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Database Design Intro to Database Design Database Lifecycle Designer’s View Based on the notes by Kiduk Yang 1 Outline Database Design: Intro Database Lifecycle Planning & Analysis Database Design Implementation Maintenance Designer’s View 2 Turning Data Simple dumping of data on the storage medium provides little value. CUSTOMER id name address country pay due 100 523 800 12 High Rd., Leeds 52 Ln. Muncie, IN Box. 9, Miami, FL UK USA USA 33.75 0 12.50 J. Rodney E. Hoover M. Old PRODUCT product_id title cost sale price 123-19-20 169-15-34 354-90-33 Joy of Living Learning Judo Your Dream Home 12.50 20.00 18.25 19.25 25.00 24.25 SALE id 100 523 100 800 zone product_id quantity total price UK USMW UK USSE 123-19-20 354-90-33 169-15-34 123-19-20 2 1 1 1 38.50 24.25 25.00 19.25 3 ...into information The goal is not just storage of data, but ultimately the extraction of information to support decision making by key people and groups in the organization. Data Information (e.g. reports, tabulations, graphs) Decisions * Sales of Titles in the UK Zone - Summarized fact or information 50 Total Sales ($) * In the UK ZONE, Joy of Living had a sale of $38.50, and Learning Judo had a sale of $25. ** UK ZONE had the total sale of $63.50, USMW had $24.25, and USSE had $19.25. 40 30 20 10 0 Joy of Living Learning Judo Titles SALE by Zone** Title Joy of Living Learning Judo Your Dream Home UK 38.50 25.00 63.50 USMW 24.25 24.25 USSE 19.25 19.25 total 57.75 25.00 24.25 107.00 4 Database Design: Intro Database Carefully designed and constructed repository of facts (or hearsay) Part of an information system Information System Provides data collection, storage, and retrieval Facilitates data transformation Components include: • • • People Hardware Software • • e.g. DBMS, Applications Procedures Successful database design must reflect the information system of which the database is a part. 5 System Construction System Analysis establish the need and extent of an information system System Development design & implement the information system 6 Database Construction Planning & Analysis Database Development Design create complete, normalized, and integrated database models establish data management processes Implementation create storage structure load data into database provide for data management activities data entry/update, report generation, search 7 System vs. Database Lifecycle System Database Database Systems: Design, Implementation, & Management: Rob & Coronel 8 Database Lifecycle: Phase 1 Planning & Analysis Discover • • company objectives operations & structure Define • what they are how they function how they interact problems & constraints Define Database System specifications • • • database objectives database scope database boundaries Database Systems: Design, Implementation, & Management: Rob & Coronel 9 Database Lifecycle: Planning & Analysis 1. Analyze company situation • • • • what is organization’s general operating environment & its mission? what are operational components, how do they function & interact? design must satisfy the operational demands created by the organization’s mission what is organization’s structure? who controls what and who reports to whom? design involves defining information flows, queries, reports, etc. 10 Database Lifecycle: Planning & Analysis Define problems & constraints 2. • what are the problems to be solved? what are the constraints that limit the database design? e.g. time, budget, personnel, etc. Define objectives 3. database should be designed to help solve the major problems. • examine the problem space for possible database solutions. Define scope and boundaries 4. consider factors that force the design into a specific mold scope defines the extent of design. • data structures, type & number of entities, size of database boundaries • imposed by constraint, existing hardware/software 11 Database Lifecycle: Phase 2 Database Design Create a database model to support company operations and objectives to meet system requirements to meet user requirements Focus on data requirements Two Views of Data data structure data access data to information transformation Sub-phases Create conceptual design Create logical design Create physical design Database Systems: Design, Implementation, & Management: Rob & Coronel 12 DB Design: Conceptual Design Create a conceptual model i.e. abstract data structure that represent real-world items. need to understand how business works and what role data plays software and hardware independent Minimal Data Rule: “All that is needed is there, and all that is there is needed.” make sure that all data needed are in the model, and that all data in the model are needed. Conceptual Design Steps Data analysis and requirements E-R modeling and normalization Data model verification 13 Conceptual Design: Data Analysis & Requirements Discover the data that can be transformed into desired information information need what kind of information is needed? what output (queries & reports) must be generated by the system? user characteristics who will use the information? how will information be used? 14 Conceptual Design: Data Analysis & Requirements Discover the data that can be transformed into desired information ... information source where is the information to be found? how is the information to be extracted? information creation what data elements are needed to produce the information? what are the data attributes and relationships? what data transformations are to be used to produce the information? 