Coming up: Prescriptive Models 1

Software Engineering: A Practitioner’s Software Engineering: A Practitioner’s Approach, 7/eApproach, 7/e

Chapter 2Chapter 2Prescriptive Process ModelsPrescriptive Process Models

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Last time: Different families of Last time: Different families of modelsmodels

2

Prescriptive Agile

Goal: Higher Quality Software

Philosophy:•Bring order to chaos•Provide repeatability/consistency•Provide ability to control•Provide ability to coordinate teams

Goal: Higher Quality Software

Philosophy:•Individuals and interaction over process and tools•Working software over large documentation•Customer collaboration over contract negotiation•Responding to change over following a plan

Last time

We discussed how prescriptive models seems to have lost their popularity, while agile models have been gaining in popularity

What are some possible reasons for this?

Coming up: The Waterfall Model 4

Prescriptive ModelsPrescriptive Models

Prescriptive process models advocate an orderly approach Prescriptive process models advocate an orderly approach to software engineeringto software engineering

That leads to a few questions …That leads to a few questions … If prescriptive process models strive for structure and If prescriptive process models strive for structure and

order, order, are they inappropriate for a software world that are they inappropriate for a software world that thrives on change?thrives on change?

Yet, if we reject traditional process models (and the order Yet, if we reject traditional process models (and the order they imply) and replace them with something less they imply) and replace them with something less structured, structured, do we make it impossible to achieve do we make it impossible to achieve coordination and coherence in software work?coordination and coherence in software work?

Coming up: The V-Model 5

The Waterfall The Waterfall ModelModel

Communication Planning

ModelingConstruction

Deployment analysis design code

test

project initiation requirement gathering estimating

scheduling tracking

delivery support feedback

Use when:

-Requirements are stable and well-understood, very

short timeline (maintenance fixes)

Why was the waterfall model designed?

Invented in 1970 It is frequently true that time spent at the

beginning of the product lifecycle cuts down on the work in later stages How much time does maintenance consume?

The biggest lesson learned is that waterfall models Generally don’t work Because it’s unrealistic to not have change

The V-ModelThe V-Model

7

Same as Waterfall, diagram used to emphasize types of testing are linked to different phases in the model

-Requirements are stable and well-understood

Coming up: The Incremental Model

The V model

Focuses on verification and validation

Coming up: The Incremental Model 9

The Incremental The Incremental ModelModel

C o m m u n i c a t i o n

P l a n n i n g

M o d e l i n g

C o n s t r u c t i o n

D e p l o y m e n t

d e l i v e ry f e e d b a c k

analys is

des ign code

t es t

increment # 1

increment # 2

delivery of 1st increment

delivery of 2nd increment

delivery of nth increment

increment # n

project calendar time

C o m m u n i c a t i o nP l a n n i n g

M o d e l i n g

C o n s t r u c t i o n

De p l o y m e n t

d e l i v e r y

f e e d b a c k

analys is

des ign code

t es t

C o m m u n i c a t i o nP l a n n i n g

M o d e l i n g

C o n s t r u c t i o n

D e p l o y m e n t

d e l i v e r y

f e e d b a c k

analys is

des igncode t es t

Coming up: The RAD Model 10

The Incremental The Incremental ModelModel

Requires: Operational product that provides some value to users at each increment.

Advantages

-Helps users get software faster-Provides ability for the team to evaluate and replan-May complete an initial functionality to get buy- in or funding for later increments

Disadvantages

-May not be good for very risky systems-Full working systems may require long increments

Coming up: The RAD Model 11

The RAD ModelThe RAD Model

Communication

Planning

Modelingbusiness modeling data modeling process modeling

Constructioncomponent reuse automatic code generation testing

Deployment

60 - 90 days

Team # 1

Modelingbusiness modeling

data modeling process modeling

Constructioncomponent reuse automatic code

generation test ing

Modelingbusiness modeling data modeling process modeling

Const ruct ioncomponent reuse automatic code generation testing

Team # 2

Team # n

integration delivery feedback

Coming up: Evolutionary Models: Prototyping 12

The RAD ModelThe RAD Model

RAD = Rapid Application Development

Requires: very well understood requirements.

