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System Engineering

College of Engineering and Computer Science Computer Science Department CSC 131 Computer Software Engineering Fall 2006 Lecture # 2 Chapter 6 & 7 System Engineering & Requirements Engineering. System Engineering. Before SW can be engineered, the system and its envoriment must be understood.

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System Engineering

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  1. College of Engineering and Computer ScienceComputer Science DepartmentCSC 131Computer Software EngineeringFall 2006 Lecture # 2Chapter 6 & 7System Engineering & Requirements Engineering

  2. System Engineering • Before SW can be engineered, the system and its envoriment must be understood. • To accomplish this : • Overall objectives of the system must be determined • The role of HW, SW, people, procedures must be identified… • Operational requirements must be elicited, analyzed, specified, modeled, validated, and managed.

  3. System Engineering – Two Views • Business Process Engineering • Focuses on utilizing IT effectively • Product Engineering • Focuses on converting the customer’s needs into a working/functional product

  4. System Engineering • Concentrate not only on the software but rather on the system as a whole and its elements… • SE occurs as a result of a process called system engineering.

  5. System Modeling • Model the system • Easier to asses the system • Easier to evaluate system components in relationship to one another • More on system modeling later….

  6. System Context Diagram (SCD) • It establishes the information boundary between the system being implemented and environment in which the system operate. • It defines all external producers of information • It defines all external consumers of information

  7. Requirements Engineering • The outcome of the system engineering process is the specification of computer-based system at the different levels.

  8. Requirements Engineering • Requirements engineering process can be described in seven steps: • Inception • Requirement Elicitation • Requirement Elaboration • Requirement Analysis & Negotiation • Requirement Specification • Requirement Validation • Requirement Management

  9. Requirements? • Definition “A feature of the system or a description of something the system is capable of doing in order to fulfill the system’s purpose” • Types of Requirements • Functional • Non-functional • Strengths • Must/Shall • Should • Will

  10. Requirements Elicitation • Why requirement elicitation is difficult? • Problem of scope • The boundary of the system is ill-defined • Problem of understanding • Customers are not sure of what is needed • Problem of volatility • Requirements change over time.

  11. Requirements Elicitation • Techniques • Interview / Meeting • Survey / Questionnaire • Observations • Temporary Assignment • Business Plans • Review Internal / External Documents • Review Software

  12. Elaboration • The information obtained in the elicitation step is expanded and refined • Develop a refined model

  13. Requirements Analysis & Negotiation Once requirements have been gathered then .. • Categorize requirements • Organize requirements into related subsets • Establish requirements relationships • Examine requirements consistency • Rank requirements based on the need of customers.

  14. Questions That Must Be Asked… • Is each requirement consistent with the objective? • Have all requirements been specified? • Is each requirement really necessary? • Is each requirement clear? • Is each requirement testable? • …….

  15. Requirements Specification • System Specification is the final product of system and requirements engineering. • It serves as the foundation for HW, SW engineering • It describes the function and performance of a system/product and its constraints

  16. Requirements Specification… • A specification can be: • A written document • A graphical model • A formal mathematical model • A prototype • Any combination of the above …

  17. Requirements Validation • Why requirements validation? • To Ensure the following: • All system requirements have been stated clearly • Inconsistencies, errors, omissions have been detected and corrected • Product conforms to the standards • Mainly done by Formal Technical Review Team

  18. Requirements Management • It is a set of activities that support the project team to: • Identify , control, and track requirements and changes to requirements at any time. • Why requirement management?? • Because requirements change…

  19. Requirements Review? • Are the requirements complete? • Are the requirements concise? • Are the requirements correct? • Are the requirements consistent? • Are the requirements modular? Can they accommodate change? • Are the requirements realistic? • Are the requirements needed by the customer? • Are the requirements traceable?

  20. Questions ..?

  21. What is next? • Deliverable # 1 due • Assignment # 1

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