Otto Mayer

A robust and efficient spatial data structure: the nested interpolation-based grid file

A new structure for organizing a set of multidimensional points called the nested interpolation-based grid file (NIBGF) is introduced. The structure represents a synthesis and an improvement over interpolation-based grid files (IBGF), BANG files, andK-D-B-trees. It decomposes the data search space into uniquely identifiable regions which may either be disjoint as in interpolation-based grid files or enclose each other as in the BANG files. In addition to possessing the symmetry of access and clustering properties characteristic of grid file structures, the performance of NIBGF is comparable to aB-tree performance as far as the index is concerned, even in the worst case scenario, and to the BANG file performance as far as the data regions are concerned. These properties make the new structure suitable for efficient implementation of relational database operations.

On strict interpretations of grammar forms

Strict interpretations of grammar forms are studied with respect to parsing, ambiguity, and decidability for intersection and containment. In particular, a parsing procedure for an arbitrary strict interpretation grammar is given which is based on a given parsing method for the master grammar. Time and space bounds on the new procedure are then obtained. Each ambiguous interpretation grammar of an unambiguous grammar form can be converted to an equivalent unambiguous interpretation of the same grammar form. Unambiguity is always decidable for strict interpretation grammars of unambiguous grammar forms. Also, for languages obtained from “compatible” strict interpretations of an unambiguous grammar form, the following problems are solvable: empty intersection, finite intersection, containment, and equality.

On deterministic canonical bottom-up-parsing

A general framework for producing deterministic canonical bottom-up parsers which contains all these parsers as special cases is described. Then general conditions on the means of construction which guarantee that the obtained parsing methods work correctly are presented. These conditions cover all types of deterministic canonical bottom-up parsers. Based on these conditions a strategy that constructs an optimally adjusted bottom-up parser for a given grammar is discussed.

ilona: an advanced cai tutorial system for the fundamentals of logic

Abstract An advanced tutorial system for teaching the fundamentals of logic has been developed to run on unix work stations and commonly available microcomputers. An important part of this tutorial is the intelligent problem solving environment which allows students to practise writing logical sentences in mathematical notation. A natural language system for intelligent logic narrative analysis ( ilona ) allows students to type in their own logical sentences in plain English and then have the computer check their working when they write these in mathematical form. ilona is an intelligent tutoring system which allows students a great deal of initiative in problem solving and provides a degree of flexibility in answer evaluation not found in traditional cai systems. The concepts and structures used in the development of ilona are easily transferable to other domains.

Concurrency Control in the Interpolation-Based Grid File

The problem of supporting concurrent operations in Interpolation-Based Grid Files is studied. A systematic method for detecting conflict between processes is defined based on the organizational properties of this type of files. One important characteristic of these structures is the dynamic partitioning of the data space into regions and assignment of a unique identifier to each region. This identifier acts then as a surrogate for the region and its spatial properties. High process throughput is achieved by optimizing the number of locked regions. We show that only one or two locks are required in general and the probability that three locks become necessary is negligible. Algorithms to search for, to insert and delete data elements are presented and shown to be correct, deadlock free, and non-preemptive based on the restrictions imposed on the locking order and the reachability mechanism. Furthermore, we present a compression procedure that provides storage maintenance of the data structure. In our scheme, all processes readers, inserters, deleters and compressors can overtake each other.

A framework for producing deterministic canonical bottom-up parsers

A general framework for producing deterministic canonical bottom-up parsers is described and very general conditions on the means of construction are presented which guarantee that the parsing methods work correctly. These conditions cover all known types of deterministic canonical bottom-up-parsers.

Canonical Bottom-up Parsing

A general theory of canonical bottom-up analysis is presented; it includes the familiar types of deterministic bottom-up parsing methods (e.g. precedence, bounded right context, LR, and LR-regular) as special cases. Among the results obtained are sufficient conditions on the means of construction to guarantee the resulting bottom-up-parsing method being deterministic.