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What is the General Algorithm?
N How many stepsto reach a leaf?
LogM(N), where M = “branching factor?
M
4 branch trees
If I double the number of branches, what happensto the number of steps to reach a leaf?
4 branch trees
If I double the number of branches, what happensto the number of steps to reach a leaf?
It is cut in half
N branches
• If I have N leaves, why not just have N branches in the tree?
– I can reach each leaf in one step
• The time to choose a leaf– Binary tree
• constant time
– N-ary tree (N branches)• N checks (one for each branch)
Trees - time to find things
• Number of branches (B)– logB(N)– Too many branches
• searching for branches is a problem
– Too few branches • too many steps to a leaf
• Balance• Probability of correct choice
Dewey
• 000 Computers, information, & general reference• 100 Philosophy & psychology• 200 Religion• 300 Social sciences• 400 Language• 500 Science• 600 Technology• 700 Arts & recreation• 800 Literature• 900 History & geography
Dewey
• 500 Science– 510 Mathematics– 520 Astronomy – 530 Physics– 540 Chemistry – 550 Earth sciences & geology – 560 Fossils & prehistoric life – 570 Biology & life sciences – 580 Plants (Botany)– 590 Animals (Zoology)
Dewey
• 500 Science– 550 Earth sciences & geology
• 551 Geology, hydrology, meteorology• 552 Petrology• 553 Economic geology• 554 Earth sciences of Europe• 555 Earth sciences of Asia• 556 Earth sciences of Africa• 557 Earth sciences of North America• 558 Earth sciences of South America• 559 Earth sciences of other areas
What are the numbers in the Dewey tree?
• A path name
• How many possibilities?– 1000
• Where do we get more?– 343.123 c
Using the Dewey tree
• What is the Dewey Decimal number for Ostriches?
• If we don’t know how to choose then how do we find things?
• Search to get Dewey decimal number
What good is the system?
• If we can’t correctly choose the path to a book, then isn’t the search just linear (N/2)?
• Unique location for each book– Why not just assign them a number as each
book comes into the library?
• Browsing - keep related books together
Library of Congress
• How many books?~ 20 Million
• How many maps, documents, videos, photos?~ 100 Million
Library of Congress• A -- GENERAL WORKS• B -- PHILOSOPHY. PSYCHOLOGY. RELIGION• C -- AUXILIARY SCIENCES OF HISTORY• D -- HISTORY: GENERAL AND OLD WORLD• E -- HISTORY: AMERICA• F -- HISTORY: AMERICA• G -- GEOGRAPHY. ANTHROPOLOGY. RECREATION• H -- SOCIAL SCIENCES• J -- POLITICAL SCIENCE• K -- LAW• L -- EDUCATION• M -- MUSIC AND BOOKS ON MUSIC• N -- FINE ARTS• P -- LANGUAGE AND LITERATURE
• Q -- SCIENCE• R -- MEDICINE• S -- AGRICULTURE• T -- TECHNOLOGY• U -- MILITARY SCIENCE• V -- NAVAL SCIENCE• Z -- BIBLIOGRAPHY. LIBRARY SCIENCE. INFORMATION RESOURCES (GENERAL)
Library of Congress• A -- GENERAL WORKS• B -- PHILOSOPHY. PSYCHOLOGY. RELIGION• C -- AUXILIARY SCIENCES OF HISTORY• D -- HISTORY: GENERAL AND OLD WORLD
• E -- HISTORY: AMERICA• F -- HISTORY: AMERICA• G -- GEOGRAPHY. ANTHROPOLOGY. RECREATION• H -- SOCIAL SCIENCES• J -- POLITICAL SCIENCE• K -- LAW• L -- EDUCATION• M -- MUSIC AND BOOKS ON MUSIC• N -- FINE ARTS• P -- LANGUAGE AND LITERATURE• Q -- SCIENCE• R -- MEDICINE• S -- AGRICULTURE• T -- TECHNOLOGY
• U -- MILITARY SCIENCE• V -- NAVAL SCIENCE• Z -- BIBLIOGRAPHY. LIBRARY SCIENCE. INFORMATION RESOURCES (GENERAL)
Why do these subjectsget so much spacein the tree?
What is the purposeof the Library ofCongress?
Organizing trees of information
• Branches
• Balance
• Can the user make a correct choice– Information about each choice
Which of these things is not like the others?
• If you are in first grade?
• If you are a biologist?
Which of these things is not like the others?
• Studying the arctic
• Studying child/adult animal behavior
Yahoo.com - a huge tree of WWW information
What are the majoritems for?
Why are the minoritems here?
Click Here
Aliases - connect tree branches
LiteratureNovels
Whales. . .
IndustrySea
Whaling. . .
BiologyMammals
WhalesStoriesIndustry
. . .
Aliases - Windows Shortcuts
• Named objects that contain the path name of other objects
• Lets us organize a tree in many ways
Shortcut symbol
Challenge
• If you run a commercial art house and want to organize all of your pictures into a tree
• If you are creating a new program and want to organize your menu items into a tree
• Who has the answer to the organization?– The users
How to get user input
• Get samples– 100 pictures – Names of menu items on 3x5 cards
• Give them to users– Tell them to organize them into 7-12 stacks– Tell them to write name on each stack– Video tape the process and ask them to talk
about what they are doing