中文摘要：

文中为对象代理数据库提出了一种新的索引结构——路径导航索引（Path Navigation Index,PNI）,能够克服路径表达式计算开销大的缺点,使对象代理数据库跨类查询与代理对象查询具备高效的查询性能.PNI索引建立在代理层次的路径实例之上,包括Path-Instance-Table,Identity-Index和Attribute-Index3个组成部分.Path-Instance-Table能够物化存储路径实例,避免查询处理过程中冗余的对象导航遍历.Identity-Index与Attrib-ute-Index用于对路径实例进行关联检索,能够避免对象导航过程中的条件判断.通过实验分析了影响路径表达式计算的不同因素,实验结果表明,利用PNI索引计算路径表达式的方法在多数情况下性能要优于现有计算方法,尤其适用于带谓词的路径表达式计算.

英文摘要：

This paper proposes an index structure：Path Navigation Index（PNI）,which can reduce the cost of evaluating path expression,leading to efficient query processing of cross-class query and deputy object query in object deputy database.Path Navigation Index consists of Path-Instance-Table,Identity-Index and Attribute-Index.Path instances are materialized in Path-Instance-Table,avoiding redundant object traversal in query processing.Identity-Index and Attribute-Index facilitate associative search of path instances,avoiding predicate evaluation during object traversal.The experiments are used to analyze the influential factors of path expression evaluation,and the experimental results demonstrate that evaluation of path expression with this index outperforms the other methods in most cases,especially for the path expressions with predicate conditions.