University of Sunderland COMM2Q Unit 1 COMM2Q Lecture 1 HIS Application Building

University of Sunderland COMM2Q Unit 1 Data, Information and Knowledge Data –Details that are meaningless because they lack relevance Information –Data presented or received in a form that is meaningful, has real or perceived value and adds to existing knowledge Knowledge –Complete/Incomplete awareness of things that are potentially useful

University of Sunderland COMM2Q Unit 1 Flat Files (1) Flat File Structure –Rows –Each row represents a single Record –Records end with a New Line and Carriage Return –Columns –Every record consists of the same number of elements/Fields –Fields are separated from one another with characters such as a comma

University of Sunderland COMM2Q Unit 1 Flat Files (2) 10021,Smith,John,3 Davis Road,1/5/98,1,apple,6, ,Smith,John,3 Davis Road,1/5/98,2,orange,3, ,Smith,John,3 Davis Road,1/5/98,3,pineapple,1, ,Jones,Ann,1 Hastings Way,1/5/98,1,apple,2, ,Jones,Ann,1 Hastings Way,2/5/98,1,banana,5,.12

University of Sunderland COMM2Q Unit 1 Problems with Flat Files Duplication/break-up of information An increase in the time and effort required to enter data An increase in the risk of error in entering the data wrong Have to write programs to access data

University of Sunderland COMM2Q Unit 1 Databases Database Management System (DBMS) When one or more files are managed within a single application Offers a programming language to manipulate data Usually provides interface development environment

University of Sunderland COMM2Q Unit 1 Modelling The efficient storage of data and the effective retrieval of information Divides area of concern into: Data –How it is stored Process –What is done with it Event –When it occurs

University of Sunderland COMM2Q Unit 1 Hierarchical Model (1) The earliest of the widely used models Each node holds a segment of a potentially much larger record One to many, higher to lower Get what you want rather than everything Grandparent - parent - child But only one parent and no brothers Efficient if data can be organised that way No child without a parent Getting rid of the parent destroys the child

University of Sunderland COMM2Q Unit 1 Hierarchical Model (2)

University of Sunderland COMM2Q Unit 1 Network Model (1) Allows for multiple parents Relationships One to one One to many Many to many A more complex form of hierarchy More flexible and user-friendly As rigid in its modelling

University of Sunderland COMM2Q Unit 1 Network Model (2)

University of Sunderland COMM2Q Unit 1 Relational Model (1) Relational Database Management System (RDBMS) Currently the most popular form of DBMS Access (?) –Wizards Oracle –SQL, Forms and Triggers

University of Sunderland COMM2Q Unit 1 Tables, Records & Fields (1) In a RDBMS Files are replaced with Tables/Relations Columns are replaced with Fields/Attributes Rows are replaced with Records/Tuples Tables only deal with data items that are meaningfully associated with that table

University of Sunderland COMM2Q Unit 1 Tables, Records & Fields (2) Customer Family NameJones,Ann,1 Hastings Way Given NameSmith,John,3 Davis Road AddressSmith,Peter,53 Front Street Purchase OrderPurchase Order Order number10021,1/5/98 Date10022,1/5/ ,2/5/98 Purchase Order LinePurchase Order Line Line number1,6 Number of items2,3 3,1 1,2 1,5Stock Itemapple,0.25 Cost of itemorange,0.30 pineapple,1.23 banana,0.12

University of Sunderland COMM2Q Unit 1 Object Model Traditional systems support traditional modelling Data layer - Tables/Relationships Process layer - Queries Event Layer - Macros and Modules Object modelling, the focus is the object An object’s data and processing are stored together The nature of the objects and their associations is different e.g. ‘is a kind of’’, ‘is part of’, ‘works on’ Descriptions can be translated into OO concepts, which are the basis for OODBMS A new technology for an established model

University of Sunderland COMM2Q Unit 1 Object Relational Model Hybrid database models Combines both models Really an extension of Relational model Longevity? Oracle 9 Multimedia Integration with other environments/languages