扩展XML-RL查询代数的设计是为了支持具有面向对象特征的查询。
The design of extending XML-RL query algebra is to support the querying with the object-oriented features.
本文简单分析了满足GIS空间查询代数的一般要求，然后形式化地定义了一种适合于GIS空间查询的变量查询代数。
General requirements of spatial query in GIS are briefly outlined in this paper. A Variable query Algebra is formally defined for spatial query of GIS.
XQueC 还设计了用来评估 XML 查询的代数。
XQueC has also designed an algebra for evaluating XML queries.
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