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Redundancy
College of [email protected]
Copyright © 2007 Patrick McDermott
Philippe de Champaigne (1602-1647) Triple Portrait of Cardinal Richelieu (1585-1642)1642
DRY• Don’t Repeat Yourself• Don’t Say the same Thing Twice• Don’t Reiterate• Don’t go over the same Ground Twice• Don’t say it Again• Only say it Once• One time & One Time Only• No Duplicate Statements
CW-1
Good
New
Lily
Pat
CW-2
HF-1
HF-2
HF-3
Good
New
Fair
Johnny
Mary
Pat
Flat224 pagesHuck Finn 1884 Mark Twain
24 pagesHick Finn 1884 Sam Clemen
64 pagesCall of Wild 1903 Jack London
224 pagesHuck Finn 1884 Mark Twain HF-1
HF-2
HF-3
CW-1
Good
New
Fair
Good
New
88 pagesCall of Wild 1907 Jack London
Johnny
Mary
Lily
Pat
Pat
CW-2
224 pagesHuck Finn 1884 Mark Twain
64 pagesCall of Wild 1903 Jack London
Database
Xtreme!• Department
– The Department of Superfluous Redundancy Department
• The number 7 should appear only once in the entire computer!
• Human languages are extremely redundant– Agree in Gender, Number & Case– Causes Numerous Grammar Errors
Good• If computer does, OK
– Don’t trust Humans (including Programmers)• Replication• Backup• Keys• Performance
– Index is Always Redundant
• Critical or Dangerous: Triple Redundancy• Belt & Braces
Derived Data• Calculated Amount
– Set Counts & Totals• For Efficiency• For Concept/Analysis
– Don’t Forget– Reassure Users– For Data Mining
• “Don’t save anything you can recalculate.” —Raymond Chen, The Old New Thing
