Download Chapter 3

chapter
Documentation
techniques and
databases
3
Learning objectives
– To learn about data flow diagrams (DFDs) and the symbols
used in them.
–To understand a context diagram and its decomposition.
–To understand the standard symbols used in flow charts.
–To describe and construct different types of flow charts.
–To understand the advantages of flow charts over written
descriptions.
–To be able to compare and contrast DFDs and flow charts.
–To understand decision tables and their relevance to
programming.
–To learn about the construction of E-R diagrams as a
basis for databases.
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-1
key terms
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attribute
binary notation
bit
byte
context diagram
data dictionary
data flow
data flow diagram
data model
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data store
data structure
data warehouse
database
database management
system
• decision table
• decomposition of a data
flow diagram
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
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key terms (cont.)
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documentation
entity
E-R diagram
flow charts
flow line
foreign key
lead time
primary key
• relational database
model
• relationship
• schema
• secondary key
• subschema
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
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Data flow diagrams
• Graphically describe the flow of data within an
organisation
• Composed of four basic elements
represented by standard symbols:
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-4
Basic data flow diagram
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-5
Data flow diagram for customer
delivery dates
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-6
Context diagrams
• Show major data flows into and out of a system
• Describe each subsystem as a process showing
interrelationship of those subsystems and their relationship
to main system
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-7
Context diagrams
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Depict logical flow of data in summary form
The starting point for studying any system
Depict the system at its highest level
Referred to as level zero data flow diagrams
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-8
Flow charts
• Document physical flows determined after
logical data flows have been documented
using data flow diagrams
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-9
Flow chart symbols
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-10
Advantages and disadvantages of
flow charts
• Advantages:
– Enable any system to be represented in easily understandable
manner
– Overall picture of system easily seen
– Highlight relationship among different parts of the system
• Disadvantages:
– Creation can be time-consuming
– Numerous symbols can be confusing
– Process may not be completely representable using symbols
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-11
System flow charts
• Show the relationship between input,
processing and output including data,
documents and storage
• Represent the relationship between various
processes
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-12
System flow chart
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-13
Document flow charts
• Emphasise the flow of documents between various people,
groups and departments of an organisation
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-14
Program flow charts
• Show the detailed steps of a computer program
• Show the logic and processing steps used to develop a
computer program
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-15
Decision tables
• List the decision logic of a program flow chart in tabular form
• Constructed with two main columns and two rows:
– First row is further divided into a number of rows of conditions
– Second row is further divided into a number of rows of actions
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-16
Decision tables
• The decision table tells us the following:
– if stock is not available and floor stock is not being sold, collect
10% advance
– if stock is available but delivery is not within three days, collect
10% advance
– if stock is available and delivery within three days, collect full
value of sale
– if stock is not available but floor stock is being sold within three
days, collect full value of sale
– if stock is not available but floor stock is being sold after three
days, collect 10% advance
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
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Databases
• Database:
– the actual physical repository for an organisation’s data
• Database management system (DBMS):
– a computer program that allows authorised users to
update files, select and retrieve data
– acts as an interface between database and application
programs
• Data structure:
– the technique of physically arranging records in a
database
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-18
Databases
• Data warehouse:
– database constructed for ease of use and ad hoc queries
• Data dictionary:
– a document that describes each data element in the
database
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-19
Types of database models
• Database management systems use different
structures depending on the needs of the
particular system:
– Hierarchical database model
– Network database model
– Relational database model
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-20
Hierarchical database model
• Also called a tree model, occurs when data is
organised in top-down structure in a one-to-many
relationship
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-21
Network database model
• An extention of the hierarchical model but takes the
form of a many-to-many relationship
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
3-22
Relational database model
• Logical structure that views a database as a
collection of two-dimensional tables called database
tables
© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information &
Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by
Kaye Watson.
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