This paper proposes an adaptive structural index: AS-Index (adaptive structural index), which can avoid the problem of the existing indexes. AS-Index is based on F&B-Index. It consists of F&B-Index, Query-Table and Part-Table. Frequent queries are kept in Query-Table avoiding redundant operations in query processing. Based on Query-Table an efficient bottom-up query processing is also proposed for answering infrequent queries using the frequent queries in Query-Table. Part-Table is used for optimizing the queries with descendant edges. The existing adaptive structural indexes need to traverse the whole document for adaptation, and their adaptation granularity is XML element node. For AS-Index, the adaptation granularity is F&B-Index node which includes a set of XML element nodes, and its adaptation is an efficient and incremental process that supports branch queries. The experimental results demonstrate that this index significantly outperforms the previous structural indexes in terms of query processing and adaptation efficiencies. For large XML documents, compared with the existing adaptive structural indexes, AS-Index is more scalable%提出了一种新的自适应结构索引:AS-Index(adaptive structural index),能够克服现有静态索引和自适应索引的缺陷,具备高效的查询和调整性能.AS-Index建立在F&B-Index的基础之上,其索引结构包括F&B-Index,Query- Table和Part-Table.Query-Table能够记录频繁查询,避免了查询过程中的冗余操作.并且,在Query-Table的基础上提出了自底向上的查询处理过程,能够充分利用现有的频繁查询高效地回答非频繁查询.Part-Table用于优化包含祖先后裔边的查询,进一步提高了查询性能.现有的自适应结构索引的调整粒度是XML元素节点,调整过程往往需要遍历整个文档.而AS-Index是基于F&B-Index节点的增量调整,其过程是局部的,高效的,并且能够支持复杂分支查询的调整.实验结果表明,AS-Index在查询和调整性能上优于现有的XML结构索引.同时,相比于现有的自适应结构索引,AS-Index针对大规模文档具有更加优良的可扩展性.
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