Jun-Ki Min KUT

 Data & Information ◦ Data: facts or values obtained by observation or measurement ◦ Information: interpretation or relationship to help decision making (semantic)  Data != Information  P(D) = I Data(D) Processor(P) Information(I)

 Information System ◦ For a organization, collect, manage, and store data and generate and distribute information ◦ Application System  A subsystem for a department  Consist of application programs Data Processor Information Decision Make Stored data Real Work

 Information System ◦ MIS: Management Information System  Planning, operation, Control ◦ DSS: Decision Support System  Wide Definition  Data warehouse  Information repository, information archive  Data mining  Knowledge discovery for finding rules or patterns  Knowledge management system

batch processing ◦ Preprocessing  Collection of raw data  Classification and record into file ◦ System oriented processing  High system performance  Low processing cost ◦ Benifical to sequential access method

Raw Data Classificatio n Computer Report File

 real time processing  User oriented Processing ◦ Low system performance ◦ High processing cost  Require communication controller  Overhead for maintenance, recovery

Data Report Data/ Report Database Computer Communication controller

 dispersed processor – Computer System  distributed database  communication network ⊙ client/server pattern

Computer (Client/Server) Database Computer (Client/Server) Database Computer (Client/Server) Database Network

 Origin of “database” Term ◦ The first SDC Symposium  Development and Management of a Computer- centered Data Base ◦ The second SDC Symposium  Computer-centered Data Base Systems

 Database ◦ A collection of interrelated data ◦ For diverse application systems in a enterprise, a set of shared, integrated, stored and operational data  shared data  integrated data ◦ minimal redundancy ◦ controlled redundancy  stored data ◦ Stored media accessed by a computer ◦ Disk, tape, etc  operational data

 real-time accessibilities ◦ real-time processing and response for a query  continuous evolution ◦ update, insert, delete : dynamic feature  concurrent sharing ◦ multi-users use simultaniously  content reference ◦ Not location or address of data ◦ Reference by contents

 logical components ◦ User view ◦ Database = {entities, relationships}  Entity ◦ Object to be represented ◦ Unit of information ◦ Consist of attributes  The smallest logical unit of data ◦ entity set  entity type vs. entity instance ◦ Correspond to general record  record type vs. record instance

 Entity ◦ An object that exists and is distinguishable from other objects ◦ Example  John Harris with SSN  Account #401 at the Redwood Branch of XY bank  Entity Set ◦ A set of entities of the same type ◦ Example  Customer : the set of all persons having an account at a bank  Account : the set of all accounts in XY bank

 Attributes ◦ Properties of entities ◦ A particular entity has a value for each of its attributes ◦ Example :  For the Customer entity set  attributes : customer-name, social security, address  Domain ◦ The set of permitted values for each attribute ◦ Example  Domain of the attribute ‘account-number’  The set of all positive integers

snumnamedept 1234JaneCS 1825JohnEE Attribute Entity type Entity instance Entity Set student …

 attribute relationship ◦ intra-entity relationship: properties  entity relationship ◦ inter-entity relationship student teach professor

 logical organization ◦ conceptual structure by user view ◦ logical allocation of data ◦ A set of logical records  physical organization ◦ physical allocation by storage view ◦ actual structure ◦ Additional information  Index, pointer, chain, overflow area, etc ◦ A set of stored records

A CB D stored record physical system ( storage ) logical record A C B D User logical Record