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Decision Support Systems Reports and Theses: Abstracts

Stephan Abramowski and Heinrich Mueller, I-D Queries in 3-D Space, Interner Bericht 9 /85 , Uni- versitaet Kadsruhe, Fakuitaet fuer informatik, 7500 Karlsruhe 1, West Germany, 1985

Matts, Ahisen, Anders Bjoernerstedt and Christer Hulten, OPAL: An Object-Based System for Appli- cation Development, SYSLAB Rep. 38, University of Stockholm, S-lOS 91 Stockholm, Sweden, 1985

We present algorithms for ld queries in 3d space, i.e., algorithms which compute the first object intersected by a query ray q, given a set of objects and q. Such algorithms are needed for the generation of pseudo-realistic images by ray-trac- ing. We say an algorithm has complexity (s(n), t(n)), if it needs space O(s(n)) and query time O(t(n)); n the size of the input, s and t some functions. We restrict to objects bounded by polygons. In special cases, the problem can be transformed to the problem of ld queries in 2d space by perfor- ming some parallel projection. In 2d space, we present a (n,(log n)* *2) algorithm for iso-ori- ented segments intersected by a line and a (n * * 2, log n) algorithm for the general case of pairwise disjoint segments. In 3d space we present an (n**2*log n, (log n)* *4) algorithm for iso-oriented cubes intersected by a plane ( ld query in '2 1/2 d space'), and an ( n * * 3 , (log n)* * 2) algorithm for iso-oriented cubes. Furthermore we present an (n* .6, (logn)* *) algorithm for objects bounded by polygons.

The algorithms often use a sequence of similar sequences; in the appendix, we present a tech- nique for efficiently storing and searching such sequences. We show, that this technique can also be used for an optimal (n, log n) algorithm for point location in curvilinear partitions of 2d space. The algorithms for objects intersected by a line or plane are based on a hierarchy of hulls of the objects (e.g., convex hulls). In the general case, we use the concept of duality and reduce the problem to a point location problem in some space.

Author's Abstract

North-Holland Decision Support Systems 2 (1986) 267-282

Design and implementation of information sys- tems in which requirements on qexibility, system evolution and high-level task support are em- phasized, require suitable design and run-time support. Office systems are one class of systems where this need is apparent today. This paper gives a brief overview of OPAL, a combined run time and application development system, cur- rently being designed at the University of Stock- holm. The paper describes the environment which OPAL is intended for, the overall architecture and the basic system concepts including the object-based model. This is followed by a short discussion of hos this model can be used for application development. The paper ends with a summary and status of the OPAL project.

Author's Abstract

Erik AIIhardt, Institutional Welfare and State In- terventionism in the Scandinavian Countries, Arbe- itspapier 185, J.W. Goethe-Universitaet Frankfurt und Universitaet Mannheim, Sonderforsehungs- bereich 3, West Germany, 1985.

A description of the 'Nordic' or 'Scandinavian' welfare state as well as of the present attitudes towards it requires some understanding of its his- torical roots. In the Scandinavian countries it has been seen as natural and normal that the state intervenes in order to guarantee a modicum of welfare and social security for all. A fairly positive attitude to state interventionism did not suddenly emerge during the 20th century. Rather it devel- oped during centuries under political conditions in which the state came to be conceived largely as a benefactor of the common people.

Author's Abstract

0167-9236/86/$3.50 © 191~6, Elsevier Science Publishers B.V. (North-Holland)