Data, Information and Knowledge

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

2
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

3
Flat Files (2)

• 10021,Smith,John,3 Davis Road,1/5/98,1,apple,6,0.2
  5
• 10021,Smith,John,3 Davis Road,1/5/98,2,orange,3,0.
  30
• 10021,Smith,John,3 Davis Road,1/5/98,3,pineapple,1
  ,1.23
• 10022,Jones,Ann,1 Hastings Way,1/5/98,1,apple,2,0.
  25
• 10023,Jones,Ann,1 Hastings Way,2/5/98,1,banana,5,.
  12

4
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

5
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

6
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

7
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

8
Hierarchical Model (2)
9
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

10
Network Model (2)
11
Relational Model (1)

• Relational Database Management System (RDBMS)
• Currently the most popular form of DBMS
• Access (?)
• Wizards
• Oracle
• SQL, Forms and Triggers

12
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

13
Tables, Records Fields (2)

• Customer Customer
• Family Name Jones,Ann,1 Hastings Way
• Given Name Smith,John,3 Davis Road
• Address Smith,Peter,53 Front Street
• Purchase Order Purchase Order
• Order number 10021,1/5/98
• Date 10022,1/5/98
• 10023,2/5/98
• Purchase Order Line Purchase Order Line
• Line number 1,6
• Number of items 2,3
• 3,1
• 1,2
• 1,5
• Stock Stock
• Item apple,0.25

14
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 objects 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

15
Object Relational Model

• Hybrid database models
• Combines both models
• Really an extension of Relational model
• Longevity?
• Oracle 8
• Multimedia
• Integration with other environments/languages