DBST 651 DBST 651 Session 2 part 4 of 4 McGraw Hill Irwin Copyright 2007 by The McGraw Hill Companies Inc All rights reserved Chapter 2 Introduction to Database Development McGraw Hill Irwin Copyright 2007 by The McGraw Hill Companies Inc All rights reserved DBST 651 Chap 2 provides a good overview of the development process 2 3 Outline Context for database development Goals of database development Phases of database development CASE tools 2 4 Information System INPUTS Loan Applications ENVIRONMENT Payments OUTPUTS PROCESSES Student Loan Processing System Delinquency Notices ENVIRONMENT Statements Cash Disbursements Status Changes DATABASE 2 5 Traditional Life Cycle Preliminary Investigation Problem Statement Feasibility Study Systems Analysis Feedback System Requirements Systems Design Feedback Design Specifications Systems Implementation Feedback Operational System Maintenance 2 6 Development Alternatives Difficulties Operational system is produced late Rush to begin implementation Requirements are difficult to capture Alternative methodologies Spiral approaches Rapid application development Prototypes may reduce risk 2 7 Graphical Models Explicit or implicit Data model Process model Environment interaction model Emphasize data model 2 8 Broad Goals of Database Development Develop a common vocabulary Define data meaning Ensure data quality Provide efficient implementation 2 9 Develop a Common Vocabulary Diverse groups of users Difficult to obtain acceptance of a common vocabulary Compromise to find least objectionable solution Unify organization by establishing a common vocabulary 2 10 Define Meaning of Data Business rules support organizational policies Restrictiveness of business rules Too restrictive reject valid business interactions Too loose allow erroneous business interactions Exceptions allow flexibility 2 11 Data Quality Poor data quality leads to poor decision making Difficult customer communication Inventory shortages Cost benefit tradeoff to achieve desired level of data quality Long term effects of poor data quality 2 12 Data Quality Measures Completeness Lack of ambiguity Timeliness Correctness Consistency Reliability 2 13 Efficient Implementation Supersedes other goals Optimization problem Maximize performance Subject to constraints of data quality data meaning and resource usage Difficult problem Number of choices Relationships among choices DBMS specific 2 14 Database Development Phases Data requirements Conceptual Data Modeling ERD Logical Database Design Tables Distributed Database Design Distribution Schema Physical Database Design Internal Schema Populated DB 2 15 Conceptual Data Modeling Information content of the database Entity relationship diagram ERD showing entity types and relationships Historically DBMSs did not support many constraints Diverse formats for database requirements 2 16 Logical Database Design Refine conceptual design Convert ERD to table design Analyze design for excessive redundancies Normalization tool to reason about redundancies Add constraints to enforce business rules 2 17 Distributed Database Design Location of data and processing Performance orientation not information content orientation Allocate subsets of database to different sites Replicate subsets of database to improve availability 2 18 Physical Database Design Performed at each independent database site Minimize response time without consuming excessive resources Tradeoffs retrieval versus update Flexible designs versus specialized designs Decisions indexes data placement 2 19 Splitting Conceptual Design Conceptual Data Modeling Data Requirements View Design View ERDs View Integration Entity Relationship Diagrams 2 20 Cross Checking Requirements System Requirements Data Requirements Database Development ERDs Table Design Application Requirements Cross Checking Application Development Process Models Interaction Models Prototypes Operational Applications Operational Database Operational System 2 21 Design Skills Soft Qualitative Degree of subjectivity People oriented Hard Quantitative Objective Intensive data analysis 2 22 Design Skills in Phases Data Requirements Conceptual Data Modeling Design Skills Soft Entity Relationship Diagrams Logical Database Design Relational Database Tables Distributed Database Design Distribution Schema Physical Database Design Internal Schema Populated Database Hard 2 23 Features of CASE Tools Diagramming Documentation Analysis Prototyping 2 24 Classification of CASE Tools Front end vs Back end Front end emphasize data modeling and logical analysis Back end emphasize code generation and physical design DBMS dependent vs DBMS independent 2 25 Commercial CASE Tools PowerDesigner 10 Oracle Designer 10g Visual Studio Net Enterprise Architect ERWin Data Modeler ER Studio Visible Analyst 2 26 ER Assistant CASE tool distributed with the textbook Customized for this textbook supports the ERD notation used in Chapters 5 and 6 Drawing tool Diagram checking Easy to use and powerful tool 2 27 Visio Professional Entry level version of Visual Studio Net Enterprise Architect Drawing tools Stencils for database diagrams Glue feature to retain connections Data dictionary support Analysis tools Diagram layout Reverse engineering 2 28 Summary Background for Chapters 5 to 8 Relationship to information systems development Broad goals Development phases CASE tool features 2 29 DBST 651 Do chapter 1 in the workbook on nova or your PC Install ER Assistant if you haven t yet Readings 2 30