4.3.9 - SDLC - Systems Analysis
- Created by: Annie
- Created on: 13-05-13 18:25
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- Systems Analysis
- What is it?
- Systems Analysis
- Follows the decision to create a new system on the basis of the Feasibility Report
- The purpose is to detail the existing system and further understand the User Requirements
- NOT the new system
- The purpose is to detail the existing system and further understand the User Requirements
- Systems analysis is a detailed job often carried by specialist Systems Analysts
- Poor systems analysis could mean mistakes from the old system are repeated in the new system
- The outcome is a Systems Specification
- Gathering Information
- Interviews
- With managers to reveal how the departments work and current problems
- How they want the new system to work and what information they want
- Operational staff can supply fine detail on how the current system works
- Very time consuming as a lot of people have got to be contacted
- Need skilled interviewers to get the correct information out of people
- Observation
- Sit and watch how somebody does their job at present
- To get a understanding of what they do, how, what information flows, the processes and any time delays, crashes and interruptions
- Can be time consuming
- Sit and watch how somebody does their job at present
- Inspection of records
- Studying paper based information
- Can see what information is currently held and the way it is communicated between different departments, customers and the company
- Can include charts, manuals, reports, minutes of meetings and documentation
- Questionnaires
- Ideal way to collection information as it is least time consuming
- Economical to produce and distribute
- Not everyone may fill them in though and response rates from posted surveys are usually low
- People feel more involved, making the new system seem a positive thing
- Cost involved in hiring people to ask and collect results
- Ideal way to collection information as it is least time consuming
- Interviews
- Tools and Techniques used for Systems Analysis
- Data Flow Diagrams
- To break the system down into
- External sources of data
- Processes of the system
- External "sinks" of data
- 3 Stages
- 1. Context diagram to give an overview of the whole system with system shown as one process
- 2. Level 1 DFD: Breaking down the context diagram - typically has no more than 6 key processes
- Can start to see Entity Relationships
- 3. Level 2 DFD: This break down each process into further detail
- External objects are ovals
- Data flow are arrows
- Processes are tables
- To break the system down into
- Decision Tables
- These can help understand the rules and actions of a system and also how a new system may behave
- They detail the programming decisions that can be made by the computer
- A table is used to structure the information
- Systems Diagrams
- Identify the data coming into the system (inputs)
- What processes happen to the data?
- What outputs are produced by the system?
- Data Dictionaries
- Typically a key feature of the design specification
- The data dictionary needs details about the existing fields and how they are stored at this stage
- Key information needed:
- Entity Names
- Relationships between entities
- Attribute names and synonyms
- Data type
- Length
- Validation to be used
- Primary and foreign keys
- Entity Relationship Diagrams
- To show the relationships between tables
- One to One
- Many to Many
- One to Many
- Many to One
- To show the relationships between tables
- Data Flow Diagrams
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