传统的设施选址问题一般假设所有顾客都被服务，考虑到异常点的存在不仅会增加总费用（设施的开设费用与连接费用之和），也会影响到对其他顾客的服务质量。研究异常点在最终方案中允许不被服务的情况，称之为带有异常点的平方度量设施选址问题。该问题是无容量设施选址问题的推广。问题可描述如下：给定设施集合、顾客集，以及设施开设费用和顾客连接费用，目标是选择设施的子集开设以满足顾客的需求，使得设施开设费用与连接费用之和最小。利用原始对偶技巧设计了近似算法，证明了该算法的近似比是9。

Traditionally, we assume that all the clients to be provided service in the facility location problems. In our study, we explore the case when only a fraction of clients allow to be denied service in the final solution. Indeed, the existence of outliers will not only increase the total cost, but also have an undesirable effect on the service quality of other clients. We consider the squared metric facility location problem with outliers, which is a generalization of the classic uncapacitated facility location problem. Next we will give a detailed description of the problem. Given a set of facilities with open cost and a set of clients with connection costs, we seek a subset of facilities to open and satisfy the demands of clients. The objective is to minimize the sum of total open and connection cost. We utilize the primal-dual scheme to design an approximation algorithm, and prove that the proposed algorithm is a 9-approximation.