Download - Systems Analysis
Systems Analysis & Design 7th Edition
2008 Truman College
Chapter-08Data Design
Mohammad Moizuddin
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Safety Share
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Chapter Objectives
Explain data design concepts and data structures
Describe file processing systems
Explain database systems and define the components of a database management system (DBMS)
Describe Web-based data design
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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
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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
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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
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Data Design Concepts
Data Structures A file or table contains data about people, places or
events that interact with the system File-oriented system File processing Database system
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Data Design Concepts
Overview of File Processing Can be more efficient and
cost-effective in certain situations
Potential problems Data redundancy Data integrity Rigid data structure
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Data Design Concepts
Overview of File Processing Various types of files
Master file Table file Transaction file Work file Security file History file
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Data Design Concepts
The Evolution from File Systems to Database Systems Advantages
Scalability Better support for client/server systems Economy of scale Flexible data sharing Enterprise-wide application – database administrator
(DBA)
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Data Design Concepts
The Evolution from File Systems to Database Systems Advantages
Stronger standards Controlled redundancy Better security Increased programmer productivity Data independence
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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
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DBMS Components
Interfaces for Users, Database Administrators, and Related Systems Users Database Administrators Related information systems
A DBMS can support several related information systems that provide input to, and require specific data from, the DBMS
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DBMS Components
Data Manipulation Language A data manipulation language (DML) controls database
operations
Schema The complete definition of a database, including
descriptions of all fields, tables, and relationships You also can define one or more subschemas
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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
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Web-Based Database Design
Characteristics of Web-Based Design
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Web-Based Database Design
Internet Terminology Web browser Web page HTML (Hypertext Markup Language) Tags Web server Web site
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Web-Based Database Design
Internet Terminology Intranet Extranet Protocols Web-centric Clients Servers
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Web-Based Database Design
Connecting a Database to the Web Database must be connected to the
Internet or intranet Middleware Adobe
ColdFusion
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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, and the telecommunication links that connect the components of the system
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Data Design Terminology
Definitions Entity Table or file Field
Attribute Common field
Record Tuple
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Data Design Terminology
Key Fields Primary key
Combination key Composite key Concatenated key Multi-valued key
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Data Design Terminology
Key Fields Candidate key
Nonkey field Foreign key Secondary key
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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
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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
A popular method is to represent entities as rectangles and relationships as diamond shapes
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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)
Associative entity
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Entity-Relationship Diagrams
Cardinality Cardinality notation Crow’s foot notation Unified Modeling
Language (UML)
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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)
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Normalization
Repeating Groups and Unnormalized Design Repeating group
Often occur in manual documents prepared by users Unnormalized
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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
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Normalization
Second Normal Form A standard process exists for converting a table from
1NF to 2NF
1. First, create and name a separate table for each field in the existing primary key
2. Next, create a new table for each possible combination of the original primary key fields
3. Finally, study the three tables and place each field with its appropriate primary key
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Normalization
Second Normal Form Four kinds of problems are found with 1NF description
that do not exist with 2NF Consider the work necessary to change a particular
product’s design 1NF tables can contain inconsistent data Adding a new product is a problem Deleting a product is a problem
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Normalization
Third Normal Form 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
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Normalization
A Normalization Example
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Using Codes During System 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
transmission time, and decrease data entry time Can reduce data input errors
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Using Codes During System Design
Types of Codes
1. Sequence codes
2. Block sequence codes
3. Alphabetic codes
a. Category codes
b. Abbreviation codes – mnemonic codes
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Using Codes During System Design
Types of codes
4. Significant digit codes
5. Derivation codes
6. Cipher codes
7. Action codes
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Using Codes During System Design
Developing a Code
1. Keep codes concise
2. Allow for expansion
3. Keep codes stable
4. Make codes unique
5. Use sortable codes
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Using Codes During System Design
Developing a Code
6. Avoid confusing codes
7. Make codes meaningful
8. Use a code for a single purpose
9. Keep codes consistent
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Steps in Database Design
1. Create the initial ERD
2. Assign all data elements to entities
3. Create 3NF designs for all tables
4. Verify all data dictionary entries After creating your final ERD and normalized table
designs, you can transform them into a database
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Database Models
Relational Databases The relational model was introduced during the 1970s
and became popular because it was flexible and powerful
Object-Oriented Databases Many systems developers are using object-oriented
database (OODB) design as a natural extension of the object-oriented analysis process
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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
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Data Storage and Access
Logical and Physical Storage Logical storage
Characters Date element or data item Logical record
Physical storage Physical record or block Buffer Blocking factor
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Data Storage and Access
Data Storage Formats Binary digits Bit Byte EBCDIC and ASCII Unicode - internationalize
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Data Storage and Access
Data Storage Formats Binary
Binary storage format Integer format Long integer format Other binary formats exist for efficient storage of
exceedingly long numbers
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Data Storage and Access
Selecting a Data Storage Format In many cases, a user can select a specific data storage
format For example, when using Microsoft Office, you can store
documents, spreadsheets, and databases in Unicode-compatible form by using the font called Arial Unicode MS
Best answer is it depends on the situation
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Data Storage and Access Date Fields
Most date formats now are based on the model established by the International Organization for Standardization (ISO)
Can be sorted easily and used in comparisons Absolute date Best method depends on how the specific date will be
printed, displayed or used in a calculation
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Data Control
User ID
Password
Permissions
Encryption
Backup
Recovery procedures
Audit log files
Audit fields
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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
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Chapter Summary
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
A code is a set of letters or numbers used to represent data in a system
The most common database models are relational and object-oriented
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Chapter Summary File and database control measures include limiting access to
the data, data encryption, backup/recovery procedures, audit-trail files, and internal audit fields
Chapter 8 complete
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Next Week
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Next Week Quiz-8 from Chapter 8
Practice for next week Quiz Multiple Choice True-False Short Answer Practice Test
Chapter-9: Phase-3 (System Architecture) Phase-3 ends at System Architecture
Home Work Due: North Shore Boat Sales
Class Work from Chapter 9
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Home Work North Shore Boat Sales
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Class Work scsite.com/sad7e/learn
Class Work: Flash Card
– Number of Playing Cards (Type-25)– Type your name: __________– After you done answering 25 question, print the page.
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