Chapter 3 – Requirements Modeling Flashcards
System Analysis Activities
Requirements modeling (fact finding) • Output: - Electronic/printed information produced by the system • Input: - Data entered into the system ~ Manually ~ Automated • Processes: - Logical rules applied ~ Transform the data into meaningful information • Performance: - System characteristics: ~ Speed ~ Volume ~ Capacity ~ Availability ~ Reliability • Security: - Hardware, software and procedural controls ~ Safeguards and protect the system and its data from internal or external threats
Modeling Tools and Techniques
- CASE Tools
- Functional Decomposition Diagram (FDD)
- Data Flow Diagrams (DFD)
- Unified Modeling Language (UM Language)
CASE Tools
- Offer powerful modeling features
* Systems analyst use modeling and fact-finding interactively
Functional Decomposition Diagram (FDD)
Structure charts
Data Flow Diagrams (DFD)
Shows how the system: • Stores • Processes • Transforms -Data
Unified Modeling Language (UM Language)
• Widely used method of visualizing and documenting software systems design
• Use case diagrams
- Actor
• Sequence diagrams
System requirement
• Characteristic or feature
- Must be included in an information system
~ To satisfy business requirements
~ Be acceptable to users
Systems Requirements Checklist
Five general categories: • Outputs • Inputs • Processes • Performance • Controls
Outputs
- Website – Report online volume statistics every 4 hours
* Inventory system – Produce a daily report showing part number, description, quantity on hand, etc.
Inputs
- Manufacturing employees – Swipe their ID card into online data collection terminals (record labor costs, calculate production efficiency)
- Department head – Enter overtime hours
Processes
- Student records system – Calculate GPA at the end of each semester
- Payroll system – Update employee salaries, bonuses and benefits, and produce tax data
Performance
- System – Support 25 users online simultaneously
* Response time – Not exceed 4 seconds
Controls
- System – Provide logon security (at operating system level & application level)
- Employee record – Added, changed or deleted (only by a member of human resources department)
Future Growth, Costs and Benefits (*)
- Scalability
* Total cost of ownership (TCO)
Scalability
• System’s ability to: - Handle increased business volume - Transactions in the future • Scalable system: - Offers a better return ~ On the initial investment • To evaluate scalability: - Requires information about projected future volume for all: ~ Outputs ~ Inputs ~ Processes
Total Cost of Ownership (TCO)
• System developers:
- Identify
- Document
~ Indirect expenses (other than direct costs)
• That contributes to the total cost of ownership
• Especially important if:
- The development team is evaluating several alternatives
• Problem:
- Cost estimates tend to understate indirect costs
Direct costs
• Spent on products • Expenses used in: - The creation of the products - Examples: ~ Costs of materials to produce the product ~ Equipment, labour costs
Indirect costs
• Do not spend on a product • Expenses needed for: - Operating the company • Examples: - Cleaning supplies - Office equipment
Fact-Finding
• Fact-Finding Overview
- Identify the information needed
- Develop a fact-finding plan
• Who, What, Where, When, How, and Why?
- Difference between asking:
~ What is being done (Now) – Current System
~ What could or should be done (Future) – Proposed System
Fact Finding Techniques
- Interviews
- Document Review
- Observation
- Questionnaire
- Surveys
- Research
- Site Visits
Interviews
• Seven steps
• Step 1: Determine the People to Interview - Formal structure ~ From organization chart - Informal structure ~ Based on interpersonal relationships
• Step 2: Establish Objectives for the Interview
- General areas to be discussed - Lists the facts you want to gather
• Step 3: Develop Interview Questions
- Create standard list of interview questions helps keep you on track
- Avoid leading questions leads to only a single direction/answer
~ Example:
+ What advantages do you see in the proposed system?
- Avoid open-ended questions:
~ Anything can be an answer (no fixed/standard answer)
~ Example:
+ How is this task performed?
- Avoid close-ended questions there is a fixed/standard answer
~ Examples:
+ How many computers do you have in this department?
- Avoid range-of-response questions
~ Scaling answer
~ Example:
+ On a scale of 1 to 10, with 1 the lowest and 10 the highest, how effective was your training?
• Step 4: Prepare for the Interview - Careful preparation is essential ~ Interview is an important meeting - Limit the interview time ~ No more than 1 hour - Send a list of topics - Ask the interviewee to have samples available
• Step 5: Conduct the Interview - Develop a specific plan (for the meeting) - Begin: ~ Introducing yourself ~ Describe the project ~ Explain the interview objectives - Engaged listening - Allow the person enough time to think about the question - After an interview: ~ Summarize the session ~ Seek a confirmation
• Step 6: Document the Interview - Note taking: ~ Kept to a minimum - After conducting the interview: ~ Record the information quickly - After the interview: ~ Send memo to the interviewee expressing your appreciation - Note: ~ Data ~ Time ~ Location ~ Purpose of the interview ~ Main points discussed \+ so the interviewee has a written summary and can offer additions or corrections.
