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DATABASE DESIGN (DBLC (The Database Initial Study (•Overall purpose:
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DATABASE DESIGN
DBLC
- The Database Initial Study
•Overall purpose:
–Analyze company situation
–Define problems and constraints
–Define objectives
–Define scope and boundaries
•Interactive and iterative processes required to complete first phase of DBLC successfully
•Necessary to concentrate on data characteristics required to build database model
•Two views of data within system:
–Business view
•Data as information source
–Designer’s view
•Data structure, access, and activities required to transform data into information
- Implementation and Loading
•Actually implement all design specifications from previous phase:
–Install the DBMS
•Virtualization: creates logical representations of computing resources independent of physical resources
–Create the Database
–Load or Convert the Data
•Occurs in parallel with applications programming
•Database tools used to prototype applications
•If implementation fails to meet some of system’s evaluation criteria
•Once database has passed evaluation stage, it is considered operational
•Beginning of operational phase starts process of system evolution
•Problems not foreseen during testing surface
- Maintenance and Evolution
Required periodic maintenance:
–Preventive maintenance (backup)
–Corrective maintenance (recovery)
–Adaptive maintenance (enhancement perf.)
–Generation of database access statistics
–Periodic security audits
–Periodic system-usage summaries
SDLC
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Analysis
•Problems defined during planning phase are examined in greater detail during analysis
•Thorough audit of user requirements
•Existing hardware and software systems are studied
Detailed Systems Design
•Designer completes design of system’s processes
•Includes all necessary technical specifications
•Steps laid out for conversion from old to new system
•Training principles and methodologies are also planned
Implementation
•Hardware, DBMS software, and application programs are installed
•Cycle of coding, testing, and debugging continues until database is ready for delivery
•Database is created and system is customized
Maintenance
•Three types of maintenance activity:
–Corrective maintenance
–Adaptive maintenance
–Perfective maintenance
•Computer-aided systems engineering (CASE)
–Produce better systems within reasonable amount of time and at reasonable cost
–CASE-produced applications are structured, documented, and standardized
Logical Design Steps
- Mapping the Conceptual Model to the Relational Model
- Validate Logical Model using Normalization
- Validate Logical Model Integrity Constraints
- Validate the Logical Model against User Requirements
Conceptual Design
- Data Analysis and Requirements
•Discover data element characteristics
–Obtains characteristics from different sources
•Requires thorough understanding of the company’s data types and their extent and uses
•Take into account business rules
–Derived from description of operations
- Entity Relationship Modeling and Normalization
•Designer enforces standards in design documentation
–Use of diagrams and symbols, documentation writing style, layout, other conventions
•Business rules must be incorporated into conceptual model
•ER model is a communications tool as well as design blueprint
•Verified against proposed system processes
•Revision of original design
–Careful reevaluation of entities
–Detailed examination of attributes describing entities
•Define design’s major components as modules:
–Module: information system component that handles specific function
- Distributed Database Design
•Portions of database may reside in different physical locations
–Database fragment: subset of a database stored at a given location
•Processes accessing the database vary from one location to another
•Designer must also develop data distribution and allocation strategies
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Physical Design Steps
- Define Data Storage Organization
- Define Integrity and Security Measures
- Determine Performance Measures