Many works studied storage structures of services.Among them, a multilevel index model was proved to be very efficient for service storage for large-scale service repositories.It has the advantages of non-redundancy, stability, being easy managed and maintained.Previous works are proposed and evaluated on the assumption that the probability of service invoking is equal.However, it is too strict in reality, which means the efficiency of service retrieval is not optimal.In order to improve the efficiency of service retrieval under the condition of unequal probability of service invoking, the time complexity of the service retrieval is deduced and an optimal key selection method is proposed according to the function.Our experimental results show that the optimal key selection method reduces 15％ of retrieval time.Therefore, the effectiveness and efficiency of the proposed optimal key selection method under unequal probability of service invoking are valid.%大规模服务存储结构模型研究中, 多级索引模型被证明是非常高效的存储结构, 具有稳定、易管理、易维护、低冗余的优势.目前的研究建立在服务调用概率平均分布这一假设之上, 然而现实服务调用是不等概率的, 这意味着多级索引模型在服务调用的不等概率情况下还不是最优.为提高服务调用不等概率条件下多级索引模型的检索效率, 通过分析多级索引模型的检索特性, 推导出检索操作的时间复杂度函数.利用函数极值, 设计了不等概率条件下键值的优化选择方法.实验结果显示, 该方法比随机选键方法提高检索效率15％左右, 证明优化选择方法能有效提高服务检索效率.
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