Computer System EngineeringCriteria for System Configuration: TechnicalCriteria for System Configuration: Business IssuesHardware and Hardware EngineeringHardware EngineeringSoftware and Software EngineeringThree high-level phases of Software EngineeringThird Phase of Software EngineeringStructured Design: Design IssuesDesign IssuesDesign HeuristicsDesign Heuristics (cont’d)Design PostprocessingDesign OptimizationSoftware Engineering CSE470: SySoftware Engineering CSE470: Systems Engineeringstems Engineering1Computer System EngineeringComputer System Engineering Computer System Engineering is a problem-solving activity. Itemize desired system functions Analyze them Allocate functions to individual system elements Systems Analyst (computer systems engineer) Start with customer-defined goals and constraints Derive a representation of function, performance, interfaces, design constraints, and information structure That can be allocated to each of the generic system elements (i.e., Software, Hardware, People, database, documentation, procedures) Focus on WHAT, NOT how.Software Engineering CSE470: SySoftware Engineering CSE470: Systems Engineeringstems Engineering2Criteria for System Configuration: TechnicalCriteria for System Configuration: TechnicalCriteria for allocation of function and performance to generic system elements: Technical Analysis: (existence of necessary technology, function and performance assured, maintainability) Environmental Interfaces: (proposed configuration integrate with external environment, interoperability) Off-the-shelf options must be considered. Manufacturing evaluation: (facilities and equipment available, quality assured?)Software Engineering CSE470: SySoftware Engineering CSE470: Systems Engineeringstems Engineering3Criteria for System Configuration: Business IssuesCriteria for System Configuration: Business IssuesCriteria for allocation of function and performance to generic system elements: Project_Considerations: (cost, schedules, and risks) Business_Considerations: (marketability, profitability) Legal_Considerations: (liability, proprietary issues, infringement?) Human issues: (personnel trained? political problems, customer understanding of problem)Software Engineering CSE470: SySoftware Engineering CSE470: Systems Engineeringstems Engineering4Hardware and Hardware EngineeringHardware and Hardware Engineering Characteristics: Components are packaged as individual building blocks Standardized interfaces among components Large number of off-the-shelf components Performance, cost, and availability easily determined/measured Hardware configuration built from a hierarchy of "building blocks."Software Engineering CSE470: SySoftware Engineering CSE470: Systems Engineeringstems Engineering5 Hardware Engineering Hardware EngineeringThree phases to system engineering of hardware: Development Planning and requirements analysis: best classes of hardware for problem, availability of hardware type of interface required identification of what needs to be designed and built Establish a Plan or "road map" for design implementation May involve a hardware specification. Use CAE/CAD to develop a prototype (breadboard) Develop printed circuit (PC) boards Manufacturing of boardsSoftware Engineering CSE470: SySoftware Engineering CSE470: Systems Engineeringstems Engineering6Software and Software EngineeringSoftware and Software EngineeringFunction may be the implementation of a sequential procedure for data manipulationPerformance may not be explicitly defined (exception is real-time systems)Software element of computer-based system consists of two classes of programs, data, and documentation Application_Software: implements the procedure that is required to accommodate information processing functions System Software: implements control functions that enable application software to interface with other system elementsSoftware Engineering CSE470: SySoftware Engineering CSE470: Systems Engineeringstems Engineering7Three high-level phases of Software EngineeringThree high-level phases of Software Engineering Definition phase: Software planning step Software Project Plan scope of project, risk, resource identification cost and schedule estimates Software Requirements Analysis Requirements Specification System element allocated to software is defined in detail. Formal information domain analysis to establish models of information flow and structure (expand to produce specification) Prototype of software is built and evaluated by customer Performance requirements or resource limits defined in terms of software characteristics Definition and Requirements must be performed in cooperationSoftware Engineering CSE470: SySoftware Engineering CSE470: Systems Engineeringstems Engineering8Third Phase of Software EngineeringThird Phase of Software EngineeringDevelopment Phase: Translate set of requirements into an operational system element Design Design Specification Coding (appropriate programming language or CASE tool) Should be able to directly trace detail design descriptions from code. Verification, release, and maintenance phase: Testing software to find maximum number of errors before shipping Testing plan Prepare software for release Quality Assurance Maintain software throughout its lifetimeSoftware Engineering CSE470: SySoftware Engineering CSE470: Systems Engineeringstems Engineering9Structured Design: Design IssuesStructured Design: Design IssuesModularity Criteria: Decomposability: decompose large problem into easier to solve subproblems Composability: how well modules can be reused to create other systems Understandability: how easily understood without other reference info Continuity: make small changes and have them reflected in corresponding changes in one or a few modules Protection: architectural characteristic to reduce propagation of side effects of a given error in a module.Software Engineering CSE470: SySoftware Engineering CSE470: Systems Engineeringstems Engineering10Design IssuesDesign IssuesBasic Design Principle:  Linguistic modular units: correspond to syntactic units in implementation language Few