Database Systems: Design, Implementation, and Management Chapter 9 Database Design The Systems Development Life Cycle (SDLC) • Traces history (life cycle) of information system • Database design and application development mapped out and evaluated • Iterative rather than sequential process 2 JMSB BTM and the SDLC Entire SDLC BTM Minor 3 Technology Acceptance Model http://www.istheory.yorku.ca/Technologyacceptancemodel.htm Davis, F. D. (1989). Perceived usefulness, perceived ease of use, and user acceptance of information technology. MIS Quarterly, 13(3), 319-339. Two fundamental issues in deciding how much functionality to implement in a new system • How much functionality should you implement? (Perceived Usefulness) 1. Baseline replication: The new system must at least be as functional as the old one 2. User-requested functionality: The system should add new features required by users 3. Analyst-suggested functionality: The system may optionally go beyond users’ expectations • How much retraining effort would it take users to learn to use the new system? (Perceived Ease of Use) 1. Baseline replication: Minimal effort, or net zero effort (takes no more effort than time and effort saved from switching from old system) 2. User-requested functionality: Users must feel that new retraining is worthwhile considering the benefits they have asked for 3. Analyst-suggested functionality: No extra retraining should be required, unless users are absolutely convinced of benefits of extended functionality 5 The Database Life Cycle (DBLC) • Six phases: – Database initial study – Database design – Implementation and loading – Testing and evaluation – Operation – Maintenance and evolution 6 Conceptual Design • Creating a detailed, validated ERD • Independent of RDBMS chosen DBMS Software Selection • Critical to information system’s smooth operation • Common factors affecting purchasing decisions: – – – – – Cost DBMS features and tools Underlying model Portability DBMS hardware requirements • http://en.wikipedia.org/wiki/Comparison_of_re lational_database_management_systems 8 Logical Design • Specifying the tables, attributes and keys • Specifying the domain integrity and attribute constraints • Dependent on chosen RDBMS Physical Design • Dependent on chosen hardware Top-down versus bottom-up database design strategies • Top-down design – Identifies groups of entities – Defines data elements for each of those groups • Definition of different entity types • Definition of each entity’s attributes • Bottom-up design – Identifies data attributes (items) – Groups them together into entities, and then larger groups 11 Centralized vs. decentralized design • Centralized design – When data component is composed of small number of objects and procedures – Typical of small systems • Decentralized design – Data component has large number of entities – Complex relations on which complex operations are performed – Problem is spread across several operational sites 12 Sources • Most of the slides are adapted from Database Systems: Design, Implementation and Management by Carlos Coronel and Steven Morris. 11th edition (2015) published by Cengage Learning. ISBN 13: 978-1-285-19614-5 • Other sources are noted on the slides themselves 13