Systems Analysis and Design 8th Edition Chapter 9 Data Design

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 controls

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

Data Design Concepts Overview of File Processing File processing can be efficient and cost-effective in certain situations Potential problems Data redundancy Data integrity Data dependence Rigid data structure

Data Design Concepts Overview of File Processing Various types of files Master file Table file Transaction file Work file Security file History file

Data Design Concepts The Evolution from File Systems to Database Systems A database management system (DBMS) is a collection of tools, features, and interfaces that enables users to add, update, manage, access, and analyze the contents of a database The main advantage of a DBMS is that it offers timely, interactive, and flexible data access

Data Design Concepts The Evolution from File Systems to Database Systems Some Advantages Scalability Economy of scale Enterprise-wide application – database administrator (DBA) Controlled redundancy Data independence

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

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 No human intervention is required for two-way communication

DBMS Components Data Manipulation Language Schema 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

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

Web-Based Database Design Characteristics of Web-Based Design

Web-Based Database Design Internet Terminology Web browser Web page HTML (Hypertext Markup Language) Tags Web server Web site

Web-Based Database Design Internet Terminology Intranet Extranet Protocols Web-centric Clients Servers

Web-Based Database Design Connecting a Database to the Web Database must be connected to the Internet or intranet Middleware Adobe ColdFusion Data Security Well-designed systems provide security at three levels: the database itself, the Web server, and the telecommunication links that connect the components of the system

Data Design Terminology Definitions Entity Table or file Field Record

Data Design Terminology Key Fields Primary key Candidate key Foreign key Secondary key

Data Design Terminology Referential Integrity Validity checks can help avoid data input errors In a relational database, referential integrity means that a foreign key value cannot be entered in one table unless it matches an existing primary key in another table Orphan

Entity-Relationship Diagrams Drawing an ERD (Pg. 402) 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 A popular method is to represent entities as rectangles and relationships as diamond shapes

Entity-Relationship Diagrams Types of Relationships Three types of relationships can exist between entities One-to-one relationship (1:1) One-to-many relationship (1:M) Many-to-many relationship (M:N)

Entity-Relationship Diagrams Cardinality (Pg. 405) Cardinality notation Crow’s foot notation Unified Modeling Language (UML) Now that you understand database elements and their relationships, you can start designing tables

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

Normalization Repeating Groups and Unnormalized Design (Pg. 407) Often occur in manual documents prepared by users Unnormalized Enclose the repeating group of fields within a second set of parentheses

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

Normalization Second Normal Form (Pg. 410) A table design is in second normal form (2NF) if it is in 1NF and if all fields that are not part of the primary key are fully functionally dependent on the entire primary key A standard process exists for converting a table from 1NF to 2NF The objective is to break the original table into two or more new tables and reassign the fields so that each nonkey field will depend on the entire primary key in its table

Normalization Third Normal Form (Ppg. 411 - 412) 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 (transitional dependency) 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

Normalization A Normalization Example Standard notation formats?

Normalization Solve for Third Normal Form Use standard notation format Stud. Stud. Campus Major Course Course Instr Instr Instr Grade ID Name Address ID Title ID Name Location

Normalization Solve for Third Normal Form Stud. Stud. Campus Major Course Course Instr Instr Instr Grade ID Name Address ID Title ID Name Location STUDENT (STUDENT_ID, STUDENT_NAME, CAMPUS_ADDRESS, MAJOR, INSTR_ID) COURSE (COURSE_ID, COURSE_TITLE, INSTR_ID) INSTRUCTOR (INSTR_ID, INSTR_NAME, INSTR_LOCATION) GRADES (STUDENT_ID, COURSE_ID, GRADE)

Using Codes During Data Design Overview of Codes Because codes often are used to represent data, you encounter them constantly in your everyday life They save storage space and costs, reduce data transmission time, and decrease data entry time Can reduce data input errors

Using Codes During Data Design Types of Codes Sequence codes (379) Block sequence codes (MSIT3050) Alphabetic codes (MA) Significant digit codes (01610) Derivation codes (magazine subscriber code) Cipher codes (letters represent numbers) Action codes (“D” to Display)

Using Codes During Data Design Developing a Code Keep codes concise Allow for expansion Keep codes stable Make codes unique Use sortable codes

Using Codes During Data Design Developing a Code Avoid confusing codes Make codes meaningful Use a code for a single purpose Keep codes consistent

Steps in Database Design Create the initial ERD Assign all data elements to entities Create 3NF designs for all tables Verify all data dictionary entries After creating your final ERD and normalized table designs, you can transform them into a database

Database Models Relational Databases The relational model was introduced during the 1970s and became popular because it was flexible and powerful Because all the tables are linked, a user can request data that meets specific conditions New entities and attributes can be added at any time without restructuring the entire database

Database Models Object-Oriented Databases Many systems developers are using object-oriented database (OODB) design Object Management Group (OMG) Each object has a unique object identifier

Data Storage and Access Data storage and access involve strategic business tools Strategic tools for data storage and access Data warehouse – dimensions Data mart Data Mining

Data Storage and Access Logical and Physical Storage Logical storage Characters Data element or data item Logical record Physical storage Physical record or block Buffer Blocking factor

Data Storage and Access Data Coding and Storage Binary digits Bit Byte EBCDIC, ASCII, and Binary Unicode

Data Storage and Access Data Coding and Storage Storing dates Y2K Issue Most date formats now are based on the model established by the International Organization for Standardization (ISO) Absolute date

Data Control User ID Password Permissions Encryption Backup Recovery procedures Audit log files Audit fields