15 Conceptual Design: Data Analysis & Requirements Develop a thorough understanding of the company’s data flow, uses, characteristics Data sources automated entry manual entry interviews, direct observation business rules narrative description of policy & procedures 16 Conceptual Design: E-R Modeling E-R Modeling steps Identify, analyze, and refine the business rule. Identify entities, attributes, and relationships Construct E-R diagram create the initial E-R diagram verify the model modify the E-R diagram Normalize process for evaluating & designing good table structures reduce data redundancies help eliminate data anomalies Repeat the last 2 steps as necessary 17 Conceptual Design: E-R model is verified against proposed system processes. E-R Model Verification confirm that intended processes can be supported by the database model careful reevaluation of the entities and detailed examination of attributes May reveal additional entity and attribute details. Verification process is iterative. Database Systems: Design, Implementation, & Management: Rob & Coronel 18 DB Design: Logical & Physical Design Logical Design specify system processes and I/O. • translate conceptual design into internal model that maps objects in model to specific DBMS constructs • detailed & functional descriptions of system components from software independent to software dependent Physical Design select the data storage and data access characteristics of the database • can affect the database performance • more important in older hierarchical and network models e.g. storage media, buffer size, etc. designers favor software that hides physical details 19 DB Design: DBMS Selection What are the advantages & disadvantages? Cost • purchase, maintenance, operational, training, etc. Features & Tools • ease-of-use, performance, DB administration, etc. • application development tools DB model • hierarchical, RDB, Object-oriented, etc. Portability • platform, O/S, SQL Hardware requirement • processor, RAM 20 Database Lifecycle: Phase 3 Implementation Create the database • • tables, forms, queries, reports programming: SQL, VBA Fine-tune • repeated testing, debugging and evaluation 21 Database Lifecycle: Phase 4 Maintenance Preventative maintenance • • Corrective maintenance • • to prevent and prepare for problem situations e.g. backup to address database system error e.g. recovery Adaptive maintenance • • to adapt to the external changes e.g. database update, enhancement 22 DB Lifecycle: Designer’s Perspective Planning Maintenanc e Analysis Design is a never-ending process... Implementation conceptual design 23 DB Design: Step 1. Planning Business Plan or Org. Goals Information Needs Database Plan Database Development Projects Strategic Planning Objectives: Understand the business model Organizational goal Product and information flow Assess the information need Put together an initial database plan Activities: Take stock of what is in place Interacts with users at all levels end-user, managers, support staff 24 Product & Info Flow in Organization DB designer must establish the product & information flow in the organization. Business Office: Book Purchasing & Inventory Management Store Warehouse Customers Publishers Barney & Nimble Inc. 25 Product & Info Flow in Organization Product & Information flow varies from organization to organization. Warehouse and inventory can use information about orders going out to publishers. Online department needs to have information on inventory. Online department can also use information about pending orders. Book Purchasing & Collection Management Warehouse Maintenance & Inventory Online Presence & Sales Publishers & Distribution Centers Fulfillment Customers Amazing.com (distributed approach) 26 Centralized Information Flow Periodic Management Report Amazing Sales & Acquisition Group invoice & other data queries electronic payments Publishers shipping info record screens inventory update Consumers Warehouse 27 DB Design: Step 2. Analysis Requirement Analysis Examination of existing database environment • • • From Information Need to Database Requirement • • • What hardware and software are available? What files/records are in use? What is under development? What type of information is desired? What can database system do to satisfy the information need? Why design it? What would it improve? Feasibility Analysis • • • Technological Operational Economical 28 DB Design: Feasibility Analysis Technological Feasibility What hardware, software, and additional resources would be needed? What is available in-house? What has to be purchased? How will the new system be integrated? 29 DB Design: Feasibility Analysis Operational Feasibility Who will design the system? Who will maintain the system? Who will do training or help-desk support? Can the available personnel provide the time? New personnel necessary? 30 DB Design: Feasibility Analysis Economic Feasibility Expected cost of the overall project? • • Other costs • • Milestones, staff-time, software, and hardware Hidden cost (unforeseen) What is the competition/comparable unit doing? Would data sharing among departments lead to additional expenses? Benefits • How soon expected? 31 DB Design: Step 3. Design Conceptual Design Map organizational & user needs to a conceptual model Data Modeling • Event Table • list of events that will occur within the database system Use Cases • Relational tables, attributes, & constraints description of how users will interact with the system User interfaces Conceptual Data Model E-R modeling Relational Data Model Relational DBMS Schema & Normalization 32 Data Modeling What is Data Modeling? Why Model? A model is a representation of reality that retains only carefully selected essential details. Logical organization of data for optimum information extraction and data manipulation To understand and identify essential data elements To produce a representation that can be transformed into a schema How? Data modeling involves • identifying entities, attributes, and relationships 33