Database & Record Structure

Dania BilalIS 530

Fall 2005

Definition A database is a collection of

information organized in a way that a computer program can quickly retrieve desired pieces of data.

Database Components Fields Records Files

Database Fields Pieces of information a user can

access Author Title Journal name Abstract Descriptors Other

Database Fields Fields may have attributes

associated with them: Numeric

(e.g., accession number) Textual

(e.g., author name)

Database Records and Files Record

A collection of fields which constitutes a complete set of information

File A collection of records

Hypertext Database 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 A scheme for organizing related

pieces of information. Basic types of data structures

Files, records, trees, tables

Trees Data is organized in a hierarchical

structure 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 Data is organized in rows and

columns Example: Excel spreadsheet

Relational database management systems store data in the form of related tables

Aleph system is based on a relational database management system (Oracle)

Dialog Database Documents or surrogates are

stored in a linear file Linear file is transformed into an

inverted file

Dialog Database Structure Linear file

Composed of document surrogates stored in the IR system in their full, native form.

Inverted file Composed of all words included in

document surrogates excluding stop words.

Linear File Documents have to be searched in

their entirety to locate specific information needed.

Slow and inefficient

Inverted File Words in all documents can be

searched instead of the whole text of the documents themselves

Faster and more efficient

Creation of Inverted File 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 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 FileOrigins 101 Ti 2

Don 101 Ti 4

Giovanni 101 Ti 5

Discusses 101 Ab 1

History 101 Ab 3

Sources 101 Ab 5

Mozart 101 Ab 6

Used 101 Ab 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 Words (keywords)

Every important word in document is indexed

Information systems, for example, is indexed as 2 separate words and as a phrase

Information Systems Information systems

Record Structure 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 Http Telnet File Transfer Protocol (FTP)

Secure FTP (SSH) Web-based FTP (Volspace)

E-mail Protocols SMTP (Simple Mail Transfer Protocol)

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 Begin or B Select or S Select Steps or SS Display Sets or DS Logoff hold Logoff