NDLI: QL/G: A Query Language for Geometric Data Bases

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QL/G: A Query Language for Geometric Data Bases

Content Provider	Semantic Scholar
Author	Chan, Edward P. F. Zhu, Rupert Ruopeng
Copyright Year	1996
Abstract	This paper describes a data model and its query language for a database system developed at the University of Waterloo. The system, called QL/G, is designed for managing data in a geometric database. Geometric data types like general regions, lines and points are directly supported as built-in data types in the system. The query language, also called QL/G, is intended to be a general-purpose spatial query language for manipulating both alphanumeric as well as geometric data. The proposed language is a modular, strongly-typed functional language with an SQL avour. It consists of two main categories: geometric and non-geometric operators. Non-geometric operators corresponds to a data retreival language in nested relational database systems. Geometric operators are designed, both syntactically and semantically, to be independent of non-geometric operators. This intends to achieve the objective that the set of geometric operators be independent of, but incorporable into, any existing set-oriented data models. The semantics of geometric operators are formally de ned and data types are closed under the proposed operators. The geometric operators are also designed to be as generic and general as possible, and are implemented with state-of-the-art computational geometry algorithms. The query language can be viewed as a generalization of existing proposals, and most of the geometric operators proposed in the literature could be expressed with the language. To facilitate the evolution of applications and to tailor to individual need, a function de nition mechanism is available for de ning new operators expressible by the language. Examples are used throughout to illustrate and motivate the constructs proposed in the language.
File Format	PDF HTM / HTML
Alternate Webpage(s)	http://kbl.uwaterloo.ca/qlg.ps
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article

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