The availability of central reference information as thesauri is critical for correct intellectual access to distributed databases, in particular to digital collections in international networks. There is a continuous raise in interest in thesauri, and several thesaurus management systems have appeared on the market. The issue, how to integrate effectively such central resources into a multitud...

block method based on Backward Differentiation Formulae (BDF) of variable step size for solving first order stiff initial value problems (IVPs) for Ordinary Differential Equations (ODEs). In a 2-point Block Backward Differentiation Formula (BBDF), two solution values are produced simultaneously. Plots of their regions of absolute stability for the method are also presented. The efficiency of th...

The work on Conceptual Modelling performed by our group at PUCRio is surveyed, covering four mutually dependent research topics. Regarding databases as a component of information systems, we extended the scope of the Entity-Relationship model, so as to encompass facts, events and agents in a three-schemata specification method employing a logic programming formalism. Next we proceeded to render...