Software Requirements Software Engineering Software Engineering Software Engineering

Requirements engineering processes l l l The goal of the REP is to create

The requirements engineering process Software Engineering

Requirements discovery l l The process of gathering information about the proposed and existing

ATM stakeholders l l l l l Bank customers Representatives of other banks Bank

Requirements validation l l Concerned with demonstrating that the requirements define the system that

Requirements checking l l l Validity. Does the system provide the functions which best

Requirements validation techniques l Requirements reviews • l Prototyping • l Systematic manual analysis

Requirements management l l Requirements management is the process of managing changing requirements during

Requirements change l l l The priority of requirements from different viewpoints changes during

Requirements evolution Software Engineering

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Software Requirements Software Engineering

Software Engineering

Requirements engineering processes l l l The goal of the REP is to create and maintain a system requirements document The processes used for RE vary widely depending on the application domain, the people involved and the organisation developing the requirements. However, there a number of generic activities common to all processes • • Requirements elicitation; Requirements analysis; Requirements validation; Requirements management. Software Engineering

Software Engineering

The requirements engineering process Software Engineering

Software Engineering

Requirements discovery l l The process of gathering information about the proposed and existing systems and distilling the user and system requirements from this information. Sources of information include: • • • l documentation system stakeholders and the specifications of similar systems. Techniques required to help the discovery: • • • Interviews Observation Scenarios and prototypes Software Engineering

Software Engineering

ATM stakeholders l l l l l Bank customers Representatives of other banks Bank managers Counter staff Database administrators Security managers Marketing department Hardware and software maintenance engineers Banking regulators Software Engineering

Requirements validation l l Concerned with demonstrating that the requirements define the system that the customer really wants. Requirements error costs are high so validation is very important • Fixing a requirements error after delivery may cost up to 100 times the cost of fixing an implementation error. Software Engineering

Requirements checking l l l Validity. Does the system provide the functions which best support the customer’s needs? Consistency. Are there any requirements conflicts? Completeness. Are all functions required by the customer included? Realism. Can the requirements be implemented given available budget and technology Verifiability. Can the requirements be checked? Software Engineering

Requirements validation techniques l Requirements reviews • l Prototyping • l Systematic manual analysis of the requirements. Using an executable model of the system to check requirements. Test-case generation • Developing tests for requirements to check testability. Software Engineering

Requirements management l l Requirements management is the process of managing changing requirements during the requirements engineering process and system development. Requirements are inevitably incomplete and inconsistent • • New requirements emerge during the process as business needs change and a better understanding of the system is developed; Different viewpoints have different requirements and these are often contradictory. Software Engineering

Requirements change l l l The priority of requirements from different viewpoints changes during the development process. System customers may specify requirements from a business perspective that conflict with end-user requirements. The business and technical environment of the system changes during its development. Software Engineering

Requirements evolution Software Engineering

Software Engineering