Database Record Structure Dania Bilal IS 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 File Origins 101 Ti 2 Don 101 Ti 4 Giovanni 101 Ti 5 Discusses 101 Ab 1 History 101 Ab 3 Sources 101 Ab 5 101 Ab Ab 7 Mozart Used 101 6 Inverted File Mozart 101 DE 1 Opera 101 DE 2 Historical 101 DE 3 Analysis 101 DE 4 101 DE Historical Analysis 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