1,721,024 research outputs found
A pascal program suitable to solve large sparse linear systems on personal computers
No full textLarge and very sparse linear systems are common in many real problems, such as those involving electrical networks, structural analyses, power distribution systems, nuclear reactor and operational research. In this paper a Pascal program suitable to solve such a kind of problem is given. The program is tailored to be used on personal computers. The code is based on the classical Gauss-Seidel iterative method
Topology in an O-O GIS
No full textTopology is an important kind of knowledge in Geographical Information Systems (GISs). In this paper a small set of user-oriented topological relationships and operators is used as formal background for the implementation of topology on top of the O2 Database Management System (DBMS). Object-oriented (O-O) systems allow to model geometric data and topological relationships thanks to the object identity, the modeling flexibility, the inheritance, and the overriding/overloading features. The representation adopted for the topology is a trade-off between avoiding data redundancy and maintaining database schema independence. Examples of topological queries in O2SQL conclude the paper
Some numerical results about the solution of sparse linear systems
No full textThe paper compares two Pascal programs that solve unsymmetric (very) sparse linear systems by applying, respectively, Gaussian elimination with partial pivoting and Gauss-Jordan reduction. The comparison involves both the CPU times and the storage requirements
Spatial Operators
No full textThis paper discusses issues related to the integration of spatial operators into the new generation of SQL-like query languages. Starting from spatial data models, current spatial extensions of query languages are briefly reviewed and research directions are highlighted. A taxonomy of requirements to be satisfied by spatial operators is proposed with emphasis on users' needs and on the introduction of data uncertainty support. Further, spatial operators are classified into the three important categories of topological, projective, and metric operators and for each of them the state of the art is outlined
Multiparadigm query strategies in object-oriented geographic databases
No full textThe authors discuss three different paradigms suitable for querying object-oriented geographic databases. All together, the paradigms presented constitute the basis of a flexible and easy to use querying environment suitable for different categories of users. The first paradigm, to be adopted by programmer users, is based on the message sending mechanism of object-oriented database programming languages. The second paradigm is a browsing-based technique suitable for not unskilled users who have only a vague idea of the contents of the database. Finally, a frame-based approach is adopted for the third paradigm: this is suitable for non-programmer users who have a specific task to accomplis
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