• Step 7: Evaluate the Interview
- Identify any possible biases
- Example:
~ Give incomplete answers
~ Refrain from volunteering information
~ Strong opinions about the current or future system might distort the facts
~ Answers questions in an attempt to be helpful but do not have the necessary experience to provide accurate information
• Unsuccessful Interviews
- Some are not successful
~ No matter how well prepared you are for interviews
Interview Summary
- Determine the people (1)
- Establish objectives (2)
- Develop interview questions (3)
- Prepare (4)
- Conduct (5)
- Document (6)
- Evaluate (7)
Other Fact-Finding Techniques
- Document Review
- Observation
- Questionnaires and Surveys
- Sampling
- Research
- Interviews versus Questionnaires
Document Review
All paper & documents must be analyzed
Observation
o Seeing the system in action Gives additional perspective Better understanding of the system procedures o Plan observations in advance o Hawthorne Effect
Questionnaires and Surveys
o Most important rule of all:
Make sure that the questions collect the right data
• In a form that can be used to further his/her fact-finding
Fill-in-form
Sampling
o List of 200 customers – representative sample of 20 customers
o Systematic sample
Interview every 10th customer
o Stratified sample
Geographical
Choose 5 customers from each of 4 postal codes
o Random sample
Choose any 20 customers
o Main objective:
Ensure that it represents the overall population accurately
Research
• Includes: ~ Internet ~ IT magazines ~ Books - To obtain: ~ Background information ~ Technical material ~ News - About industry trends and developments
• Site visit
- Going to a location or visiting
Interviews versus Questionnaires
• Interview: - More familiar - Personal • Questionnaire: - Gives many people the opportunity to: ~ Provide input ~ Provide suggestions • Brainstorming - Structured: ~ Take turns to give ideas - Unstructured: ~ Anyone can give ideas anytime
Documentation
• The Need for Recording the Facts - Record information ~ As soon as it is obtained - Use the simplest recording method - Record your findings in such a way that: ~ They can be understood by someone else - Organize documentation ~ Related material can be located easily • Software Tools - CASE Tools - Productivity Software ~ Word processing ~ Spreadsheets ~ Database management ~ Presentation graphics program ~ Histogram - Graphics modeling software - Personal information managers ~ Personal information manager (PIM) ~ Handheld computers ~ Personal digital assistants (PDAs) - Wireless communication devices
Preview of Logical Modeling
• Systems developers:
- Have a clear understanding of business processes and system requirements
• Construct a logical model of the system
Overview of Data and Process Modeling Tools
• Data Flow Diagrams (DFD)
- Uses various symbols
~ Shows how the system transforms input data into useful information
Data Flow Diagrams (*)
• Shows:
- How data moves through an information system
~ Does not show program logic or processing steps
- WHAT the system does
~ Not HOW it does it
Data Dictionary / Data Repository (*)
• Central storehouse of information - About the system’s data • Used by an analyst to: - Collect - Document - Organize ~ Specific facts about the system • Defines and describes: - All data elements - Meaningful combinations of data elements • Data element / Data item / Field: - Smallest piece of data ~ That has meaning - Combined into records ~ Also called data structures • Record: - Meaningful combination of related elements ~ That is included in a data flow Or ~ Retained in a data store
Process Description Tools
• Process description:
- Documents the details of a function primitive
~ Represents a specific set of processing steps and business logic
• Can also be used in object-oriented development
• Modular design
• Combinations of 3 logical structures / control structures
- Serve as building blocks for the process
~ Sequence (1)
~ Selection (2)
~ Iteration-looping (3)
• Structured English()
• Decision Tables()
• Decision Trees
Structured English(*)
• Must conform to the following rules: - Use only the three blocks of: ~ Sequence ~ Selection ~ Iteration • Indentation: - For readability • Use a limited vocabulary including: - Standard terms used in the data dictionary - Specific words that describe the processing rules • Resembles pseudocode • Primary purpose: - Describe the underlying business logic
Decision Tables(*)
• Shows logical structure with:
- All possible combinations of conditions
- Resulting actions
• Important to consider every possible outcome:
- Ensure nothing is overlooked
Decision Trees
• Graphical representation of: ~ Conditions ~ Actions ~ Rules - Found in a decision table • An effective way - To describe a relatively simple process
Logical vs Physical Models
- Structured analysis tools
- Physical model
- Sequence of Models
- Four-Model Approach
Structured analysis tools
• Used to:
- Develop a logical model for a new information system
• Can also be used to:
- Develop physical models of an information system
Physical model
Shows how the system’s requirements are implemented
Sequence of Models
• System analysts:
- Create a physical model of the current system (1st step)
- Develop a logical model of the current system (2nd step)
- Tackling logical model of the new system (3rd step)
• Allows them to:
- Understand the current system better
Four-Model Approach
• Develop a: - Physical model of the current system - Logical model of the current system - Logical model of the new system - Physical model of the new system • Disadvantage: - Added time - Added cost
