SE_lec5.pdf

Software Processes Lecture 5 Chapter 2 Software Processes 1  Topics covered ✧ Software process models ✧ Process activities ✧ Coping with change ✧ The Rational Unified Process ▪ An example of a modern software process. Chapter 2 Software Processes 2  Pr...

Software Processes Lecture 5 Chapter 2 Software Processes 1  Topics covered ✧ Software process models ✧ Process activities ✧ Coping with change ✧ The Rational Unified Process ▪ An example of a modern software process. Chapter 2 Software Processes 2  Process activities ✧ Real software processes are interleaved sequences of technical, collaborative and managerial activities with the overall goal of specifying, designing, implementing and testing a software system. ✧ The four basic process activities of specification, development, validation and evolution are organized differently in different development processes. In the waterfall model, they are organized in sequence, whereas in incremental development they are interleaved. Chapter 2 Software Processes 3  Software specification ✧ The process of establishing what services are required and the constraints on the system’s operation and development. ✧ Requirements engineering process ▪ Feasibility study Is it technically and financially feasible to build the system? ▪ Requirements elicitation and analysis What do the system stakeholders require or expect from the system? ▪ Requirements specification Defining the requirements in detail ▪ Requirements validation Checking the validity of the requirements Chapter 2 Software Processes 4 The requirements engineering process Chapter 2 Software Processes 5  Software design and implementation ✧ The process of converting the system specification into an executable system. ✧ Software design ▪ Design a software structure that realises the specification; ✧ Implementation ▪ Translate this structure into an executable program; ✧ The activities of design and implementation are closely related and may be interleaved. Chapter 2 Software Processes 6 A general model of the design process Chapter 2 Software Processes 7  Design activities ✧ Architectural design, where you identify the overall structure of the system, the principal components (sometimes called sub-systems or modules), their relationships and how they are distributed. ✧ Interface design, where you define the interfaces between system components. ✧ Component design, where you take each system component and design how it will operate. ✧ Database design, where you design the system data structures and how these are to be represented in a database. Chapter 2 Software Processes 8  Software validation ✧ Verification and validation (V & V) is intended to show that a system conforms to its specification and meets the requirements of the system customer. ✧ Involves checking and review processes and system testing. ✧ System testing involves executing the system with test cases that are derived from the specification of the real data to be processed by the system. ✧ Testing is the most commonly used V & V activity. Chapter 2 Software Processes 9 Stages of testing Chapter 2 Software Processes 10 Testing stages ✧ Development or component testing ▪ Individual components are tested independently; ▪ Components may be functions or objects or coherent groupings of these entities. ✧ System testing ▪ Testing of the system as a whole. ✧ Acceptance testing ▪ Testing with customer data to check that the system meets the customer’s needs. Chapter 2 Software Processes 11 Testing phases in a plan-driven software process Chapter 2 Software Processes 12  Software evolution ✧ Software is inherently flexible and can change. ✧ As requirements change through changing business circumstances, the software that supports the business must also evolve and change. ✧ Although there has been a demarcation between development and evolution (maintenance) this is increasingly irrelevant as fewer and fewer systems are completely new. Chapter 2 Software Processes 13 System evolution Chapter 2 Software Processes 14