数据库 专业英语翻译(12)

数据库专业英语翻译

system. But in what is the development direction of the new database system, industry once is quite confused. The influence of agitation by technology at the time, for quite some time, people put a lot of energy spent on research "object-oriented database system (object oriented database)" or simply as "OO database system". What is worth mentioning, the United States Stonebraker professor proposed object-oriented RDS theory once favored by industry. And in Stonebraker himself Informix spend big money was then appointed technology director always.

However, several years of development, spatio-temporal object-oriented relational database system product market development situation is not good. Theoretically perfect sex didn't bring market warm response. The main reason of success, the main design thought database products with new database system is an attempt to replace the existing database system. This for many has been using database system for years and accumulated the massive job data, especially big customer for customers, is unable to withstand the conversion between old and new data that huge workload and big spending. In addition, object-oriented RDS system makes query language extremely complex, so whether database development businessman or application customers depending on the complicated application technology to be a dangerous road.

Basic structure

The basic structure of database, reflects the three levels of observation database of three different Angle.

(1) physical data layer.

It is the most lining, is database on physical storage equipment actually stored data collection. These data are raw data, the object, the user is processed by internal model describing the throne of handled the instructions of string, character and word.

(2) conceptual data layer.

It is a layer of database, is among the whole logic said. Database Points out the logic of each data definition and the logical connection between data collection of storage and record, is. It is related to the database all objects logical relationship, not their physical condition, is under the database administrator concept of database.

(3) logical data layer.

It is the user sees and use the database, says one or some specific users use collections of data, namely the logical record set.

Database different levels is the connection between conversion by mapping. Main features

(1) to implement the data sharing.

Data sharing contains all users can also access database data, including the