ch27 - Software change l Managing the processes of software...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 27 Slide 1 Software change l Managing the processes of software system change
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 27 Slide 2 Objectives l To explain different strategies for changing software systems Software maintenance Architectural evolution Software re-engineering l To explain the principles of software maintenance l To describe the transformation of legacy systems from centralised to distributed architectures
Background image of page 2
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 27 Slide 3 Topics covered l Program evolution dynamics l Software maintenance l Architectural evolution
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 27 Slide 4 Software change l Software change is inevitable New requirements emerge when the software is used The business environment changes Errors must be repaired New equipment must be accommodated The performance or reliability may have to be improved l A key problem for organisations is implementing and managing change to their legacy systems
Background image of page 4
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 27 Slide 5 Software change strategies l Software maintenance Changes are made in response to changed requirements but the fundamental software structure is stable l Architectural transformation The architecture of the system is modified generally from a centralised architecture to a distributed architecture l Software re-engineering No new functionality is added to the system but it is restructured and reorganised to facilitate future changes l These strategies may be applied separately or together
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 27 Slide 6 l Program evolution dynamics is the study of the processes of system change l After major empirical study, Lehman and Belady proposed that there were a number of ‘laws’ which applied to all systems as they evolved l There are sensible observations rather than laws. They are applicable to large systems developed by large organisations. Perhaps less applicable in other cases Program evolution dynamics
Background image of page 6
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 27 Slide 7 Lehman’s laws Law Description Continuing change A program that is used in a real-world environment necessarily must change or become progressively less useful in that environment. Increasing complexity As an evolving program changes, its structure tends to become more complex. Extra resources must be devoted to preserving and simplifying the structure. Large program evolution Program evolution is a self-regulating process. System attributes such as size, time between releases
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/09/2009 for the course SE 120336 taught by Professor Unknown during the Spring '09 term at Avila University.

Page1 / 39

ch27 - Software change l Managing the processes of software...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online