System Life cycle Flashcards
System Life cycle
System Analysts will review an existing system which is currently not meeting expectations of the client. An a new system which is fit for the purpose will be developed
Stages in system life cycle
1-Analysis: Collecting information about the present system and identifying problems.
2-Design: Designing a new system to correct the problems identified in the analysis.
3-Development & Testing: Developing and testing new system.
4-Implementation: Replacing the old system with the new system.
5-Documentation: Creating technical and user documentation for new system.
6-Evaluation: Evaluating whether the new system meets the requirements of the design requirements
Analysis
Finding out how the current system works and what the requirements of the client are for the new system
Methods of research (Analysis):
-Questionaries
-Interviews
-Observations
-Document Analysis
Questionaries:
-Used when information is required from a large number of users when it would be impractical to interview them all.
-A mixture of multiple-choice questions, opinion ratings and open-ended questions should be used. This will provide a balance of quantitative analysis of closed-ended questions and a qualitative analysis of open-ended questions where users are able to suggest alternative ideas to those presented by the questionnaire.
-If Questionaries are completed online, results are immediately stored and readily available for detailed analysis in the form of graphs and tables
Advantages and Disadvantages of Questionnaires:
Advantages
-Large audience can be reached
-Questions can be answered quickly such as multiple choice
Disadvantages
-Questions may not be completely accurate
-May not all be returned, if questionnaire takes too long to complete
Interviews
-Interviews involve a direct conversation between the analyst and the client.
-When there is a single end user or small group of end users then interviews are the perfect solution, because questions can be asked of the users and a conversation can take place which can expand upon answers that are given with follow-up questions searching for further detail.
Advantages & Disadvantages of Interviews:
Advantages
-It allows to probe more into the problem
-It allows the analyst to get honest opinions of the employees
Disadvantages
-It can be time consuming
-The analyst cannot remain anonymous with this method
Observation
-Observation involves the analyst watching the processes that take place within an organization to find out how everyday tasks are completed.
-This can involve sitting with users to understand the tasks they have to complete, with an opportunity to ask questions, to elicit further information that could be needed for a requirement specification
Advantages & Disadvantages of Observations
Advantages:
-It obtains reliable data
-It is an inexpensive method
Disadvantages
-People are generally uncomfortable being watched
-People may perform differently when being watched.
Document analysis
-Existing documents within an organization can tell an analyst a lot about the information that is currently being used.
-The analyst will need to see examples of any documents that show output information or give an indication of what data is being collected for input to a system
Advantages & Disadvantages of document analysis
Advantages
-Analyst can view how the current paperwork operates
-This method can give critical information of the system
Disadvantages
-Time consuming method
-Can be a costly method
Types of Specifications
-Requirement specifications
-System specifications
-Design Specification
Requirement specifications
-A requirements specification is a contract between the developer and the client. Created by the analyst.
-It will specify exactly what the client needs the system to do thus developer can produce a system that meets the client’s needs.
What should requirements specification include
1.The purpose of the system.
2.The main objectives of the system.
3.Data that must be output from the system (for example, invoices, sales reports).
4.Data that needs to be input to the system to generate the outputs, including any screens or data collection forms.
5.Validation and verification that is needed for input data.
6.Processes that need to take place to convert inputs into outputs or to store data.
7.Data that need to be stored.
8.Functional requirements such as performance measures.
9.Deadlines for each milestone within the project.
System specifications
The hardware and software needed to run the system
-The software needs to be identified first as the hardware will depend upon what software is needed.
-There may be different software identified for different types of users and for servers. Thus software required to run the system must be specified
-Once the software is known, the minimum hardware required to run that software can be identified. The analyst needs to consider how much storage space is going to be required for the data being used by the system, May also recommend higher than minimum specifications so that the system functions at a reasonable speed.
Design Specification
Illustration of how the system will look, what the data structures will be and how the system will work
- It is intended to give the user an idea of what the system will look like before it is developed so that the user’s feedback can be incorporated into the final designs.
