Data independence

(′dad·ə in·də′pen·dəns)

(computer science) Separation of data from processing, either so that changes in the size or format of the data elements require no change in the computer programs processing them or so that these changes can be made automatically by the database management system.

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Computer Desktop Encyclopedia: data independence

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Techniques that allow data to be changed without affecting the applications that process it. There are two kinds of data independence. The first type is data independence for data, which is accomplished in a database management system (DBMS). It allows the database to be structurally changed without affecting most existing programs. Programs access data in a DBMS by field and are concerned with only the data fields they use, not the format of the complete record. Thus, when the record layout is updated (fields added, deleted or changed in size), the only programs that must be changed are those that use those new fields.

Data Independence for Processing

The second type of data independence relates to processing and refers to miscellaneous data used in programs that might change in the future, such as discount rates, product descriptions and error messages. Such data should be stored in a database and not "hard wired" into the code of the program. When values change, only the database item is altered, a much simpler task than recompiling numerous programs.

Data Independence for Data

Program #1 reserves space for the entire record (fields A to K). If the record format is changed, the space must be changed. Program #2 calls the DBMS to deliver just the fields it uses (D G H K). It still reserves space, but unless a field has been resized, it is not affected by other field changes. Program #3 is fully independent of the data structure. It calls for data by field name, and the DBMS allocates the space at runtime.

Data Independence for Processing

Program #1 uses a hard-coded value to test credit limit. To change the limit, the program must be recompiled. Program #2 retrieves the credit limit from a database. To change it, only the database must be updated, a simpler task.

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Wikipedia: Data independence

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This article may require cleanup to meet Wikipedia's quality standards. Please improve this article if you can. (January 2008)

Data independence is the type of data transparency that matters for a centralized DBMS. It refers to the immunity of user applications to make changes in the definition and organization of data.

Physical data independence deals with hiding the details of the storage structure from user applications. The application should not be involved with these issues, since there is no difference in the operation carried out against the data.

The data independence and operation independence together gives the feature of data abstraction. There are two levels of data independence.

1 First level
2 Second level
3 Data Independence Types
4 See also

First level

The logical structure of the data is known as the schema definition. In general, if a user application operates on a subset of the attributes of a relation, it should not be affected later when new attributes are added to the same relation. Logical data independence indicates that the conceptual schema can be changed without affecting the existing schemas.

It has two types

1.PONKA 2.MONKA

Second level

The physical structure of the data is referred to as "physical data description". Physical data independence deals with hiding the details of the storage structure from user applications. The application should not be involved with these issues since, conceptually, there is no difference in the operations carried out against the data. There are two types of data independence:

Logical data independence: The ability to change the logical (conceptual) schema without changing the External schema is called logical data independence. For example, the addition or removal of new entities, attributes, or relationships to the conceptual schema should be possible without having to change existing external schemas or having to rewrite existing application programs.
Physical data independence: The ability to change the physical schema without changing the logical schema is called physical data independence. For example, a change to the internal schema, such as using different file organization or storage structures, storage devices, or indexing strategy, should be possible without having to change the conceptual or external schemas.