First , the idea of how to filter out and minimize unnecessary reads of elements using parent s structural information is introduced , which can be used to accelerate structural joins of parent - child and preceding - sibling - following - sibling relationships . second , two efficient structural join algorithms of sibling relationship are proposed 在此基础上，我们提出了针对结构关系的优化思想：利用双亲的结构信息来过滤和减少对元素无意义的访问的思想，这种思想可以加速双亲-孩子和左兄弟-右兄弟的结构连接。
Main characteristics of dbxi are : 1 ) a new xml numbering scheme is adopted which enables each element in xml documents carries corresponding dtd structural information . 2 ) a path query with n elements ( or attributes ) and a predicate restriction can be implemented with only 0 or 2 structural join operations per xml document while at least n - 1 times of structural join operations are needed in xiss ( xiss is a kin xml indexing system developed by q . li and b . moon ) . 3 ) for a path expression that is not complying with any paths in xml documents , dbxi can give a judgment of no answer in much shorter time than that of sphinx , xiss , etc . experimental results demonstrate that dbxi can process path expressions much faster than lore sphinx and xiss do Dbxi的主要特点是： 1 )采用了新的xml编码方法，使xml文档中每个元素属性的编码携带了相应的dtd结构信息； 2 )对一个由n个元素属性组成的有一个谓词约束的路径表达式， dbxi处理每个xml文档，由同类系统xiss所需的至少n - 1次结构连接运算，降低至0次或2次结构连接运算； 3 )如果查询路径在待查xml文档中不存在正确的匹配结构， dbxi能够在比国际上的sphinx和xiss等xml索引方法较短的时间内给出无查询结果的判断。
These algorithms lead to optimal join performance : nodes that do not participate in the join can be judged beforehand and then skipped using b - tree index . besides , each element list joined is scanned sequentially once at most . furthermore , output of join results is sorted in document order 其次，提出了两个高效的兄弟关系的结构连接算法，这两个算法具有较好的连接性能：不参与连接的结点可以事先判断出来并利用b树跳过，连接的两个列表最多都只需扫描一次，而且连结结果按照文档序有序。
The number of modes should be selected according to the participant coefficient of mode when calculating the internal force by the response spectrum method ; ( 4 ) the roof plate of large base which connect the towers together should be thick enough but not exceeding the proper scope that the towers and the large base can vibrate together , ( 5 ) in structures with large base and muti - towers , with increasing of the capacity of the large base , the inter - story shear force will increase while the inter - story displacement will decrease as to fulfill the ductility request to avoid the large base becoming weak story , but meanwhile , the upper story will turn into weak story , thus the coefficient r s should be within 2 . 0 ~ 3 . 0 采用振型分解反应谱法计算结构内力时应根据振型参与系数选择振型避免漏选；大底盘多塔楼结构连接各塔楼的裙房屋面刚度应做得大些，以保证底部裙房与上部塔楼共同振动，但也不能过刚；大底盘多塔楼结构底盘承载力的加强将使底盘层剪力增大、层间变形减小，但易于满足延性要求，在一定程度上可避免底盘成为薄弱层。但底部加强会导致薄弱层的上移，因此采取提高底盘承载力的措施的效果是有限度的，承载力系数s宜取为2 . 0 3 . 0之间。
