Transcript Database/Record Structure

Database & Record Structure
Dania Bilal
IS 530
Fall 2005
Definition
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A database is a collection of information
organized in a way that a computer
program can quickly retrieve desired
pieces of data.
Database Components
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Fields
Records
Files
Database Fields
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Pieces of information a user can access
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Author
Title
Journal name
Abstract
Descriptors
Other
Database Fields
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Fields may have attributes associated
with them:
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Numeric
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(e.g., accession number)
Textual
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(e.g., author name)
Database Records and Files
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Record
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A collection of fields which constitutes a
complete set of information
File
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A collection of records
Hypertext Database
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Hypertext was invented by Ted Nelson
in the 1960s.
In a hypertext database, objects (text,
pictures, music, and other media) are
linked to each other.
Data Structure
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A scheme for organizing related pieces
of information.
Basic types of data structures
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Files, records, trees, tables
Trees
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Data is organized in a hierarchical
structure
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Each element is attached to one or more
elements that is directly beneath it.
Connections between elements ->branches
Elements at bottom of a tree with no
elements below them -> leaves
Tables
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Data is organized in rows and columns
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Example: Excel spreadsheet
Relational database management
systems store data in the form of
related tables
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Aleph system is based on a relational database management
system (Oracle)
Dialog Database
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Documents or surrogates are stored in
a linear file
Linear file is transformed into an
inverted file
Dialog Database Structure
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Linear file
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Composed of document surrogates stored
in the IR system in their full, native form.
Inverted file
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Composed of all words included in
document surrogates excluding stop
words.
Linear File
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Documents have to be searched in their
entirety to locate specific information
needed.
Slow and inefficient
Inverted File
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Words in all documents can be searched
instead of the whole text of the
documents themselves
Faster and more efficient
Creation of Inverted File
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A list of words in document surrogates
is made.
Each word is numbered, including
phrases and excluding stop words.
Words that are numbered are
alphabetized (numbers precede letters)
Creation of Inverted File
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Alphabetized entries are followed by the
document number, field (e.g., AB, DE),
and the number of the entry in that
field (e.g., entry in abstract as first
word)
Linear File: Example
101
The origins of Don Giovanni.
Discusses the history and sources Mozart used in
his opera Don Giovanni.
DE: Mozart, Opera, Historical Analysis.
Inverted File
Origins
Don
Giovanni
101
101
101
Ti
Ti
Ti
2
4
5
Discusses
History
Sources
Mozart
Used
…
101
101
101
101
101
Ab
Ab
Ab
Ab
Ab
1
3
5
6
7
Inverted File
Mozart
101
DE
1
Opera
101
DE
2
Historical
101
DE
3
Analysis
101
DE
4
Historical Analysis
101
DE
3,4
Indexing
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Words (keywords)
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Every important word in document is
indexed
Information systems, for example, is
indexed as 2 separate words and as a
phrase
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Information
Systems
Information systems
Record Structure
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Dialog record structure shows every
field followed by the information for
that field.
Fields and structure varies among
databases
Demo of a Dialog Record structure
Internet Protocols
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Http
Telnet
File Transfer Protocol (FTP)
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Secure FTP (SSH)
Web-based FTP (Volspace)
E-mail Protocols
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SMTP (Simple Mail Transfer Protocol)
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Used to send e-mail between servers and between
a server and client’s machine over the Internet
Email is retrieved by using a POP, IMAP, or
text-based email client
POP (Post Office Protocol)
IMAP (Internet Message Access Protocol)
Introduction to Dialog
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Begin or B
Select or S
Select Steps or SS
Display Sets or DS
Logoff hold
Logoff