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Acca 12 (systems analysis-user-requirements)

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Investigating user requirements …

Investigating user requirements
Process models (DFD and Flowcharts)

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  • 1. 1 1 SYSTEMS ANALYSIS USER REQUIREMENTS (1) Lecture 12 Abdisalam Issa-Salwe Thames Valley University Abdisalam Issa-Salwe, Thames Valley University 2 Topic list  Investigating user requirements  Process models (DFD and Flowcharts)
  • 2. 2 Abdisalam Issa-Salwe, Thames Valley University 3 Investigating user requirements  Fact finding:  by means of questionnaires, interviews, observations, reading hand manuals, organisational charts, etc  Fact recording:  using flowcharts, decision tables, narrative descriptions, organisation and responsibility  Evaluation:  assessing strength and weakness of the existing system Abdisalam Issa-Salwe, Thames Valley University 4 Systems Investigation  Techniques used in gathering information to investigate the present system include:  Interviews  Questionnaires  Observation and inspection of records
  • 3. 3 Abdisalam Issa-Salwe, Thames Valley University 5 Interviews  Interviews with members of staff can be the most effective method of fact-finding.  Guidelines exists for conducting the interview.  Rather than following a standard routine, the interviewer must be able to adapt his approach to suit the individual interviewee and should be fully prepared for the interview. Abdisalam Issa-Salwe, Thames Valley University 6 Interviews (cont…)  The interviewer should:  Inform the employee prior to the interview that a systems investigation is taking place, explaining its purpose  Ask questions at a level appropriate to the employee’s position within the organisation  Not be too formal, encouraging the employee to offer opinions and suggestions  Not jump to conclusions or confuse opinion with fact
  • 4. 4 Abdisalam Issa-Salwe, Thames Valley University 7 Questionnaires  Use of questionnaires are useful when a limited amount of information is required from a large number of individuals, or when the organisation is decentralised with many separate locations  Questionnaires may be used in advance of interviews to save the analyst’s and employee’s time Abdisalam Issa-Salwe, Thames Valley University 8 Observation  Having gained an understanding of the methods and procedures used in the organisation  Observation is a useful way of cross- checking with the facts obtained by interview or questionnaire  Different methods of recording facts ought to produce the same information, but it is not inconceivable that staff do their work one way, while management believe that they do something different
  • 5. 5 Abdisalam Issa-Salwe, Thames Valley University 9 User workshops  A workshop is a meeting with the emphasis on practical exercise  User input is obtained by the analyst to analyse business functions and define the data associated with the current and future system  The workshop may devise to plan for implementation  Facilitator to facilitate the workshops. Facilitator coordinates the workshop activities Abdisalam Issa-Salwe, Thames Valley University 10 User workshops (cont…)  Many user workshop may utilise a scribe. The scribe is an active participants who is responsible for producing the outputs of the workshops.
  • 6. 6 Abdisalam Issa-Salwe, Thames Valley University 11 Document review  The system analyst must investigate the documents that are used in the system for input and output.  This may be a wide range investigation, using for example organisational charts, procedures manuals and standard operational forms. Abdisalam Issa-Salwe, Thames Valley University 12 Existing computerised systems  Existing computer systems can provide much information relevant to the requirements for a new computerised system.  It is important to remember however that a duplicate of the existing system is not required. The aim is to produce a better system which is likely to involve changes to existing working methods.
  • 7. 7 Abdisalam Issa-Salwe, Thames Valley University 13 Existing computerised system (cont…)  Area were an existing system could provide useful information include:  File structures  Transaction volume  Screen design  User satisfaction  User complaints  Help-desk/information centre records  Causes of system crashes  Processor speed Abdisalam Issa-Salwe, Thames Valley University 14 Systems Analysis Systems analysis is a detailed look at a current system and what a new system will be required to do:  Leads on directly to systems design, which is the development of a new system that will meet these requirements  Systems analysis is carried out by a systems analyst, who may either by an employee, or an external consultant  The chief analyst, preferably the one who was also responsible for the feasibility studies, will work with a team of individuals with differing backgrounds and experience (technical and business)
  • 8. 8 Abdisalam Issa-Salwe, Thames Valley University 15 Systems Analysis (cont…)  The chief analyst, preferably the one who was also responsible for the feasibility studies, will work with a team of individuals with differing backgrounds and experience (technical and business) Abdisalam Issa-Salwe, Thames Valley University 16 Systems Analysis (cont…) Systems analysis might be done in two stages, depending on the size of the project:  First stage occurs during the feasibility study, since this requires detailing the current system and the requirements for a new system  the second stage in the systems analysis work might be a closer analysis – leading straight into design work
