IST 210 Database Design Process Mam Saira

IST 210 2

IST 210 n n Key points Database design must reflect the information system of which the database is a part Information systems undergo evaluation and revision within a framework known as the Systems Development Life Cycle (SDLC) Databases also undergo evaluation and revision within a framework known as the Database Life Cycle (DBLC) There are two general design strategies exist: n n top-down vs. bottom-up design centralized vs. decentralized design 3

References IST 210 n n n STANDISH GROUP (1995): The CHAOS Report into Project Failure, The Standish Group International Inc. STANDISH GROUP (1996): Unfinished Voyages, The Standish Group International Inc. Croswell, P. , 1991. "Obstacles to GIS implementation and guidelines to increase the opportunity for success, " Journal of the Urban and Regional Information Systems Association, 3(1): 43 -56. 4

IST 210 Lessons from Business Automation n Era of finance and operations: ’ 60 s - ’ 70 s n n Manufacturing software: ’ 70 s - ’ 80 s n n Business accounting systems Separate applications for inventory, ordering, forecasting, shop floor operations, logistics, etc. Era of the business enterprise: ’ 90 s - ’ 00 s n n Separate applications get rolled into “enterprise resource planning” system Sales force automation, customer service center, campaign management, automated email response, etc. get rolled into “customer relationship management. ” 5

IST 210 Successful automation requires an interlocking of the: User (Someone doing “real work” ) Infrastructure (Computer and Human) Management (Organization) 6

IST 210 American Airlines settled a lawsuit with Budget Rent-A-Car, Marriott Corp. and Hilton Hotels after the $165 million CONFIRM car rental and hotel reservation system project collapsed into chaos. 7

IST 210 n 84% of all automation projects have significant or major problems STANDISH GROUP (1995): The CHAOS Report into Project Failure, The 8 Standish Group International Inc.

IST 210 Percent Over Budget n 53% of all automation projects are more than 50% over budget n 23% of all automation projects are more than 100% over budget STANDISH GROUP (1995): The CHAOS Report into Project Failure, The Standish Group International Inc. 9

IST 210 n Percent of Time Under Estimated 49% of all automation projects take twice as long to complete as planned STANDISH GROUP (1995): The CHAOS Report into Project Failure, The 10 Standish Group International Inc.

IST 210 Percent Planned Functionality n 54% of all automation projects deliver less than half of the promised functionality STANDISH GROUP (1995): The CHAOS Report into Project Failure, The 11 Standish Group International Inc.

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IST 210 n n n n Most problems are non-technical Poorly selected data Badly organized data Incorrect data models Software has limited capability (oversell) Systems managers underestimate time requirements Systems can be underutilized Systems can be (and have been) abandoned Personnel problems 13

IST 210 Changing Data into Information n Data n n n Raw facts stored in databases Need additional processing to become useful Information n Required by decision maker Data processed and presented in a meaningful form Transformation 14

IST 210 The Information System n Database n n n Carefully designed and constructed repository of facts Part of an information system Information System n n n Provides data collection, storage, and retrieval Facilitates data transformation Includes people, hardware, and software n Software: Database(s), Application programs, and Procedures 15

IST 210 The Information System (Con’t. ) n System Analysis n Establishes need and extent of an information system n n n We are NOT DOING A SYSTEM REQ’T ANALYSIS!! Systems development n n Refer to Recommended Requirements Gathering Practices Process of creating information system Database development n n n Process of database design and implementation Creation of database models Implementation n Creating storage structure Loading data into database Providing for data management 16

IST 210 Systems Development Life Cycle System Analysis Database Organization (IST 210) 17

IST 210 Database Lifecycle (DBLC) Phase 1 Phase 2 Phase 3 Phase 4 Database Organization (IST 210) Phase 5 Phase 6 18

IST 210 Phase 1: Database Initial Study n Purposes n Analyze company situation n n Operating environment Organizational structure Define problems and constraints Define objectives Define scope and boundaries 19

IST 210 Initial Study Activities 20

IST 210 Phase 2: Database Design n n Most Critical DBLC phase Makes sure final product meets requirements Focus on data requirements Subphases n n I. Create conceptual design II. DBMS software selection III. Create logical design IV. Create physical design 21

IST 210 Two Views of Data 22

IST 210 I. Conceptual Design n Data modeling creates abstract data structure to represent real-world items High level of abstraction Four steps n n n Data analysis and requirements *Entity relationship modeling and normalization* *Data model verification* 23

IST 210 Data analysis and Requirements n Focus on: n n Data sources n n Information needs Information users Information sources Developing and gathering end-user data views Direct observation of current system Interfacing with systems design group Business rules 24

IST 210 Entity Relationship Modeling and Normalization 25

IST 210 E-R Modeling is Iterative 26

IST 210 Concept Design: Tools and Sources 27

IST 210 n Data Model Verification E-R model is verified against proposed system processes n n End user views and required transactions Access paths, security, concurrency control Business-imposed data requirements and constraints Reveals additional entity and attribute details 28

IST 210 E-R Model Verification Process 29

IST 210 Iterative Process of Verification 30

II. DBMS Software Selection IST 210 n n n DBMS software selection is critical Advantages and disadvantages need study Factors affecting purchasing decision n n Cost DBMS features and tools Underlying model Portability DBMS hardware requirements 31

IST 210 III. Logical Design n Translates conceptual design into internal model Maps objects in model to specific DBMS constructs Design components n n n Tables Indexes Views Transactions Access authorities Others 32

IST 210 n IV. Physical Design Selection of data storage and access characteristics n n Very technical More important in older hierarchical and network models Becomes more complex for distributed systems Designers favor software that hides physical details 33

IST 210 Phase 3: Implementation and Loading n n n Creation of special storage-related constructs to house end-user tables Data loaded into tables Other issues n n n Performance Security Backup and recovery Integrity Company standards Concurrency controls 34

IST 210 Phase 4: Testing and Evaluation n 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 n n Fine-tuning based on reference manuals Modification of physical design Modification of logical design Upgrade or change DBMS software or hardware 35

IST 210 Phase 5: Operation n n Database considered operational Starts process of system evaluation Unforeseen problems may surface Demand for change is constant 36

IST 210 Phase 6: Maintenance and Evaluation n n n Preventative maintenance Corrective maintenance Adaptive maintenance Assignment of access permissions Generation of database access statistics to monitor performance Periodic security audits based on systemgenerated statistics Periodic system usage-summaries 37

IST 210 DB Design Strategy Notes n Top-down n 1) Identify data sets 2) Define data elements Bottom-up n n 1) Identify data elements 2) Group them into data sets 38

IST 210 Top-Down vs. Bottom-Up 39

IST 210 Centralized vs. Decentralized Design n Centralized design n Typical of simple databases Conducted by single person or small team Decentralized design n Larger numbers of entities and complex relations Spread across multiple sites Developed by teams 40

IST 210 Decentralized Design 41