© 2003 mcgraw-hill australia pty ltd, ppts t/a accounting information & reporting systems by a....

© 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

chapter

33Documentation techniques and

databasesLearning 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.



key termskey terms• attribute• binary notation• bit• byte• context diagram• data dictionary• data flow• data flow diagram• data model

• data store• data structure• data warehouse• database• database management

system• decision table• decomposition of a data

flow diagram



key terms (cont.)key terms (cont.)• documentation• entity• E-R diagram• flow charts• flow line• foreign key• lead time• primary key

• relational database model

• relationship• schema• secondary key• subschema



Data flow diagramsData flow diagrams• Graphically describe the flow of data within

an organisation• Composed of four basic elements

represented by standard symbols:



Basic data flow diagramBasic data flow diagram



Data flow diagram for customer Data flow diagram for customer delivery datesdelivery dates



Context diagramsContext 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



Context diagramsContext diagrams• 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



Flow chartsFlow charts• Document physical flows determined after

logical data flows have been documented using data flow diagrams



Flow chart symbolsFlow chart symbols



Advantages and disadvantages of Advantages and disadvantages of flow chartsflow 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



System flow chartsSystem flow charts• Show the relationship between input,

processing and output including data, documents and storage

• Represent the relationship between various processes



System flow chartSystem flow chart



Document flow chartsDocument flow charts• Emphasise the flow of documents between various people,

groups and departments of an organisation



Program flow chartsProgram flow charts• Show the detailed steps of a computer program• Show the logic and processing steps used to develop a

computer program



Decision tablesDecision 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



Decision tablesDecision 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



DatabasesDatabases• 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



DatabasesDatabases• Data warehouse:

– database constructed for ease of use and ad hoc queries

• Data dictionary:– a document that describes each data element in the

database



Types of database modelsTypes 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



Hierarchical database modelHierarchical database model• Also called a tree model, occurs when data is

organised in top-down structure in a one-to-many relationship



Network database modelNetwork database model• An extention of the hierarchical model but takes the

form of a many-to-many relationship



Relational database modelRelational 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....

Documents

logical flow of data

data flow diagrams dfds

basic data flow diagram

mcgrawhill australia

kaye watson

advantages of flow charts

logical data flows

major data flows