Question

Describe the three-schema architecture. Why do we need mappings among schema levels?

Answer 1

Answer-

Three-schema architecture-

1. internal schema
2. conceptual schema
3. External schema

1. Internal schema-

• It has internal stage to identify physical storage device knowledges and retrieve paths and typically applies a physical information model.

2. conceptual schema

• It has conceptual stage to identify the structure and constraints for the conception database for a gathering of users and consumes a conceptual an enforcement data model.

External schema

• It has external level to inform the different user surveys usually practices the same data point model as the conceptual schema.

Need mappings among schema levels-

• It is call for to transform requests and data
• They are mapped by the DATABASE MANAGEMENT SYSTEM to the internal schema for implementation.
• Data obtained from the internal DATABASE MANAGEMENT SYSTEM stage is reformatted to supply the user external view.
  

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