CAD-tietokannat

Tämä pro gradu -tutkielma on kirjallisuuskatsaus CAD-tietokannoista. CAD (Computer-Aided Design) tarkoittaa tietokoneavusteista suunnittelua. CAD-ohjelmilla mallinnettavat objektit ovat tyypillisesti monimutkaisia rakenteeltaan. Niissä on toisiinsa yhteydessä olevia entiteettejä, ja niiden rakenne on usein hierarkkista. Objektit voivat olla koottuja objekteja, jotka sisältävät toisia objekteja. Tämä aikaansaa tietokannalle erityisiä vaatimuksia. CAD-tietokannan tulee pystyä käsittelemään suuria datamääriä, ja datan monimutkaiset keskinäiset suhteet ovat esitettävä riittävästi. Tietokannan täytyy pystyä käsittelemään datan dynaamista luonnetta. Tämä johtuu siitä, että käyttäjä voi suunnitteluprosessin edetessä määritellä uusia dataluokkia ja muuttaa niitä. Tietokannan tulee myös muun muassa olla riittävän joustava, tukea eri versioita ja huolehtia datan eheydestä. Rajoitusten käsittelykin on yleensä poikkeuksellista CAD-tietokannoissa, johtuen muun muassa poikkeuksellisen pitkistä tapahtumasarjoista. Yleisimmät CAD-järjestelmissä käytettävät tietokantamallit ovat hierarkkinen, verkkomallin, relaatio-, oliomallin ja olio-relaatiomallin tietokanta. Näissä kaikissa malleissa on hyvät ja huonot puolensa. Hierarkkista ja verkkomallin tietokantoja käytetään edelleen, vaikka ne ovat vanhoja. Relaatiotietokantaa pidetään hierarkkista ja verkkomallin tietokantoja parempana muun muassa sen loogisuuden ja yksinkertaisuuden takia. Oliomallin tietokantaa pidetään monissa lähteissä parhaana CAD-järjestelmiin. Se ei kuitenkaan ole syrjäyttänyt muita tietokantamalleja

Graphical modelling of modular machines

This research is aimed at advancing machine design through specifying and implementing (in "proof of concept" form) a set of tools which graphically model modular machines. The tools allow mechanical building elements (or machine modules) to be selected and configured together in a highly flexible manner so that operation of the chosen configuration can be simulated and performance properties evaluated. Implementation of the tools has involved an extension in capability of a proprietary robot simulation system. This research has resulted in a general approach to graphically modelling manufacturing machines built from modular elements. A focus of study has been on a decomposition of machine functionality leading to the establishment of a library of modular machine primitives. This provides a useful source of commonly required machine building elements for use by machine designers. Study has also focussed on the generation of machine configuration tools which facilitate the construction of a simulation model and ultimately the physical machine itself. Simulation aspects of machine control are also considered which depict methods of manipulating a machine model in the simulation phase. In addition methods of achieving machine programming have been considered which specify the machine and its operational tasks. Means of adopting common information data structures are also considered which can facilitate interfacing with other systems, including the physical machine system constructed as an issue of the simulation phase. Each of these study areas is addressed in its own context, but collectively they provide a means of creating a complete modular machine design environment which can provide significant assistance to machine designers. Part of the methodology employed in the study is based on the use of the discrete event simulation technique. To easily and effectively describe a modular machine and its activity in a simulation model, a hierarchical ring and tree data structure has been designed and implemented. The modularity and reconfigurability are accommodated by the data structure, and homogeneous transformations are adopted to determine the spatial location and orientation of each of the machine elements. A three-level machine task programming approach is used to describe the machine's activities. A common data format method is used to interface the machine design environment with the physical machine and other building blocks of manufacturing systems (such as CAD systems) where systems integration approaches can lead to enhanced product realisation. The study concludes that a modular machine design environment can be created by employing the graphical simulation approach together with a set of comprehensive configuration. tools. A generic framework has been derived which outlines the way in which machine design environments can be constructed and suggestions are made as to how the proof of concept design environment implemented in this study can be advanced

Data bases and data base systems related to NASA's aerospace program. A bibliography with indexes

This bibliography lists 1778 reports, articles, and other documents introduced into the NASA scientific and technical information system, 1975 through 1980

Workshop on Database Programming Languages

These are the revised proceedings of the Workshop on Database Programming Languages held at Roscoff, Finistère, France in September of 1987. The last few years have seen an enormous activity in the development of new programming languages and new programming environments for databases. The purpose of the workshop was to bring together researchers from both databases and programming languages to discuss recent developments in the two areas in the hope of overcoming some of the obstacles that appear to prevent the construction of a uniform database programming environment. The workshop, which follows a previous workshop held in Appin, Scotland in 1985, was extremely successful. The organizers were delighted with both the quality and volume of the submissions for this meeting, and it was regrettable that more papers could not be accepted. Both the stimulating discussions and the excellent food and scenery of the Brittany coast made the meeting thoroughly enjoyable. There were three main foci for this workshop: the type systems suitable for databases (especially object-oriented and complex-object databases,) the representation and manipulation of persistent structures, and extensions to deductive databases that allow for more general and flexible programming. Many of the papers describe recent results, or work in progress, and are indicative of the latest research trends in database programming languages. The organizers are extremely grateful for the financial support given by CRAI (Italy), Altaïr (France) and AT&T (USA). We would also like to acknowledge the organizational help provided by Florence Deshors, Hélène Gans and Pauline Turcaud of Altaïr, and by Karen Carter of the University of Pennsylvania

Secondary storage management in an object-oriented database management system

Ankara : The Department of Computer Engineering and Information Sciences and the Institute of Engineering and Sciences of Bilkent Univ. , 1988.Thesis (Master's) -- Bilkent University, 1988.Includes bibliographical references leaves 91-95.In this thesis, a survey on object-orientation and object-oriented database management systems has been carried out and a secondary storage management and indexing module is implemented for an object-oriented database management system prototype developed at Bilkent University. First, basic concepts, characteristics, and application areas of objectoriented approach are introduced, then, the designed prototype system is presented, the secondary storage management module is explained in detail and the functions of the other modules are summarized. Finally, the current research issues in the object-oriented database systems are introduced.Karaorman, MuratM.S