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CHAPTER 3 : SYSTEM ANALYSIS - Coggle Diagram
CHAPTER 3 : SYSTEM ANALYSIS
3.1 PRELIMINARY ANALYSIS
System requirements
during requirements modeling, systems developers must identify and describe all system requirements
a system requrements is a characteristic or feature that must be included in an information system requirements
fall into five general categories:
outputs
inputs
processes
performance
controls
Fact finding techniques
must identify the information you need
Develop a fact-finding plan, which can involve series of questions (4W1H), or use a more structured approach such as the Zachman Frameworkd
i. (Who?) Who performs each of the procedures within the system? Why? Are the correct people performing the activity? Could other people perform the tasks more effectively?
ii. (What?)What is being done? What procedures are being followed? Why is that process necessary? Often, procedures are followed for many years and no one knows why. You should question why a procedure is being followed at all.
ii. (Where?) Where are operations being performed? Why? Where could they be performed? Could they be performed more efficiently elsewhere?
iv. (When?) When is a procedure performed? Why is it being performed at this time? Is this the best time?
v. (How?)How is a procedure performed? Why is it performed in that manner? Could it be performed
The Zachman Framework. Zachman Framework for Enterprise Architecture
The techniques used in fact finding :
Interviews
Step 1 : Determine the people to interview.
Step 2 : Establish objectives for the interview.
Step 3 : Develop interview questions.
Step 4 : Prepare for the interview.
Step 5 : Conduct the interview.
Step 6 : Document the interview.
Step 7 : Evaluate the interview
Documentation review
Document review can help you understand how the current system is supposed to work
Remember that system documentation sometimes is out of date. Forms can change or be discontinued, and documented procedures often are modified or eliminated.
You should obtain copies of actual forms and operating documents currently in use. You also should review blank copies of forms, as well as samples of actual completed forms.
Observations
Seeing the system in action gives you additional perspective and a better understanding of the system procedures
Personal observation also allows you to verify statements made in interviews and determine whether procedures really operate as they are described
Questionnaires
In projects where it is desirable to obtain input from a large number of people, a questionnaire can be a valuable tool.
A questionnaire, also called a survey, is a document containing a number of standard questions that can be sent to many individuals
Sampling
The samples might include records, reports, operational logs, data entry documents, complaint summaries, work requests, and various types of forms.
Sampling techniques include;
Systematic sampling
Stratified sampling
Random sampling
Research
Research is another important fact-finding technique.
Your research can include the Internet, IT magazines, and books to obtain background information, technical material, and news about industry trends and developments.
Use appropriate fact-finding technique
interview
benefit
Information comes directly from knowledgeable people in the community
Allows for exploration of unexpected information
Can be easily combined with other data gathering techniques
limitation
Not efficient for reaching a large number of people
Must select the right informant
Informant may have biased
Documentation review / Sampling
BENEFIT
Can take less time and cost than other approaches
Avoids duplication of data
Can offer information not available through other techniques.
LIMITATIONS
The data can be outdated
The scope of the information you gather will be limited to what has already been gathered
Data rarely come directly from the population you are trying to assess
Observations
BENEFIT
Useful for collecting information in settings where interviews may not be feasible
Less invasive than other methods
LIMITATION
Limited to activities that can be observed; lacks direct insight about the observed perceptions.
Not efficient method for obtaining quantitative data
Questionnaires
BENEFIT
Questions format are carefully created ahead of time, taking into consideration literacy level and language preferences of target population.
Less sensitive to biases introduced by interviewers
LIMITATIONS
Risk of a poor return rate, as respondents may choose not to mail the survey back.
Surveyor cannot control who actually responds to the survey
Research
BENEFIT
System analyst is able to obtain a vast amount of up-to-date information from all around the world.
LIMITATIONS
May not be suitable or applicable to the current system
Analyze the gathered information
Step 1 : Review the questions
Step 2 : Organize the information
Step 3 : Decide how to analyze the information
Step 4 : Analyze quantitative information
Step 5 : Analyze qualitative information
Step 6 : Integrate the information
modeling tools and teqniques
Involves graphical methods and nontechnical language that represent the system at various stages of development
To help them understand system requirements, analysts use
Functional Decomposition Diagrams (FDD)
Unified Modeling Language (UML) diagrams.
functional decomposition diagrams
Using an FDD, an analyst can show business functions and break them down into lower-level functions and processes.
A functional decomposition diagram (FDD) is a top-down representation of a function or process.
FDDs can be used at several stages of systems development
unified modeling language
The Unified Modeling Language (UML) is a widely used method of visualizing and documenting software systems design
UML provides various graphical tools, such as ;
use case diagrams
sequence diagrams.
3.2 DATA & PROCESS MODELLING
Data & process modelling concepts
Systems analysts use many graphical techniques to describe an information system
A data flow diagram (DFD) uses various symbols to show how the system transforms input data into useful information.
Data flow Diagram
A data flow diagram (DFD) shows how data moves through an information system but does not show program logic or processing steps( flow of data between process).
A set of DFDs provides a logical model that shows what the system does, not how it does it
Data diztionary
A data dictionary, or data repository, is a central storehouse of information about the system’s data
An analyst uses the data dictionary to collect, document, and organize specific facts about the system
Data elements are combined into records, also called data structures
Process description
A process description documents the details of a functional primitive, which represents a specific set of processing steps and business logic
Process specification
Decision Table
Structured English
Modular design
Logical & physical model
While structured analysis tools are used to develop a logical model for a new information system, such tools also can be used to develop physical models of an information system
A physical model shows how the system’s requirements are implemented