© 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 3 Documentation techniques and databases 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. 3-2 key 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

© 2003 McGraw-Hill Australia Pty Ltd, PPTs t/a Accounting Information & Reporting Systems by A. Aseervatham and D. Anandarajah. Slides prepared by Kaye Watson. 3-3 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

© 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 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. 3-5 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. 3-6 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. 3-7 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. 3-8 Context 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

© 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 Relational database model Logical structure that views a database as a collection of two-dimensional tables called database tables