兰州大学信息学院计算机应用所.pptVIP

Spatio-temporal Models and Languages: An Approach Based on Data Types (I) 王涛 2008.4.28 兰州大学信息学院计算机应用所 An Abstract Model Overview of Data Type Operations The design of the operations adheres to three principles: (i) Design operations as generic as possible. (ii) Achieve consistency between operations on non-temporal and temporal types. (iii) Capture the interesting phenomena. An Abstract Model Operations on Non-temporal Types 兰州大学信息学院计算机应用所 An Abstract Model Operations on Non-temporal Types 兰州大学信息学院计算机应用所 An Abstract Model Operations on Non-temporal Types Example1. We introduce the following example relations for use within this section, representing cities, countries, rivers, and highways in Europe. city (name: string, pop:int, center:point) country (name: string, area: region) river (name:string, route:line) highway (name:string,route:line) 兰州大学信息学院计算机应用所 An Abstract Model Operations on Non-temporal Types Notations for Signatures. The notations for signatures used when defining the data type operations next are partly based on Table4.4. We let π and σ be type variables that range over all point and point set types of Table4.4, respectively. If several type variables occur in a signature (e.g., for binary operations), then they are assumed to range over types of the same space. For example, in signatureπ×σ→α we can select one-dimensional space Integer and instantiateπto int andσto range(int); or we can select two-dimensional space 2D and then instantiateπto point andσto either points, line, or region. 兰州大学信息学院计算机应用所 An Abstract Model Operations on Non-temporal Types In signatureσ×σ→α, both arguments have to be the same type. However, in signature σ1×σ2→α, ty