DB Projects Help>>DBMS architecture & data independence
Collection control techniques are complicated programs which were often formulated and optimized over years. From the perspective of the customer, however, most of them have a quite identical primary structure. The conversation of this primary structure shall help to comprehend the network with information which and the introduction ally to this element postulated 'data independence' of the database technique.
Three-Scheme Architecture
Knowing about the conceptual and the made sensible construction (discussed in model Collection Models, Plans and Instances this model describes two additional schemes - the exterior construction and the inner construction - which help to understand the DBMS construction.
外部方案：
An exterior details construction represents the details about the customer perspective of particular people (single people and customer groups) and the particular techniques and demands connected with these details. (Translated) (ZEHNDER 1998)
Internal Scheme:
内部细节构建代表了详细信息的内容以及用于DBMS功能的所需服务功能。（翻译）（Zehnder 1998）
Therefore, the inner construction represents the details from a perspective very close to the computer or system in general. It does the sensible construction with details specialized aspects like storage space techniques or help functions for more overall performance.
The right hand side of the manifestation above is also called the three-scheme architecture: inner, sensible and external scheme.
While the inner construction represents the actual collection of the details and the use of the storage space, the sensible construction (derived from the conceptual scheme) represents the basic engineering of the details construction. The exterior construction of a particular request, generally, only features that part of the sensible construction which is relevant for its request. Therefore, a database has exactly one inner and one sensible construction but may have several exterior schemes for several programs using this database.
三室结构的目的是从实际数据库中的客户计划离婚，即保存的详细信息。以物理形式，细节仅在内部层面上存在，而其他形式的表现形式则分别确定或在需要时进行。DBM的任务是了解每个级别之间的这种表现。
Data Independence
With knowledge about the three-scheme structure the term information self-reliance can be revealed as followed: Each advanced of the information structure is safe from changes of the next lower degree of the structure.
Physical Independence:
因此，即使出于观察或重组的原因，改进了某些信息的存储空间或类型，明智的结构也可能保持不变。
Logical Independence:
Also the exterior structure may remain the same for most changes of the sensible structure. This is especially suitable as in this case the software does not need to be altered or fresh converted.
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