query variable 查询变数
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.
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。
Since there are no steps following the variable name, this query expression results in a single node which happens to be the current node.
由于在变量名后面没有任何步骤，因此该查询表达式将产生一个单一节点，即正好是当前的节点。
Notice also that Listing 5 adds a new variable to the query string, env.
还要注意，清单5将一个新的变量添加到查询字符串env。
应用推荐