CHAPTER 13

SYSTEM DESIGN

• Systems design is the process of defining the architecture, components, modules, interfaces, and data for a system to satisfy specified requirements.  
•  Systems design is therefore the process of defining and developing systems to satisfy specified requirements of the user. 
• The logical design of a system pertains to an abstract representation of the data flows, inputs and outputs of the system.   
• The physical design relates to the actual input and output processes of the system.
• This is laid down in terms of how data is input into a system, how it is verified/authenticated, how it is processed, and how it is displayed as output.   To use an analogy, a personal computer's physical design involves input via a keyboard, processing within the CPU, and output via a monitor, printer, etc.   

Alternative design methodologies

1.  Rapid Application Development (RAD) 

• is a methodology in which a systems designer produces prototypes for an end-users. 
• The end-user reviews the prototype, and offers feedback on its suitability. This process is repeated until the end-user is satisfied with the final system.   

2.  Joint Application Design (JAD) 

• is a methodology which evolved from RAD, in which a systems designer consults with a group consisting of the following parties:   

1. Executive Sponsor 
2. System Designer 
3. Managers of the System      

•              JAD involves a number of stages, in which the group collectively develops an agreed pattern for the design and implementation of the system.   

Benefits of System Design 

•         Improved system performance; individually tailored configuration advice demonstrates where improvement is necessary, and how to improve the system to regain lost performance.
•         Customers gain a detailed understanding of how their users use their system. This Usage Profile can be leveraged to develop future architecture changes.
•         Potential to learn of future concerns, allowing customers to take proactive measures to avoid problems.
•         A baseline performance level is established against which benefits can be compared and changes to the system predicted or foreseen.    

       http://clearview-solutions.com/Technology-Consulting.htm     

     

     http://www.physics.ucf.edu/~roldan/laboratory.html

Citation : 

*  http://www.opentext.com/2/global/services-consulting-system-design.htm  

*  http://en.wikipedia.org/wiki/Systems_design 

TOOLS TO USE IN ANALYSIS

Checklists :

• A type of informational job aid used to reduce failure by compensating for potential limits of human memory and attention.
• Consistency and completeness in carrying out a task.
• More advanced checklist would be a schedule, which lays out tasks to be done according to time of day or other factors.
• Often presented as lists with small checkboxes down the left hand side of the page.
• A small tick or checkmark is drawn in the box after the item has been completed.
• For more informations, please refer to http://en.wikipedia.org/wiki/Checklist

http://www.optimum7.com/internet-marketing/new-articles-content/internet-marketing-services-6-point-checklist.html

http://www.istockphoto.com/stock-photo-3555398-checklist.php



Top-down Analysis :

• Breaking down of a system to gain insight into its compositional sub-systems.
• Each subsystem is then refined in yet greater detail, sometimes in many additional subsystem levels, until the entire specification is reduced to base elements.
• This approach makes each component easier to analyze an deal with.
• A top-down model is often specified with the assistance of "black boxes", these make it easier to manipulate.
• However, black boxes may fail to elucidate elementary mechanisms or be detailed enough to realistically validate the model.
• For more information, please refer to http://en.wikipedia.org/wiki/Top-down_and_bottom-up_design

http://www.csc.liv.ac.uk/~frans/OldLectures/2CS21_Ada/week6/topDown.html

http://www.oasisllc.net/deltas/OASIS+Delta+Vol1+Ed6.htm

Grid Charts :

• Show the relationship between input and output.
• On a grid sheet, rows represent inputs; columns represent output documents.
• Intersection between the row and column means that the input document is used to create the output document.

                                         

http://geo.arc.nasa.gov/sge/jskiles/top-down/color_sleuths/color_sleuths.html

Decision Tables :

• Shows the decision rules that apply when certain condition occur.
• A precise yet compact way to model complicated logic of a decision.
• Associate conditions with actions to perform, but in many cases do so in a more elegant way.
• For more informations, please refer to http://en.wikipedia.org/wiki/Decision_table

http://www.methodsandtools.com/archive/archive.php?id=39

http://yourdon.com/strucanalysis/wiki/index.php?title=Chapter_11

System Flowcharts : 

• It is system explains how a system works using a diagram. The diagram shows the flow of data through a system.
• Diagrammatic representation can give a step-by-step solution to a given problem.
• Process operations are represented in these boxes, and arrows connecting them represent flow of control.
• Data flows are not typically represented in a flowchart, in contrast with data flow diagrams; rather, they are implied by the sequencing of operations.
• Flowcharts are used in analyzing, designing, documenting or managing a process or program in various fields.
• For more informations, please refer to http://en.wikipedia.org/wiki/Flowchart , http://www.brainfood.ca/assistant/computing/systems/systemFlowchart.htm , http://www.theteacher99.btinternet.co.uk/theteacher/gcse/newgcse/others/system_flowchart.htm
• ANSI Standard Symbols :

http://www.theteacher99.btinternet.co.uk/theteacher/gcse/newgcse/others/system_flowchart.htm

http://ibcompsci.wikispaces.com/Dossier

Data Flow Diagrams (DFDs) :

• A graphical representation of the "flow" of data through an information system.
• DFDs can also be used for the visualization of data processing (structured design).
• A significant modeling techniquefor analyzing & constructing information process.
• Explains the course @ movement of information in a process.
• The information in DFD is a process based in the inputs & outputs.
• provides no information about the timing of processes, or about whether processes will operate in sequence or in parallel.
• Quite different from a flowchart, which shows the flow of control through an algorithm, allowing a reader to determine what operations will be performed, in what order, and under what circumstances, but not what kinds of data will be input to and output from the system, nor where the data will come from and go to, nor where the data will be stored (all of which are shown on a DFD).
• For more informations, please refer to http://en.wikipedia.org/wiki/Data_flow_diagram , http://www.edrawsoft.com/Data-Flow-Diagrams.php

http://www.dassh.ac.uk/data/data_management.html

http://sunlightlabs.tumblr.com/

Automated Design Tools :

• It is a software packages that evaluate hardware & software alternatives according to requirements given by the systems analyst.
• It also know as computer-aided software engineering(CASE) tools.
• CASE is the scientific application of a set of tools and methods to a software system which is meant to result in high-quality, defect-free, and maintainable software products.
• It also refers to methods for the development of information systems together with automated tools that can be used in the software development process.
• For more informations, please refer to http://en.wikipedia.org/wiki/Computer-aided_software_engineering

Citations :

- http://en.wikipedia.org/wiki/Checklist

- http://en.wikipedia.org/wiki/Top-down_and_bottom-up_design

- http://en.wikipedia.org/wiki/Decision_table

- http://en.wikipedia.org/wiki/Flowchart
- http://www.brainfood.ca/assistant/computing/systems/systemFlowchart.htm
- http://www.theteacher99.btinternet.co.uk/theteacher/gcse/newgcse/others/system_flowchart.htm
- http://en.wikipedia.org/wiki/Data_flow_diagram , http://www.edrawsoft.com/Data-Flow-Diagrams.php

- http://en.wikipedia.org/wiki/Computer-aided_software_engineering