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CHAPTER 3 : SYSTEM ANALYSIS : - Coggle Diagram
CHAPTER 3 : SYSTEM ANALYSIS :
3.1 Preliminary Analysis
5 Categories System requirements
Processes
The student records system must calculate the GPA at the end of each semester.
Performance
The system must support 25 users online simultaneously.
Inputs
Each input form must include date, time, product code, customer number, and quantity.
Controls
The system must provide logon security at the operating system level and at the application level
Outputs
The Web site must report online volume statistics every four hours, and hourly during peak periods.
3.2 Data and Process Modelling
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).
DFD Symbols
Data flow symbol
Data flow symbol
Process symbol
Data store symbol
Entity Symbol
Creating a set of DFD
Step 1 : Draw a context diagram
Step 2: Draw a Diagram 0 DFD
Step 3: Draw the Lower-Level Diagrams
Fact Finding Techniques
Series of questions (4W1H)
Who
Who performs each of the procedures within the system?
What
What is being done?
Where
Where are operations being performed?
When
When is a procedure performed?
How
How is a procedure performed?
6 Fact Finding Techniques
Interviews
An interview is a planned meeting during which you obtain information from another person.
7 Steps for each interview:
Step 3 : Develop interview questions
Step 4 : Prepare for the interview.
Step 2 : Establish objectives for the interview.
Step 5 : Conduct the interview.
Step 1 : Determine the people to interview.
Step 6 : Document the interview.
Step 7 : Evaluate the interview.
Observations
Plan your observations in advance by preparing a checklist of specific tasks you want to observe and questions you want to ask
Documentation review
Document review can help you understand how the current system is supposed to work
Questionnaires
Document containing a number of standard questions that can be sent to many individuals
2 Types of questions
Open-ended questions
That require more than one word answers.
The answers could come in the form of a list, a few sentences or something longer such as a speech, or essay.
For example : What is the method used to record data previously?
Close-ended questions
It consists of questions that are used when the systems analyst effectively lists all possible responses, which are mutually exclusive.
Sampling
Main objective of a sample is to ensure that it represents the overall population accurately.
3 Sampling techniques include
Systematic sampling
A systematic sample would select every tenth customer for review
Stratified sampling
select a certain percentage of transactions from each zip code, rather than a fixed number.
Random sampling
A random sample selects any 20 customers
Research
Research also can involve a visit to a physical location, called a site visit, where the objective is to observe a system in use at another location.
6 Steps Analyze The Gathered Information
Step 3 : Decide how to analyze the information
Analysis of parts may be simply adding up numbers and averaging them or comparing information to examine the relationship of one thing to another, or two things together.
Step 4 : Analyze quantitative information
Quantitative (numbers) information will be computed by hand, or with the use of adding machines
Step 2 : Organize the information
There is a certain logic that can be followed.
Step 1 : Review the questions
The questions generated before the information was gathered should be reviewed.
Step 5 : Analyze qualitative information
Analysis of qualitative (descriptive) information is a creative and critical process.
Step 6 : Integrate the information
Putting the analyzed parts together in a way that tells the complete story can be done by the team that has been assigned to gather and analyze information.
Modeling Tools and Techniques
Modeling Tools and Techniques
System requirements, analysts use
Functional Decomposition Diagrams (FDD)
Top-down representation of a function or process.
Unified Modeling Language (UML) diagrams.
widely used method of visualizing and documenting software systems design
UML provides various graphical tools
use case diagrams
represents the interaction between users and the information system.
sequence diagrams.
shows the timing of interactions between objects as they occur
4 symbols that represent
Lifelines
Messages
Focuses
Classes
DATA DICTIONARY
or data repository, is a central storehouse of information about the system’s data
Documenting the Data Elements
Alias
Type and length
Data element name and label
Default value
Acceptable values - Domain and validity rules
Source
Security
Responsible user(s)
Description and comments
Documenting the Data Flows
Description
Alternate name(s)
Data flow name or label
Origin
Record
Destination
Volume and frequency
Documenting the Data Stores
Alternate name(s)
Attributes
Description
Volume and frequency
Data store name or label
Documenting the processes
Description
Process number
Process name or label
Process description
Documenting the Entities
Alternate name(s)
Input data flows
Description
Output data flows
Entity name
Documenting the records
Definition or description
Alternate name(s)
Record or data structure name
Attributes
Process Description
Documents the details of a functional primitive , which represents a specific set of processing steps and business logic
3 Process specification
Modular design
Based on combinations of three logical structures which serve as building blocks for process
3 structures
Sequence
Selection
Iteration
Structured english
Decision table
Structure english
3 following rules
Use identation for readability
Use a limited vocabulary , including standard terms used in the data dictionary and specific words that describe the processing rules
Use only 3 building blocks of sequence , selection or iteration
Decision tables
Shows a logical structure , will a possible combination of conditions and resulting actions
4 types of tables
Tables with one condition
Tables with two condition
Tables with three condition
Tables with multiple outcomes
Decision tree
Graphical representation of the conditions , actions , and rules found in a decision table
Logical and 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
Sequence of models
Performing that extra step allows them to understand the current system better
