A Prototyping Lifecycle

The Waterefall Model and Prototyping 4 As early as the 1980’s the classic “Waterfall model” of software development was criticised –as a “fake” –as failing to address the fundamental issue of the software crisis incomplete, inaccurate, changed requirements –for pushing user evaluation to the end of the lifecycle 4 A “prototyping” RAD lifecycle proposed instead –rejected as “unmanageable” –prototyping restricted to requirements gathering 4 RAD has re-emerged in the last two years

DSDM2- a RAD Process 4 The Dynamic Systems Development Method (DSDM2) is a public domain standard specification for a Rapid Application Development (RAD) or evolutionary delivery process –supported by more than 200 companies in the UK –worthy as an example of a modern, industrial strength, lifecycle for prototyping

DSDM Overview 4 “Three pizzas and a cheese”: the five phases of DSDM are: 1. Feasibility study 2. Business study 3. Functional model iteration 4. System design and build iteration 5. Implementation

“Three Pizzas and a Cheese”

DSDM Feasibility Study 4 An assessment of whether or not DSDM is appropriate to the project. –Has serious impact on user community; worth it in trade-off to deliver in sharp time-scales? –Feasibility study should be short, sharp –Deliverables include Feasibility Report; Outline Development Plan and a fast prototype

DSDM Business Study 4 Aim is to gain understanding of the business processes of the client organisation 4 The activity is strongly collaborative –involves facilitated workshops 4 First deliverable is a Business Area Definition –high-level, prioritised, view of processes to be automated –identifies business processes, user classes, user representatives for development 4 Other deliverables are System Architecture Definition and Outline Prototyping Plan

DSDM Functional Model Iteration 4 Shares with the Design and Build Iteration the following cycles of four activities : 1. Identify what you are doing in the cycle 2. Agree how you will go about doing it 3. Do it 4. Check that you did it right by reviewing documents, demonstrating a prototype or software testing 4 Delivers Analysis model(s) and major software components

DSDM Functional Iteration (contin.) 4 Other products include –Prioritised functions core functions are guaranteed delivery –Functional prototyping review documents maintains history of user feedback –Non-functional requirements –Risk analysis of future development

DSDM Design and Build Iteration 4 Product is the Tested System –tests are iterative –tested system will not necessarily deliver ALL requirements, but will deliver the core “minimum usable subset”) –early deliverables are design prototypes and design prototyping review documents.

DSDM Implementation 4 Covers cutover from development environment to operational environment 4 Products include –delivered system and documentation –User Manual –trained user population –Project Review Document

Principles of DSDM 4 Active user involvement is imperative 4 DSDM teams must be empowered to make decisions 4 Focus is on frequent delivery of products 4 Fitness for purpose is the essential criterion for acceptance of deliverables 4 Iterative and incremental development is necessary to converge on an accurate business solution 4 All changes during development are reversible

Principles of DSDM (contin.) 4 Requirements are base-lined at a high level 4 Testing is integrated throughout the lifecycle 4 A collaborative and co-operative approach between all stakeholders is essential