两种主流空间数据库国际标准与应用分析

An Analytical Study of Two International Standards for Spatial Database

空间数据库标准在数据库空间扩展过程中发挥着重要作用。基于SQL的简单要素访问(Simple Feature Access-Part 2:SQL option,SFA SQL)和SQL多媒体与应用程序包第三部分空间(SQL Multimedia and Application Packages-Part 3:Spatial,SQL/MM Spatial),是目前两种主流的空间数据库国际标准,在地理信息系统(GIS)和数据库行业得到广泛的遵循。本文主要研究了这两种标准,首先,着重从几何对象模型和要素表实现模式两方面内容进行阐述。除了几何对象模型,SFA SQL中还定义了文本标注对象模型,SQL/MM Spatial根据自身特色也定义了方向和角度对象模型。要素表的实现模式决定了要素在数据库中的存储方式,SFA SQL有两种要素表的实现模式:预定义数据类型方式和扩展Geometry类型方式,SQL/MM Spatial只定义了扩展Geometry类型的实现方式。然后,对两种标准进行了对比分析,为空间数据库SQL标准的选择提供一定的参考依据。两种标准在扩展环境、对象模型、空间函数几个方面存在一些差别,但通过对其发展历史的研究和趋势分析,这种差别将越来越小。最后,通过调查分析了两种标准在空间数据库产品中的应用现状和问题。

Spatial database standard plays an important role in design and implementation of spatial database. SFA SQL （ Simple Feature Access-Part 2 ： SQL option） and SQL/MM Spatial （ SQL Multimedia and Application Packa- ges-Part 3 ： Spatial） have been widely adopted in many spatial databases and GIS software, because they stand for the trend of SQL standards in the future. This article described and analyzed the two standards, compared them from several aspects, therefore, provided reference in choosing the SQL standard for spatial database. Firstly, the article mainly focused on the Geometry object model and the feature table implementation schema of the two stand- ards. Besides the Geometry object model, SFA SQL also defined the text object model, and the SQL/MM ：Spatial al- so defined the direction and angle object model. The feature table implementation schema determined the feature storage model on database. SFA SQL described two sorts of implementation. One is implementations based a more classical SQL relational model using only the SQL predefined data types and the other is extending SQL with additional types for geometry. SQL/MM only described the implementation schema of extending SQL with additional types for geometry. The mechanism for extending the type system of an SQL implementation is through the definition of User Defined Types （UDT）. Secondly,the article focused on the difference of the two standards and compared them from three aspects ： （ 1 ） the SQL-implementation environment; （2） the Geometry object model; （ 3 ） the rou- tines to support geometric behavior and query. SFA SQL can be implemented in the predefined data type SQL 92 environment and UDT environment. The SQL/MM：Spatial can only be implemented in UDT environment. SQL/MM defined geometry types using circular interpolation and linear interpolation and SFA SQL only using linear interpo- lation. The geometric routine type in SQL/MM is richer than SFA SQL and the definition is more specific. Finally, the article surveyed the standardization state of seven popular spatial situation of the spatial database standards; predicted the trend of the database products, overviewed the application application requirement.