditional model checkers can analyse about 104 states in an acceptable amount of time. A model checker which incorporates three new ideas has been implemented. (1) A bit vector technique used by Holzmann in a fast protocol validation system is combined with model checking to produce a system capable of analysing about 101 reachable states. (2) Since state spaces are sparse and clustered, larger problems are handled by using paging techniques. (3) Traditional model checkers often search subspaces unnecessarily when temporal operators are nested. A top-down technique called subproblem detection is used which avoids this. Wed, 01 Jan 1992 00:00:00 GMT https://ir.unisa.ac.za/handle/10500/24067 1992-01-01T00:00:00Z https://ir.unisa.ac.za/handle/10500/24066 PEW: A tool for the automated performance analysis of protocols Wheeler, G; Kritzinger, Pieter S. The Protocol Engineering Workbench (PEW) is an integrated software system or tool for the analysis of communication protocols specified using the Estelle Formal Description Technique or FDT. The execution of systems specified in Estelle are simulated and data about the execution are gathered in the process. The PEW is thus aimed primarily at the performance analysis of such systems but, by virtue of the simulated execution, also ensures that some correctness errors will be detected. The paper describes the design philosophy and various components of the PEW as well as the facilities it provides for data collection and performance analysis. Pan of the data gathered is the Markovian transition probability matrix where each transition in the protocol system is considered to be a state in a semi-Markov chain describing the protocol system execution. Wed, 01 Jan 1992 00:00:00 GMT https://ir.unisa.ac.za/handle/10500/24066 1992-01-01T00:00:00Z https://ir.unisa.ac.za/handle/10500/24065 Beam search in attribute-based concept induction Theron, H; Cloete, I Thi spaper investigates the issues of specializing only a single best conjunction to employing a beam search when learning attribute-based concept descriptions using the GCA algorithm. We describe GCA, a recently introduced generic learning algorithm which generalizes a number of well-known learning algorithms like CN2 and AQ. It is shown, using ten test domains, that concept descriptions found by a beam search are seldom more accurate than those found by specializing only a single best conjunction. In addition, the former descriptions are usually more complex than the latter and in some cases even considerably more so. This result holds even when more stringent pruning is applied during a beam search. Since specializing only one conjunction is computationally much less demanding than specializing a set of alternative best conjunctions, the result is that GCA need not employ a beam search in order to find good descriptions. Wed, 01 Jan 1992 00:00:00 GMT https://ir.unisa.ac.za/handle/10500/24065 1992-01-01T00:00:00Z https://ir.unisa.ac.za/handle/10500/24064 An evaluation of the skill requirements of entry-level graduates in the information systems industry Smith, DC; Newton, S; Riley, MJ Information Systems (IS), although a relatively new academic discipline, is receiving considerable attention in tertiary institutions in South Africa. Despite this, there is currently no standard curricula for IS graduates or diplomates. A research project· was conducted in 1991 to identify the skills of IS graduates leaving tertiary institutions and the skills required by industry. A sample of 33 IS professionals and 15 IS academics completed a questionnaire covering practical skills levels and theoretical knowledge levels. Analysis of the results showed that there were significant differences between academics and industry samples in important skills and knowledge areas. These differences relate to hardware skills and inter-personal skills. There were also significant disagreements within the groups regarding the skill requirements of entry-level graduates. An initiative to bring industry and academics closer together in curricula design and course accreditation is suggested. Wed, 01 Jan 1992 00:00:00 GMT https://ir.unisa.ac.za/handle/10500/24064 1992-01-01T00:00:00Z