Representational Tools

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Information about Representational Tools

Published on July 9, 2009

Author: ldunphy



Represenational & Software tools used in the NSW BOS SDD syllabus

Software Design and Development Representational & Software Tools in SDD

Contents Course Specifications 1. Context diagrams 5. Storyboard 2. Data flow diagram 6. Structure Chart 3. Data Dictionary 7. System flowcharts 4. IPO Chart 8. CASE tools NSW BOS Course Specifications

Context Diagram Contents Context diagrams are used to represent entire information systems. The system is shown as • a single process along with • the inputs and outputs (external entities) to the system. TEXT TEXT TEXT • the external entities are connected to the single process by data flow arrows. The symbols used are: Process process a single process representing the entire system as a circle Data Flow data flow representing the flow of data between the single process and external entities External Entity External Entity any person or organisation that provides data to the system or receives data from the system, represented by a box

Data Flow Diagram Contents A data flow diagram provides more detail at a lower level for a context diagram. Data flow diagrams represent the information system as a number of processes that together form the single process of a context diagram. The source of data, its flow between processes and its destination along with data generated by the system is represented.

Data Flow Diagram Contents symbols used Process Circles used to represent processes. Processes are actions process taking place to transform inputs to outputs. Data Flow Curved lines represent data flows between processes, data stores and external entities. Data flows should be named to identify the piece of data. External Entity External Boxes used to represent external entities. These are any item, Entity person or organisation sitting outside the systems that provides data to the system or receives data from the system. Data Store An open-ended rectangle is used to represent a data store. It is a Data Store location where data is stored. It can be in computer format, such as a diskette, or in non-computer format, such as a filing cabinet or an answering machine.

Data Flow Diagram Contents example The example below shows the processes involved in borrowing a video.

Data dictionary Contents examples A data dictionary is a table providing a comprehensive description of each field in the database. •This commonly includes: Field name Data type Data format Field size Description Example •field name Unique eight-digit •data type, UserId Text NNNNNNNN 8 number represented as 0001539 •data format text (incl.. no. of decimal places, if applicable) FirstName Text 25 First name of employee Bill •field size (i.e. no. of characters or field width) Surname Text 25 Surname of employee Smith •Description Date of birth as a short •example. DOB Date DD/MM/YYYY 10 date format 15/07/1982 Rate of pay expressed HourlyPayRate Currency #####.## 8 34.50 in dollars per hour •This is shown in Height in metres, with Height Real #.## 3 1.58 the example on the right. two decimal places FeesPaid Boolean 1 Y or N for Yes or No Y

IPO Chart Contents These charts are used to document • the inputs into a process, • the general nature of the processes performed on this input, and • outputs produced for each task or process in a system. When used in conjunction with a structure chart, one IPO chart should be produced for each lowest level process on the structure chart. The IPO chart is in the form of a table with 3 columns: 1. Input 2. Process 3. Output.

IPO Chart Contents examples The IPO chart is in the form of a table with 3 columns, one for each of Input, Process and Output. Validation of student information: The same information can be expressed in a different format, as follows: Input Process Output System School Library System Student id Read Valid- (read from student student-flag Process Name: Validate student information magnetic card) record Input: Student id Password Compare (read from magnetic card) (read from entered keyboard) password Password (read from keyboard) Check if 0 if correct correct 1 if incorrect Process: Read student record Student id Compare entered password Check if correct Output: Valid Student Flag (0 if valid, 1 if invalid)

Storyboards Contents Storyboards are used to document the screens used in a system, and the flow between them. • Screens should contain sufficient detail to indicate the general layout of • Text • Fields • Graphics • Buttons • The flow between screens is indicated by the use of arrows. • Where a button click causes the movement to the next screen, the arrow should start from the appropriate button. The storyboard example shows the relationship between three pages of information aimed at promoting a school canteen on a website. Elements of each screen are clearly identified and the links between screens shown.

Structure Chart Contents Structure diagrams allow the representation of a system broken down into its separate • subtasks or • processes. The relationship between each of these processes should also be evident from the diagram. Rectangles are used to represent tasks, with lines used to show the connections between tasks. The chart is read from: • top to bottom, with component subtasks on successively lower levels, and from • left to right to show the order of execution of tasks at the same level.

Structure Chart Contents symbols used The symbols used in Structure Charts are: Data movement between tasks (usually passed as parameters) is shown with the use of arrows. A filled circle is used to indicate a flag. A decision (ie optional execution of a task) is indicated by use of a small diamond at the intersection of the line. Repetition (execution of a particular task multiple times) is shown by a circular arrow.

Structure Chart Contents example The following example illustrates the features of a Structure Chart:

System Flowcharts Contents Data dictionary System flowcharts are a diagrammatic way of representing both the • flow of data and • logic through an information system. They were once the primary tool for documenting systems; however, data flow diagrams are often used instead. 1. Standard flowcharting symbols are used along with 2. Symbols for representing physical devices that • Capture data • Store data • Display data. N.B. Many of these symbols have become out of date as a result of changes in technology.

System Flowcharts Contents symbols used Symbols used in System Flowcharts Data dictionary

CASE Tools CASE tools software must allow the production and maintenance of: • Manuals, incorporating • screen shots • table of contents • index • Flowcharts • Gantt charts • Data dictionary • System flowcharts • Modelling tools such as: • Structure charts • Data flow diagrams •Other appropriate modelling tools. Recommended software: • Word processing • Spreadsheet • Drawing packages with appropriate graphics items. • CASE Tools such as • Ascent • together-J • Rational Rose.

Gantt Chart Gantt charts display the overall timeline for a project. They present a sequential breakdown of individual tasks showing the relationship between tasks and the time taken for each task. The duration of tasks are shown as horizontal bars. Gantt charts should have labelled axes: • Y-axis for tasks and • X-axis for time. A time scale should be shown, including dates. Milestones should also be included.

Gantt Chart example The example below shows the main elements of a Gantt chart.

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