Database design concept


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Database design concept

  1. 1. Database Design Conceptual database design Shashwat Shriparv InfinitySoft
  2. 2. Phase 2 • Involves 2 parallel activities : 1. Conceptual schema design - 2. Transaction and application design-
  3. 3. Conceptual level • It hides physical storage and concentrates on describing entities ,data types ,relationships, constraints... • Its conceptual schema describes the structure of the whole database for a community of users
  4. 4. Conceptual schema design Independent of the data base because: 1. Goal of the conceptual schema design is a complete understanding of the database structure, meaning , interrelationships, and constraints. Its best achieved independent of DBMS because each has its own rules and restrictions which can affect conceptual schema design. 2. Conceptual schema is a very valuable description of the database .Choice of DBMS and data decisions should not affect conceptual schema .
  5. 5. Conceptual schema design 3. A good understanding of the conceptual schema is crucial for the users and developers. High level data model is better than data models of individual DBMS 4. Diagrammatic representations are excellent for communicating among users, designers and analyst. since high level models use better concepts they are preferred over lower level data model.
  6. 6. Characteristics of data model 1. Expressiveness 2. Simplicity and understandability 3. Minimality (least basic concepts that are distinct and non overlapping) 4. Diagrammatic representation 5. Formality (formal unambiguous specification of data)
  7. 7. Approaches to conceptual schema design 1. Centralized approach :requirements of different applications and user groups are merged together. a single schema is designed corresponding to the merged set of requirements. Task is arduous and time consuming . DBA and staff accomplish the task.
  8. 8. Approaches to conceptual schema design 2. View integration approach : a schema is designed for each user group based only on its requirements .we develop a high level schema for each group and combine into a GLOBAL CONCEPTUAL SCHEMA. Again DBA and staff accomplish the task.
  9. 9. Strategies for schema design 1. Top down strategy :start a schema containing high level abstractions and then apply successive top – down refinement. 2. Bottom up strategy :start a schema containing basic abstractions and then combine or add these abstractions .
  10. 10. Strategies for schema design 3. Inside out strategy : special case of bottom up where attention is focused on a central set of concepts that are most evident. Modeling then spreads outwards by considering new concepts in the vicinity of existing ones . 4. Mixed strategy :requirements partitioned according to T D and part of schema designed according to B U.
  11. 11. Course offering Course # Sec # semester instructor course instructorOffered by name Course# Sec# semester (1,N)(1,1)
  12. 12. faculty student faculty student advises Committee chair of
  13. 13. Shashwat Shriparv InfinitySoft