MDD

Wednesday, 21 September 2011

Systems Development Life Cycle Notes

Life Cycle Archetypes
A simple definition of the classical Systems Development Life Cycle (SDLC) depicts high tech systems development in terms of 4 main activities or phases (Racoon, 1995). Racoon’s insight was to interpret other life cycle models in terms of the SDLC. Racoon’s four life cycle archetypes are easily extended as variations on the theme of the SDLC as activities rather than as a sequence. If interpreted as a strict linear sequence the SDLC equates to the waterfall, if as overlapping phases it approximates the ‘V-model’, the spiral life cycle as lingering, and chaotic as all-at-once or code-and-fix. As Racoon suggests, life cycles are just our own perspectives “on the state of a project rather than any essential truth about the state of the project” (Racoon, 1995)
1) Requirements Analysis
2) Design
3) Implementation
4) Maintenance.
The waterfall model can be presented graphically in terms of SDLC activities as shown (below). The effort associated with these activities (or phases) can be plotted over time to create a shorthand representation of any life cycle in terms of the effort spent on these activities over time.

lifecycle_waterfall

lifecycle_sashimi

lifecycle_regression

lifecycle_chaos

Watefall

Sashimi

Regression

Chaotic

A life cycle can in principle be presented in similar fashion, for example the Rational Unified Process depicted below conforms roughly to Racoon's ‘Regression’ archetype.
ruphumpback

References:
Racoon, L. B. S. (1995) The chaos model and the chaos cycle. ACM SIGSOFT Software Engineering Notes, 20, 12.