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CHAPTER 9
Data Design, that interact with
the information system, that…
CHAPTER 9
Data Design
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Web-Based
Characteristics :
:<3:Global access
:<3: Ease of use
:<3: Multiple platforms
:<3: Cost effectiveness
:<3: Security issues
:<3:Adaptability issues
Internet Terminology :
:<3: Web browser
:<3: Web page
:<3: Hypertext Markup Language (HTML)
:<3: Tags
:<3: Web server
:<3: Web site
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Data Design
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Key Field :
:black_flag: Primary key
:black_flag: Candidate key
:black_flag: Foreign key
:black_flag: Secondary key
Referential Integrity :
:black_flag: Validity checks can help avoid data input errors
:black_flag: Referential integrity means that a foreign key value cannot be entered in one table unless it matches an existing primary key in another table
:black_flag: Orphan
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Normalization
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1NF
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To convert, you must expand the table's primary key to include the primary key of the repeating group
2NF
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If it is in 1NF and it all fields that are not part of the primary key are functionally dependent on the entire primary key
3NF
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To convert, you must remove all fields from the 2NF table that depend on another nonkey field
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Using Codes
Types :
- Sequence codes
- Block sequence codes
- Alphabetic codes
4.Significant digit codes
- Derivation codes
- Cipher codes
- Action codes
Developing a Code :
- Keep codes concise
- Allow for expansion
- Keep codes stable
- Make codes unique
- Use sortable codes
- Avoid confusing codes
- Make codes meaningful
- Use a code for a single purpose
- Keep codes consistent
Data Storage and Access
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:!: Logical Storage
- Character
- Data element or data item
- Logical rercord
:!: Physical Storage
- Physical record or block
- Buffer
- Blocking factor
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Data Control
:check: User ID
:check: Password
:check: Permissions
:check: Encryption
:check: Backup
:check: Recovery procedures
:check:Audit log files
:check:Audit fields
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