1 SOFTWARE LIFE-CYCLES Elements and Definitions

2 Requirements System Design Detailed Design Implementation Installation & Testing Maintenance The WATERFALL LIFE-CYCLE

3 Life Cycle ANSI / IEEE Std A life-cycle is –a period of time that –starts when a software product is conceived and –ends when the product is no longer available for use. ==> Organised in phases

4 Phases of a Life-Cycle Requirements System Design Detailed Design Implementation Testing & Installation Operations & Maintenance Retirement

5 A phase is a –period of time within a life-cycle –that has a defined goal and –is based on result(s) of earlier phases.

6 Phases are activities – that transform inputs into outputs and – interact so that the transformation goes from abstract needs to correct source-code. ==> results (= inputs & outputs): documents ==> verify transformations at milestones

7 Documentation internal technical documentation external technical documentation end-user documentation for each version and release ==> supported by standards

8 internal technical documentation: –the results of each phase –the rationale and assumptions behind the decisions made in each phase –layouts and results of tests –error & fixes log

9 external technical documentation: –system structure –required environment –instructions for installation –maintenance & operation –guidelines for trouble shooting

10 end-user documentation: –user handbook –quick reference –guided tour –standard set-up

11 Milestone A scheduled event –for which some project member or manager is accountable and –that is used to measure progress.

12 ==> supported by standards A milestone includes typically - a formal review, - the issuance of documents and - the delivery of an (intermediate) product.

13 Standards Project independent –rules and procedures –embedded in a common system of terms –and quality criteria –that ensure inter-project adaptability –and compatibility of solutions. Important organisations: ANSI, IEEE

14 Requirements System Design Detailed Design Implementation Installation & Testing Maintenance The WATERFALL LIFE-CYCLE Standards Milestones Documents

15 End of Section 1b coming up: alternatives to the waterfall model