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How are the internal external and conceptual schemas related to concept of logical and physical data independence?
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∙ 9y ago
The internal schema represents the physical storage structure of data, the external schema represents how different users view the data, and the conceptual schema defines the logical structure of the entire database. Logical data independence means that the conceptual schema can change without affecting the external schemas, while physical data independence means that changes in the physical storage structures do not affect the conceptual or external schemas.
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Explain the difference of internal external and conceptual schemas how are these schema layers related to the concept of logical and physical data independence?
External schemas allows data access to be customized (and authorized) at the level of individual users or groups of users. Conceptual (logical) schemas describes all the data that is actually stored in the database. While there are several views for a given database, there is exactly one conceptual schema to all users. Internal (physical) schemas summarize how the relations described in the conceptual schema are actually stored on disk (or other physical media). External schemas provide logical data independence, while conceptual schemas offer physical data independence.
Distinguish between logical data independence and physical data independence?
logical data : refer to the immunity of the external scheme towards changes in the conceptual scheme.physical data: refer to the immunity of the conceptual scheme towards changes in the internal scheme.
Mapping in DBMS architecture?
We know that three view-levels are described by means of three schemas. These schemas are stored in the data dictionary. In DBMS, each user refers only to its own external schema. Hence, the DBMS must transform a request on. a specified external schema into a request against conceptual schema, and then into a request against internal schema to store and retrieve data to and from the database. The process to convert a request (from external level) and the result between view levels is called mapping. The mapping defines the correspondence between three view levels. The mapping description is also stored in data dictionary. The DBMS is responsible for mapping between these three types of schemas. There are two types of mapping. (i) External-Conceptual mapping (ii) Conceptual-Internal mapping External-Conceptual Mapping An external-conceptual mapping defines the correspondence between a particular external view and the conceptual view. The external-conceptual mapping tells the DBMS which objects on the conceptual level correspond to the objects requested on a particular user's external view. If changes are made to either an external view or conceptual view, then mapping must be changed accordingly. Conceptual-Internal Mapping The conceptual-internal mapping defines the correspondence between the conceptual view and the internal view, i.e. database stored on the physical storage device. It describes how conceptual records are stored and retrieved to and from the storage device. This means that conceptual-internal mapping tells the DBMS that how the conceptual! records are physically represented. If the structure of the stored database is changed, then the mapping must be changed accordingly. It is the responsibility of DBA to manage such changes.
What is the difference between logical and physical data independence?
The logical data independence is the ability to modify a logical schema without making external view or application program change. The physical data independence is the ability to modify a physical schema without making external view or application prrogram change.
2.5 What is the difference between logical data independence and physical data independence?
Logical data independence refers to the ability to change the conceptual schema without affecting the external schema or application programs. Physical data independence, on the other hand, refers to the ability to change the physical schema without affecting the conceptual schema. This allows changes in the storage structure or access methods without changing how data is viewed or accessed by applications.
What Logical data independence and physical data independence?
Logical Data Independence : The ability to change the logical schema without changing the external schema or application programs is called as Logical Data Independence.Physical Data Independence : The ability to change the physical schema without changing the logical schema is called as Physical Data Independence.Logical Data Independence :being able to maintain change at external layer without having to make any change at the concept.Physical Data Independence : we want to be able to make any change on the conceptual level to deal without any change at the physical
What is an adjustment to internal and external physical structures?
Internal and external? 4real
Why logical data independence is more difficult than physical data independence?
Logical data independence is considered more difficult than physical data independence because it involves changes to the conceptual schema and external schema, which are more closely tied to the way data is organized and viewed in the application. Physical data independence, on the other hand, deals with changes to the internal schema, which is more abstract and can be modified with less impact on the overall system.
What is dbms architecture?
1. External view : this is a highest level of abstraction as seen by user. This level of abstraction describes only the part of entry database. It is based on the conceptual model, is the end user view of data environment. Each external view described by means of a schema called an external schema or subschema. The external schema consists of the definition of the logical records and the relationships in the external view. The external schema also contains he method of deriving the objects in the external view from the objects in the conceptual view. The object include entities, attributes and relationships.2. Conceptual level : at this level of database abstraction all the database entities and the relationships among them are included. One conceptual view represents the entire database. the conceptual schema defines ths conceptual view. It there is only one conceptual schema per database. This schema also contains the method deriving from the objects in the conceptual view from the objects in the internal view.. at this level a database is described logically rather then physically in term of data structure.3. Internal(physical) level : this lowest level of abstraction. it closest to physical storage device. It describes how data are actually stored on the storage medium. The internal schema, which contains the definition of the stored record, the method representing the data fields, expresses the internal view and the access aids used.
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How it is related to data independence?
Hi, Data Independence refers to the immunity of user application to make changes in the definition and organization of Data. There are three types of Data Independence - 1. Logical Data Independence - The ability to change the logical (conceptual) schema without changing the External schema (User View) is called logical data independence. 2. Physical Data Independence - The ability to change the physical schema without changing the logical schema is called physical data independence. 3. View Data Independence - always independent,no effect.
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