Information System provides data collection, storage, and retrieval Facilitates data transformation Includes people, procedures, hardware, and software 3 The Information System (Count. ) System Analysis Establishes need and extent of an Information system Refer to Recommended Requirements Gathering Practices we are NOT DOING A SYSTEM REST ANALYSIS Systems development Process of creating Information system Database development Creation of database models Implementation Creating storage structure Loading data into database Providing for data management 4 Systems Development Life Cycle
Database Lifestyle (ODBC) 5 Database Life Cycle (ODBC) Phase 1 Phase 2 Phase 3 Phase 4 Phase 5 Phase 6 6 Organization Phase 1: Database Initial Study Purposes Analyze company situation Operating environment Organizational structure Define problems and constraints Define objectives Define scope and boundaries 7 Initial Study Activities 8 Phase 2: Database Design Most Critical ODBC phase Makes sure final product meets requirements Focus on data requirements Subleases l. Create conceptual design II. DB’S software selection Ill. Create logical design IV. Create physical design 9 Two Views of Data 10 .
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Conceptual Design Data modeling creates abstract data structure to represent real-world items High level of abstraction Four steps Data analysis and requirements *Entity relationship modeling and normalization* 11 Data analysis and Requirements Focus on: Information needs Information users Information sources Data sources Developing and gathering end-user data views Direct observation of current system Interfacing with systems design group Business rules 12 Entity Relationship Modeling and Normalization 13 E-R Modeling is Iterative 14 Concept Design: Tools and Sources 15 Data Model Verification
E-R model is verified against proposed system processes End user views and required transactions Access paths, security, concurrency control Business-imposed data requirements and constraints Reveals additional entity and attribute details 16 E-R Model Verification Process Iterative Process of Verification 18 II. DB’S Software Selection DB’S software selection is critical Advantages and disadvantages need study Factors affecting purchasing decision Cost DB’S features and tools Underlying model Portability DB’S hardware requirements 19 Ill. Logical Design Translates conceptual design into internal model
Maps objects in model to specific DB’S constructs Design components Tables Indexes Views Transactions Access authorities Others 20 IV. Physical Design Selection of data storage and access characteristics Very technical More important in older hierarchical and network models Becomes more complex for distributed systems Designers favor software that hides physical details 21 Creation of special storage-related constructs to house end-user tables Data loaded into tables Other issues Performance Security Backup and recovery Integrity Company standards Concurrency controls Phase 4: Testing and Evaluation
Database is tested and fine-tuned for performance, integrity, concurrent access, and security constraints Done in parallel with application programming Actions taken if tests fail Fine-tuning based on reference manuals Modification of physical design Modification of logical design Upgrade or change DB’S software or hardware Phase 5: Operation Database considered operational Unforeseen problems may surface Demand for change is constant 24 Phase 6: Maintenance and Evaluation Preventative maintenance Corrective maintenance Adaptive maintenance Assignment of access permissions Generation of database access statistics to monitor performance Periodic security audits based on system-generated statistics.