Database & Record Structure Dania Bilal IS 530 Fall 2007

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

Fields Attributes Numeric Textual (e.g., accession number) (e.g., author name)

Data Structure A scheme for organizing related pieces of information. Basic types of data structures Files Records Trees Tables

Files File Every file/database has a number and/or a name A collection of records In Dialog, a file also refers to a specific database Every file/database has a number and/or a name ERIC is a database with a file no. 1 in Dialog.

Records Record A collection of fields which constitutes a complete set of information Author, title, journal name, abstract, etc. A collection of records constitutes a file.

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 Example: Yahoo directory.

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 called 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, original 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. Audiocassette is an analogy to a linear structure Slow and inefficient

Inverted File Words in all documents can be searched instead of the whole text of the documents themselves Music CD is an analogy to an inverted structure. Faster and more efficient

Dialog Inverted File A list of words in each document surrogate is made. Each word is numbered, including phrases and excluding stop words (the, a, an, etc.). Words that are numbered are alphabetized (numbers precede letters).

Dialog Inverted File Alphabetized entries are followed by the document number, the field it is from (e.g., AB, DE), and the number of the entry in that field.

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 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 a document is indexed Example: Information systems Indexed as 2 separate words and as a phrase Information (word) Systems (word) Information systems (phrase)

Indexing Exercise Index a paragraph from Dr. Bilal’s Web page (under research and publications) Extract the keywords from the first line of the paragraph Indicate the position of each word and the field it appears in

Demos Demo of a Dialog Record structure Demo of an Ebsco database record structure Demo of a Web page record structure (html markup language and/or other languages) Demo of a record structure in Aleph