884.txt

This complete matlab for neural network

发信人: fervvac (高远), 信区: DataMining
标  题: Re: 数据仓库里的实体化视图怎么实现？
发信站: 南京大学小百合站 (Wed Sep 11 14:33:12 2002), 站内信件

For any serious implementation, it is a bad idea to store data in text 
format. 

First of all, you need to know which type of system you have, ROLAP or MOLAP.
Chunk is only used in MOLAP, and relations are only used in ROLAP.

The basic method to store data in ROLAP is to store them in relational table(s).
You can either create a table with all dimension attributes  pulus the measure
attribture, or use multiple tables, each for a cuboid. So there is no 
fundamental difficulty  there.


For chunks, I am not sure of the real implementation of commercial systems.
For most prototype systems, the problem is that "extra-long" integer type 
and its efficient calculation is needed. Space trade-off is another issue.
Moreoever, there is an issue of choosing an appropriate compression method.
 
【 在 netsaint (大圣) 的大作中提到: 】
: 我指的是物理存储模式，目前有很多都是用chunk方式，但这样实现起来比较难的
: 如果直接存放在关系表里，那对不同的维的组合就有一个值，表的字段不好统一设定
: 我想（把那些综合数据）存放在一个临时文件里如.txt里，好像更麻烦了
: 【 在 fervvac 的大作中提到: 】
: : What is your question?
: : To compute the MV, you simple modify existing cube computation algorithms ..
: : skip those cuboids that do not need to be materialized. The modification is
: : straigh-forward for both top-down and bottom-up algorithms.
: : If you are asking for the physcial storage format, I think the commercial 
: : systems still store the data in relational tables.
: : There is another line of approaches that use multidimensional model for th..
: : cube/cuboids. They store the pre-computed results in chunks.
: : 【 在 netsaint (大圣) 的大作中提到: 】


--
※ 来源:．南京大学小百合站 bbs.nju.edu.cn．[FROM: 饮水思源BBS]