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SYSTEM ANALYSIS - Coggle Diagram

- - - - The Web site must report online volume statistics every four hours, and hourly during peak periods.
    - - Manufacturing employees must swipe their ID cards into online data collection terminals that record labor costs and calculate production efficiency.
    - - The student records system must calculate the GPA at the end of each semester.
    - - The system must support 25 users online simultaneously.
    - - The system must provide logon security at the operating system level and at the application level.
  - - - 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?
    - - 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.
    - - Where are operations being performed? Why? Where could they be performed? Could they be performed more efficiently elsewhere?
    - - When is a procedure performed? Why is it being performed at this time? Is this the best time?
    - - How is a procedure performed? Why is it performed in that manner? Could it be performed
    - - Interviews
        
        Interviewing is an important fact-finding tool during the systems analysis phase. An interview is a planned meeting during which you obtain information from another person.
        
        benefit
        
        allow for exploration of unexpected information.
        
        limitations
        
        must select the right informant.
        
        Documentation review
        
        Document review can help you understand how the current system is supposed to work.
        
        benefit
        
        avoid duplication of data
        
        limitations
        
        the data can be outdate.
        
        Observations
        
        Seeing the system in action gives you additional perspective and a better understanding of the system procedures
        
        benefit
        
        less invavise than other methods.
        
        limitations
        
        not efficient method for obtaining quantitative data.
        
        Questionnaires
        
        In projects where it is desirable to obtain input from a large number of people, a questionnaire can be a valuable tool.
        
        benefit
        
        less sensitive to biases introduced by interviewers.
        
        limititations
        
        surveyor cannot control who actually responds to the survey.
        
        Sampling
        
        When studying an information system, you should collect examples of actual documents using a process called sampling.
        
        The samples might include records, reports, operational logs, data entry documents, complaint summaries, work requests, and various types of forms.
        
        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.
        
        Site visits also are important when considering the purchase of a software package.
        
        benefit
        
        able to exchange opinions and thoughts through the internet.
        
        may not be suitable or application to current system.
  - - - Step 1 : Review the questions
        
        The questions generated before the information was gathered should be reviewed.
        
        Step 2 : Organize the information
        
        Gather together all relevant information that has been collected.
        
        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
        
        It is likely that quantitative (numbers) information will be computed by hand, or with the use of adding machines.
        
        Step 5 : Analyze qualitative information
        
        -Analysis of qualitative (descriptive) information is a creative and critical process.
        -The way the information has been gathered will probably determine how it can be analyzed.
        
        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.
  - - - sequence diagrams.
        
        A sequence diagram shows the timing of interactions between objects as they occur.
        
        A systems analyst might use a sequence diagram to show all possible outcomes, or focus on a single scenario.
      - use case diagrams
        
        During requirements modeling, systems analysts and users work together to document requirements and model system functions.
        
        A use case diagram visually represents the interaction between users and the information system.
- - - - Avoid;
        
        Spontaneous generation = process produces output, but has no input data flow
        
        Black hole = process that has input, but produces no output
        
        Gray hole = process that has at least one input and one output, but the data obviously is insufficient to generate the output
    - - Represent data that the system stores
        
        The physical characteristics of a data store are unimportant because you are concerned only with a logical model
  - - - Draw the context diagram so that it fits on one page
        
        Use the name of the information system as the process name in the context diagram
        
        Use unique names within each set of symbols
        
        Do not cross lines
        
        Provide a unique name and reference number for each process
        
        Obtain as much user input and feedback as possible
  - - - The following attributes:
        
        Data element name and label
        
        Alias
        
        Type and length
        
        Default value
        
        Acceptable values - Domain and validity rules
        
        Source
        
        Security
        
        Responsible user(s)
        
        Description and comments
        :
      - typical attributes :
        
        Data flow name or label
        
        Description
        
        Alternate name(s)
        
        Origin
        
        Destination
        
        Record
        
        Volume and frequency
      - Typical characteristics data store
        
        Data store name or label
        
        Description
        
        Alternate name(s)
        
        Attributes
        
        Volume and frequency
      - Typical characteristics of a process
        
        Process name or label
        
        Description
        
        Process number
        
        Process description
      - Typical characteristics of an entity include
        
        Entity name
        
        Description
        
        Alternate name(s)
        
        Input data flows
        
        Output data flows
      - Typical characteristics of a record include
        
        Record or data structure name
        
        Definition or description
        
        Alternate name(s)
        
        Attributes
- - - - Modular design
        
        Modular design is based on combinations of three logical structures, sometimes called control structures, which serve as building blocks for the process.
        Three structures are called
        
        sequence
        
        selection
        
        iteration
        
        Symbol
        
        A rectangle represents a step or process
        
        Sequence
        
        The completion of steps in sequential order, one after another.
        
        Selection
        
        The completion of one of two or more process steps based on the results of a test or condition.
        
        Iteration
        
        The completion of a process step that is repeated until a specific condition changes.
      - Structured English
        
        Must conform to the following rules
        
        Use only the three building blocks of sequence, selection, and iteration
        
        Use indentation for readability
        
        Use a limited vocabulary, including standard terms used in the data dictionary and specific words that describe the processing rules
      - Decision Table
        
        Shows a logical structure, with all possible combinations of conditions and resulting actions
        
        It is important to consider every possible outcome to ensure that you have overlooked nothing
        
        Types of tables;
        
        Tables with one condition
        
        If a process has a single condition, there only are two possibilities – yes or no.
        
        Either the condition is present or it is not, so there are only two rules.
        
        Tables with two condition
        
        Suppose you want to create a decision table
        
        When documenting a process, it is important to ensure that you list every possibility.
        
        Tables with three condition
        
        Table with multiple outcomes
        
        In addition to multiple conditions, decision tables can have more than two possible outcomes.
        
        For example, the sales promotion policy includes three conditions:
        
        Was the customer a preferred customer
        
        Did the customer order $1,000 or more
        
        Did the customer use our company charge card
        
        Decision tree
        
        A decision tree is a graphical representation of the conditions, actions, and rules found in a decision table.
        
        Decision trees show the logic structure in a horizontal form that resembles a tree with the roots at the left and the branches to the right.
        
        Like flowcharts, decision trees are useful ways to present the system to management.
        
        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
        
        Sequence of Models
        
        Many systems analysts create a physical model of the current system and then develop a logical model of the current system before tackling a logical model of the new system
        
        Performing that extra step allows them to understand the current system better
        
        Four-Model Approach
        
        Develop a physical model of the current system, a logical model of the current system, a logical model of the new system, and a physical model of the new system.
        
        The only disadvantage of the four-model approach is the added time and cost