WXGE 6103 Software Engineering Process and Practice System

WXGE 6103 Software Engineering Process and Practice System Engineering

Overview Purposeful collection of interrelated components that work together to achieve certain objective (DEFINITION) System (CATEGORIES) Technical Computer-based System Socio Technical System Emergent Properties Non. Deterministic Complex relationship with organizational objective

Overview System Engineering Process System Requirements Definition 1 System Decommission 8 7 System Evolution 2 System Engineering 3 (activity of specifying, designing, implementing, validating, deploying and maintaining socio-technical systems) 4 6 System Integration System Design 5 Sub-system development System Modeling

System Engineering Process

System Requirements Definition n n Def : specify what the system should do (its functions) and its essential and desirable system properties. Who involve : stakeholders ¨ developers ¨ end-users ¨ n Types of requirement : Abstract functional requirement ¨ System properties (non-functional) ¨ Characteristic that system must not exhibit ¨

System Design n Def : Graphical presentation of how the system functionalities is to be provided by the system components

System Design Figure : The system design process

System Design Figure : A spiral model of requirements and design

System Modeling n n Def : An architectural model presents an abstract view of the subsystems making up a system. May include major information flows between sub-systems. Usually presented as a block diagram. May identify different types of functional component in the model.

System Modeling Example : A simple burglar alarm system architecture

Sub-system development n n n Sub-systems identified during system design are implemented. (from scratch or COTS) Typically sub-systems are developed in parallel. Lack of communication across implementation teams. Usually involve software changes- during problem occurs Slow mechanism for proposing system changes means that the development schedule may be extended because of the need for rework.

System Integration ¨ During this phase, you take the independently developed sub-systems and put them together to make up a complete system. ¨ The process of putting hardware, software and people together to make a system. ¨ Should be tackled incrementally so that sub-systems are integrated one at a time. ¨ Interface problems between sub-systems are usually found at this stage. ¨ May be problems with uncoordinated deliveries of system components.

System Evolution Large systems have a long lifetime. They must evolve to meet changing requirements. ¨ Evolution is inherently costly n Changes must be analysed from a technical and business perspective n Sub-systems interact so unanticipated problems can arise n There is rarely a rationale for original design decisions n System structure is corrupted as changes are made to it ¨ Existing systems which must be maintained are sometimes called legacy systems. ¨

System Decommission ¨ Taking the system out of service after its useful lifetime ¨ May require removal of materials which pollute the environment. ¨ May require data to be restructured and converted to be used in some other system