A Prototyping Lifecycle
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Transcript A Prototyping Lifecycle
A Prototyping Lifecycle
The Waterefall Model and
Prototyping
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
A “prototyping” RAD lifecycle proposed instead
– rejected as “unmanageable”
– prototyping restricted to requirements gathering
RAD has re-emerged in the last two years
DSDM2- a RAD Process
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
“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
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
Aim is to gain understanding of the business
processes of the client organisation
The activity is strongly collaborative
– involves facilitated workshops
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
Other deliverables are System Architecture Definition and
Outline Prototyping Plan
DSDM Functional Model
Iteration
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
Delivers Analysis model(s) and major software
components
DSDM Functional Iteration
(contin.)
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
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
Covers cutover from development
environment to operational environment
Products include
–
–
–
–
delivered system and documentation
User Manual
trained user population
Project Review Document
Principles of DSDM
Active user involvement is imperative
DSDM teams must be empowered to make
decisions
Focus is on frequent delivery of products
Fitness for purpose is the essential criterion for
acceptance of deliverables
Iterative and incremental development is
necessary to converge on an accurate business
solution
All changes during development are reversible
Principles of DSDM (contin.)
Requirements are base-lined at a high level
Testing is integrated throughout the lifecycle
A collaborative and co-operative approach
between all stakeholders is essential