  • 9. 9 Abdisalam Issa-Salwe, Thames Valley University 17 Analysing information flows  Where does information originate? (Might come from multiple sources. )  Which parts should be automated? (Some things are easier to do without computers).  Which automated parts should be integrated?  What other systems are involved?  And what information do they contain? Abdisalam Issa-Salwe, Thames Valley University 18 Analysis & Design Methods (cont…)  Data flow diagrams (DFDs), including context diagrams  Entity Relationship (ER) Diagram  Event lists (Entity Life History)  Pseudocode Data flow diagrams show how information is passed around Entity Relationship Models show what information is stored and how it is inter-related Entity Life Histories show how information is changed during its lifetime
  • 10. 10 Abdisalam Issa-Salwe, Thames Valley University 19 Data flow diagrams (DFDs)  DFDs show functional decomposition, with an emphasis on the transfer of data in and out of the system and between program units.  DFDs examine how data flows into, out of, and within the system. Abdisalam Issa-Salwe, Thames Valley University 20 Data flow diagrams (DFDs) (cont…)  A Data Flow Diagram is a picture of the movement of data between external entities and the processes and data stores within a system.  Systems analysts use data flow diagrams to help them model the processes internal to an information system and how data from the system’s environment enter the system, are used by the system, and are returned to the environment.  DFDs help analysts understand how the organization handles information and what its information needs are or might be.  Analysts also use DFDs to study alternative information handling procedures  During the process of designing new information services.
  • 11. 11 Abdisalam Issa-Salwe, Thames Valley University 21 Abdisalam Issa-Salwe, Thames Valley University 22
  • 12. 12 Abdisalam Issa-Salwe, Thames Valley University 23 DFD Notation Abdisalam Issa-Salwe, Thames Valley University 24
  • 13. 13 Abdisalam Issa-Salwe, Thames Valley University 25 Abdisalam Issa-Salwe, Thames Valley University 26 Data flow diagrams (DFDs) (cont…) A data flow diagram is incomplete unless all its symbols are labeled as follows:  Data flow— noun phrase describing the data  Data store— noun phrase naming the file, database, or repository where the system keeps data  Process— verb phrase describing the operation done on the data. Processes may be labeled with the name of a system or operation that manipulates the data
  • 14. 14 Abdisalam Issa-Salwe, Thames Valley University 27 Data flow diagrams (DFDs) (cont…)  Data Flow Diagramming Rules  Processes cannot have only outputs, cannot have only inputs, and must have a verb phrase label.  Data can only move to a data store from a process, not from another data store or an outside source.  Similarly, data can only be moved to an outside sink or to another data store by a process.  Data to and from external sources and sinks can only be moved by processes.  Data flows move in one direction only.  Both branches of a forked or a joined data flowmust represent the same type of data.  A data flow cannot return to the process from which it originated. Abdisalam Issa-Salwe, Thames Valley University 28
  • 15. 15 Abdisalam Issa-Salwe, Thames Valley University 29 Abdisalam Issa-Salwe, Thames Valley University 30 Flowcharts  The flowchart is a means of visually presenting the flow of data through an information processing systems  The operations performed within the system and the sequence in which they are performed
  • 16. 16 Abdisalam Issa-Salwe, Thames Valley University 31 Flowcharts (cont…)  A diagram that uses graphic  symbols to depict the nature  and flow of the steps in a  process. Abdisalam Issa-Salwe, Thames Valley University 32 Start or end of the program Computational steps or processing function of a program Input or output operation Decision making and branching Connector or joining of two parts of program Magnetic Disk Magnetic Disk Off-page connector Flow line Annotation Display
  • 17. 17 Abdisalam Issa-Salwe, Thames Valley University 33 Guidelines in Flowcharting  The following are some guidelines in flowcharting: a. In drawing a proper flowchart, all necessary requirements should be listed out in logical order. b. The flowchart should be clear, neat and easy to follow. There should not be any room for ambiguity in understanding the flowchart. c. The usual direction of the flow of a procedure or system is from left to right or top to bottom.  Only one flow line should come out from a process symbol. Abdisalam Issa-Salwe, Thames Valley University 34 Only one flow line should enter a decision symbol, but two or three flow lines, one for each possible answer, should leave the decision symbol. a.Only one flow line should come out from a process symbol
  • 18. 18 Abdisalam Issa-Salwe, Thames Valley University 35 Only one flow line is used in conjunction with terminal symbol Abdisalam Issa-Salwe, Thames Valley University 36 Flowcharts (cont…)  Benefits of Using Flowcharts  Promote process understanding  Provide tool for training  Identify problem areas and improvement opportunities  Depict customer-supplier relationships
  • 19. 19 Abdisalam Issa-Salwe, Thames Valley University 37 Abdisalam Issa-Salwe, Thames Valley University 38
  • 20. 20 Abdisalam Issa-Salwe, Thames Valley University 39 Flowcharts (cont…)  How do we interpret our Flowcharts?  A Flowchart will help you understand your process and uncover ways to improve it only if you use it to analyze what is happening. Interpreting your Flowchart will help you to:  Determine who is involved in the process.  Form theories about root causes.  Identify ways to streamline the process.  Determine how to implement changes to the process.  Locate cost-added-only steps.  Provide training on how the process works or should work.

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