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Investigating user requirements Process models (DFD and Flowcharts)
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SYSTEMS ANALYSIS USER REQUIREMENTS
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Lecture 12
Abdisalam Issa-Salwe
Thames Valley University
Abdisalam Issa-Salwe, Thames Valley University
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Topic list
Investigating user requirements
Process models (DFD and Flowcharts)
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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
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Systems Investigation
Techniques used in gathering information to investigate the
present system include:
Interviews
Questionnaires
Observation and inspection of records
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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.
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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
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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
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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
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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
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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.
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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.
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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.
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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
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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)
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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)
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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
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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?
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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
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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.
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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.
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DFD Notation
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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
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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.
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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
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Flowcharts (cont…)
A diagram that uses graphic
symbols to depict the nature
and flow of the steps in a
process.
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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
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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.
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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
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Only one flow line is used in conjunction
with terminal symbol
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Flowcharts (cont…)
Benefits of Using Flowcharts
Promote process understanding
Provide tool for training
Identify problem areas and improvement opportunities
Depict customer-supplier relationships
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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.