Abstract: This paper discusses the cost models for spatial joins based on R-Tree, and researches the cost model for spatial joins proposed byHUANG Y W. This paper reduces the time complexity by using the best or worst selective strategy, and an improved function of estimating ispresented which is about the cost model based on buffering. The experiment shows that the accuracy of estimating by the improved model is betterthan the primary model.

Key words: R-Tree; Spatial joins; Cost model; Window query

摘要： 对基于R-Tree 的空间连接代价模型进行了探讨，主要研究了HUANG Y W 提出的空间连接代价模型。利用最优/最差选择策略降低该算法的时间复杂度，对基于缓冲区的代价模型提出了改进后的评估公式，通过实验验证了改进后的模型比原模型提高了评估的精确度。

关键词: R-Tree；空间连接；代价模型；窗口查询