The developer will then follow the designs (Design specifications).
-flowcharts
-data flow diagrams
-data collection forms
-screen layouts
-validation routines
-data dictionary.
In addition to this, a design specification will include: * house style (logos, colors, fonts, styles, sizes) * screen sizes * connectivity diagram to show links between screens * purpose of calculations.
Design
-Design: The stage in the life cycle when the design specification is produced
-During the design stage, the overall structure of the system and details of the system components are designed without being developed.
Data flow diagram (DFD)
Shows how data flows throughout a system. It is not about the order of processes, purely about data flow.
Level 0 DFD
Should identify the external entities and the data flows between the external entities and the system.
Level 1 DFD
-First identify any external entities and any other parts of the system that will be classed as external entities.
-Identify the data flows to and from those external entities. Each data flow must have a process attached to it.
-A data flow cannot move directly from one external entity to another or from one data. store to another.
System Flowchart:
An overview of how the system works in a diagrammatic format
-A system flowchart shows the flow of data and processes within a complete system.
-A system flowchart will show how various elements of an information system are related.
Data Store
-Data Dictionaries
-Files
Data Dictionaries
-Created to describe how data will be stored in tables within a database. The field names should be identified along with their data type,field size and format.
-Primary keys and foreign keys be identified, including the names of tables to which the foreign keys link to.
-Any input masks, validation rules or default values should be identified for each field along with an example of what typical data might look like.
Files
Any files that will be used to import data should be designed, including the intended layout of data. Similarly, any files generated by the system should be designed, including the format in which the data will be exported.
Input Forms
-Data collection forms
-Screen layouts
-Validation Routines
Data Collection forms
Data collection forms are documents that are used to collect data without the use of a computer. These could include membership application forms, questionnaires, job applications or reply to slips.
Principles to follow when designing data collection forms:
1.Avoid color as the document may not be printed in color.
2.Include instructions about how to complete the form.
3.Give clear instructions about where the form should be returned.
4.Identify which questions must be answered and which are optional.
5.Provide enough space for each answer.
6.Use tick boxes for multiple choice lists.
7.Make it clear how many options are allowed to be chosen from a multiple-choice list.
8.Ensure all fonts are consistently used.
9.Avoid cluttering the form with too much information or too many questions.
10.Ensure the font style and size are legible.
11.If the respondent needs to complete a scale (e.g., 1–10), then explain what the scale represents (e.g., 1 = very dissatisfied, 5 = neither satisfied nor dissatisfied, 10 = very satisfied).
Screen layouts:
-A screen can be used to ask the user for data to be input or to display information to the user or a mixture of both.
Principles to follow when designing a screen:
1.Use color sparingly and appropriately; (colors that are usually seen as a positive color and red as a negative color.
2.Ensure all fonts are used with consistency.
3.Avoid cluttering the screen with too much Information.
4.Ensure the font style and size are legible.
5.Complete the form identify which questions must be answered and which are optional.
6.Provide enough space for each answer.
7.Use tick boxes for multiple choice lists that can have more than one response.
8.Use drop-down boxes (combo boxes) or option buttons (radio buttons) for multiple choice lists that can only have one response.
Validation Routines
Validation rules should be used wherever possible and be appropriate to reduce the number of possible input errors. They only need to be used for input data so any calculations or output data do not require validating.
Output reports
-Printed copy layouts
-Paper-based forms
Printed copy layouts
When designing a printed copy layout, consideration needs to be made to the size of paper that will be used, the size of margins and the intended audience. Printed copies can often include tabular data
Paper-based forms must include
1-Proper heading.
2-Text boxes to limit the amount of information.
3-Tick boxes to make choice easier.
4-Sufficient space to write answers.
5-Use clear fonts and clear text colors.
Development
The stage in the system life cycle when the software is produced.
