https://ir.unisa.ac.za/handle/10500/23879 2026-05-05T15:11:41Z https://ir.unisa.ac.za/handle/10500/23967 Using statecharts to design and specify a direct-manipulation user interface Van Zijl, L; Mitton, D Statecharts were developed by Harel et al [10] to specify complex reactive systems. In this paper we report on our application of statecharts as a design and specification tool for an X-Windows based Graphical User Interface for the telephone network performance modelling tool GMA. 1992-01-01T00:00:00Z https://ir.unisa.ac.za/handle/10500/23966 Efficient evaluation of regular path programs Wood, PT The next generation of query languages for database systems should have the ability to express recursive queries, the efficient evaluation of which will be crucial to the success of these systems. One such query language which has been the subject of much research is Datalog. We define a class of Datalog programs, namely, the regular path programs, which can always be evaluated efficiently, in particular, when constants are present in a query. Efficient evaluation is ensured by reducing the number of arguments appearing in each predicate defined in the program. The class of regular path programs is incomparable to previous classes to which the technique of argument reduction has been applied. 1992-01-01T00:00:00Z https://ir.unisa.ac.za/handle/10500/23965 Extending local recovery techniques for distributed databases Viktor, HL; Rennhackkamp, MH The most frequently used local database system failure recovery techniques are logging , shadowing and differential files. In a distributed database these local system failure recovery techniques may be·utilized for recovery from a single site failure. However, these techniques need to be extended to facilitate continued distributed executions. Various extended local system failure recovery techniques are presented. The results of a comparison of these techniques are shown. It is concluded the deferred data item logging technique proves to be the best for the system under consideration. 1992-01-01T00:00:00Z https://ir.unisa.ac.za/handle/10500/23964 Integrating similarity-based and explanation-based learning Oosthuizen, GD; Avenant, C Recently, there have been various attempts to combine the strengths of similarity-based learning (SBL) and explanation­-based learning (EBL) in a single learning system. We describe a graph-based learning method called Graph Induction, which is based on the graphical representation of a formal lattice and supports both supervised and unsupervised learning. The method integrates SBL with a weak.form of EBL in such a way that the two mechanisms become totally blended. The result is a unified algorithm with both SBL and EBL involved in each step. The domain theory is generated and/or extended as SBL proceeds and employed immediately, through EBL, to guard further learning and thus control the size of the lattice which otherwise has the potential for increasing exponentially. 1992-01-01T00:00:00Z