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Chapter 7

Chapter 7. PHASE 3: SYSTEMS DESIGN. Data Design. Chapter Objectives. Explain data design concepts and data structures Describe file processing systems and various types of files Understand database systems and define the components of a database management system (DBMS)

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Chapter 7

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  1. Chapter 7 PHASE 3: SYSTEMS DESIGN Data Design

  2. Chapter Objectives • Explain data design concepts and data structures • Describe file processing systems and various types of files • Understand database systems and define the components of a database management system (DBMS) • Describe Web-based data design

  3. Chapter Objectives • Explain data design terminology, including entities, fields, common fields, records, files, tables, and key fields • Describe data relationships, draw an entity-relationship diagram, define cardinality, and use cardinality notation • Explain the concept of normalization • Explain the importance of codes and describe various coding schemes

  4. Chapter Objectives • Describe relational and object-oriented database models • Explain data warehousing and data mining • Differentiate between logical and physical storage and records • Explain data control measures

  5. Introduction • You will develop a physical plan for data organization, storage, and retrieval • Begins with a review of data design concepts and terminology, then discusses file-based systems and database systems, including Web-based databases • Concludes with a discussion of data storage and access, including strategic tools such as data warehousing and data mining, physical design issues, logical and physical records, data storage formats, and data control

  6. Data Design Concepts • Data Structures • A file or table contains data about people, places, things, or events that interact with the system • File-oriented system • File processing system • Database system

  7. Data Design Concepts • Overview of File Processing • Potential problems • Data redundancy • Data integrity • Rigid data structure

  8. Data Design Concepts • Overview of File Processing • Uses various types of files • Master file • Table file • Transaction file • Work file – scratch file • Security file • History file

  9. Data Design Concepts • Overview of Database Systems • A properly designed database system offers a solution to the problems of file processing • Provides an overall framework that avoids data redundancy and supports a real-time, dynamic environment • Database management system (DBMS) • The main advantage of a DBMS is that it offers timely, interactive, and flexible data access

  10. Data Design Concepts • Overview of Database Systems • Advantages • Scalability • Better support for client/server systems • Economy of scale • Flexible data sharing • Enterprise-wide application – database administrator (DBA) • Stronger standards

  11. Data Design Concepts • Overview of Database Systems • Advantages • Controlled redundancy • Better security • Increased programmer productivity • Data independence

  12. Data Design Concepts • Database Tradeoffs • Because DBMSs are powerful, they require more expensive hardware, software, and data networks capable of supporting a multi-user environment • More complex than a file processing system • Procedures for security, backup, and recovery are more complicated and critical

  13. DBMS Components • Interfaces for Users, Database Administrators, and Related Systems • Users • Query language • Query by example (QBE) • SQL (structured query language) • Database Administrators • A DBA is responsible for DBMS management and support

  14. DBMS Components • Interfaces for Users, Database Administrators, and Related Systems • Related information systems • A DBMS can support several related information systems that provide input to, and require specific data from, the DBMS

  15. DBMS Components • Data Manipulation Language • A data manipulation language (DML) controls database operations, including storing, retrieving, updating, and deleting data • Schema • The complete definition of a database, including descriptions of all fields, tables, and relationships, is called a schema • You also can define one or more subschemas

  16. DBMS Components • Physical Data Repository • The data dictionary is transformed into a physical data repository, which also contains the schema and subschemas • The physical repository might be centralized, or distributed at several locations • ODBC – open database connectivity • JDBC – Java database connectivity

  17. Web-Based Database Design • Characteristics of Web-Based Design • In a Web-based design, the Internet serves as the front end, or interface, for the database management system • Internet technology provides enormous power and flexibility • Web-based systems are popular because they offer ease of access, cost-effectiveness, and worldwide connectivity

  18. Web-Based Database Design • Connecting a Database to the Web • Database must be connected to the Internet or intranet • Middleware • Macromedia’s ColdFusion

  19. Web-Based Database Design • Data Security • Web-based data must be totally secure, yet easily accessible to authorized users • To achieve this goal, well-designed systems provide security at three levels: • The database itself • The Web server • The telecommunication links that connect the components of the system

  20. Data Design Terminology • Definitions • Entity • Table or file • Field • Attribute • Common field • Record • Tuple

  21. Data Design Terminology Key Fields • Primary key • Composite key • (aka Combination key , Concatenated key, Multi-valued key) • Candidate key • Nonkey field • Foreign key • Secondary key

  22. Data Design Terminology • Referential Integrity • Validity checks can help avoid data input errors

  23. Entity-Relationship Diagrams • An entity is a person, place, thing, or event for which data is collected and maintained • Provides an overall view of the system, and a blueprint for creating the physical data structures • Entity-relationship diagram

  24. Entity-Relationship Diagrams • Drawing an ERD • The first step is to list the entities that you identified during the fact-finding process and to consider the nature of the relationships that link them

  25. Entity-Relationship Diagrams • Types of Relationships • One-to-one relationship (1:1) • One-to-many relationship (1:M) • Many-to-many relationship (M:N) • Associative entity

  26. Entity-Relationship Diagrams • Cardinality • Cardinality notation • Crow’s foot notation

  27. Normalization • Table design • Involves four stages: unnormalized design, first normal form, second normal form, and third normal form • Most business-related databases must be designed in third normal form

  28. Normalization • Standard Notation Format • Designing tables is easier if you use a standard notation formatto show a table’s structure, fields, and primary key Example: NAME (FIELD 1, FIELD 2, FIELD 3)

  29. Normalization • Repeating Groups and Unnormalized Designs • Repeating group • Often occur in manual documents prepared by users • Unnormalized design

  30. Normalization • First Normal Form • A table is in first normal form (1NF) if it does not contain a repeating group • To convert, you must expand the table’s primary key to include the primary key of the repeating group • Second Normal Form • To understand second normal form (2NF), you must understand the concept of functional dependence • Functionally dependent

  31. Normalization • Second Normal Form • A standard process exists for converting a table from 1NF to 2NF • Create and name a separate table for each field in the existing primary key • Create a new table for each possible combination of the original primary key fields • Study the three tables and place each field with its appropriate primary key

  32. Normalization • Second Normal Form • Four kinds of problems are found with 1NF designs that do not exist in 2NF • Consider the work necessary to change a particular product’s description • 1NF tables can contain inconsistent data • Adding a new product is a problem • Deleting a product is a problem

  33. Normalization • Third Normal Form • 3NF design avoids redundancy and data integrity problems that still can exist in 2NF designs • A table design is in third normal form (3NF) if it is in 2NF and if no nonkey field is dependent on another nonkey field • To convert the table to 3NF, you must remove all fields from the 2NF table that depend on another nonkey field and place them in a new table that uses the nonkey field as a primary key

  34. Normalization A Normalization Example • To show the normalization process, consider the familiar situation, which depicts several entities in a school advising system: ADVISOR, COURSE, and STUDENT

  35. Steps in Database Design • Create the initial ERD • Assign all data elements to entities • Create 3NF designs for all tables, taking care to identify all primary, secondary, and foreign keys • Verify all data dictionary entries • After creating your final ERD and normalized table designs, you can transform them into a database

  36. Chapter Summary • Files and tables contain data about people, places, things, or events that affect the information system • DBMS designs are more powerful and flexible than traditional file-oriented systems • Data design tasks include creating an initial ERD; assigning data elements to an entity; normalizing all table designs; and completing the data dictionary entries for files, records, and data elements Any questions?

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