Therefore using linux as basic operating system has become a popular solution in embedded operating system 所以利用linux作為底層操作系統(tǒng)成為現(xiàn)在日益流行的嵌入式操作系統(tǒng)的解決方案。
Because of the reason of history , a large amount of various different database that constructed exist on the network , in a lot of respects , there are several the following respects mainly in their different constructing nature behavior : 1 ) the constructing differently of system structure of the computer , each database is running in the mainframe , the microcomputer is , in work station , pc or embedded system ; 2 ) the constructing differently of basic operating system , the basic operating system of each database system can be unix , windows nt , linux . etc . ; 3 ) the constructing differently of dmbs itself can be all oracle of the database system of relation type , sql server , etc . , it can be a database of different data models too , such as relation , mode , level , network , target of facing , the database of function type ; 4 ) the structure of the data and sometime are constructed differently , each different databases are used and adopt different data structure and sometime expression way systematically 隨著internet的發(fā)展,網(wǎng)絡(luò)上存在著大量多樣異構(gòu)的數(shù)據(jù)庫(kù),它們的異構(gòu)性表現(xiàn)在多個(gè)方面,主要有如下幾個(gè)方面: 1 )計(jì)算機(jī)體系結(jié)構(gòu)的異構(gòu),各個(gè)數(shù)據(jù)庫(kù)運(yùn)行在大型機(jī),小型機(jī)、工作站、 pc或嵌入式系統(tǒng)中; 2 )基礎(chǔ)操作系統(tǒng)的異構(gòu),各個(gè)數(shù)據(jù)庫(kù)系統(tǒng)的基礎(chǔ)操作系統(tǒng)可以是unix 、 windowsnt 、 linux等; 3 ) dbms本身的異構(gòu),可以是同為關(guān)系型數(shù)據(jù)庫(kù)系統(tǒng)的oracle 、 sqlserver等,也可以是不同數(shù)據(jù)模型的數(shù)據(jù)庫(kù),如關(guān)系、模式、層次、網(wǎng)絡(luò)、面向?qū)ο?,函?shù)型數(shù)據(jù)庫(kù); 4 )數(shù)據(jù)結(jié)構(gòu)及語(yǔ)義異構(gòu),各個(gè)不同的數(shù)據(jù)庫(kù)應(yīng)用系統(tǒng)采用不同的數(shù)據(jù)結(jié)構(gòu)和語(yǔ)義表達(dá)方式。