Very fast cycles (60-90 days) to create a lot of functionality

Emphasizes use of existing components/automatic code generation

Challenges:- Large staff needed to form RAD teams- Must have modularizable based software- Developers and Customers must be willing to make quick decisions- Time-consuming overall system tuning is difficult

Coming up: Evolutionary Models: The Spiral 13

Evolutionary Models: Evolutionary Models: PrototypingPrototyping

Communication

Quick plan

Construction of prototype

Modeling Quick design

Delivery & Feedback

Deployment

communication

Quickplan

ModelingQuick design

Constructionof prototype

Deploymentdelivery &feedback

Used when partial system can be delivered, then evolved into full system

Prototyping is a tool that can be used during any process

Used when customer only has a vague idea of what they want

Plan to either throw-away or evolve into real product -- there will be pressure at the end to evolve into the real product

Coming up: Still Other Process Models 14

Evolutionary Models: The Evolutionary Models: The SpiralSpiral

communication

planning

modeling

constructiondeployment delivery feedback

start

analysis design

code test

estimation scheduling risk analysis

Complete highest risk items first

Used to mitigate risk on risk-intensive projects

Every spiral revises cost/budget/schedule/etc…

Coming up: The Unified Process (UP) 15

Still Other Process Still Other Process ModelsModels

Component based developmentComponent based development—the process to —the process to apply when reuse is a development objectiveapply when reuse is a development objective

Formal methodsFormal methods—emphasizes the mathematical —emphasizes the mathematical specification of requirementsspecification of requirements

AOSDAOSD—provides a process and methodological —provides a process and methodological approach for defining, specifying, designing, and approach for defining, specifying, designing, and constructing constructing aspectsaspects

Unified ProcessUnified Process—a “use-case driven, architecture-—a “use-case driven, architecture-centric, iterative and incremental” software process centric, iterative and incremental” software process closely aligned with the Unified Modeling Language closely aligned with the Unified Modeling Language (UML)(UML)

Can you guess which company uses the spiral model?

The Unified Process

What is it? Phases: inception, elaboration, construction, transition The phases are divided up into time-boxes (iterations) Each of these iterations results in some deliverable

increment

Coming up: UP Work Products 20

UP PhasesUP Phases

Inception Elaboration Construction Transition Production

UP Phases

Workflows

Requirements

Analysis

Design

Implementation

Test

Iterations #1 #2 #n-1 #n

Support

Coming up: Pick a model 21

UP Work ProductsUP Work ProductsInception phase

Elaboration phase

Construction phase

Transition phase

Vision document Init ial use-case model Init ial project glossaryInit ial business case Init ial risk assessment. Project plan, phases and iterations. Business model, if necessary. One or more prototypes Incept io n

Use-case modelSupplementary requirements including non-functional Analysis model Software architecture Description. Executable architectural prototype. Preliminary design model Revised risk listProject plan including iteration plan adapted workflows milestones technical work products Preliminary user manual

Design modelSoftware components Integrated software increment Test plan and procedure Test cases Support documentation user manuals installat ion manuals description of current increment

Delivered software increment Beta test reports General user feedback

Pick a modelPick a model

Developing software to automatically drive Developing software to automatically drive racecars through a track without crashing. This racecars through a track without crashing. This has never been attempted before under software has never been attempted before under software control. The requirements are stable.control. The requirements are stable.

Waterfall, Incremental, Spiral, Waterfall, Incremental, Spiral,

RAD?RAD?

22Coming up: Pick a model

Pick a modelPick a model

Developing software to track the financial Developing software to track the financial bailout. The software requirements are very bailout. The software requirements are very clear. You need to create a system to perform 3 clear. You need to create a system to perform 3 distinct tasks:distinct tasks: Display where the money wentDisplay where the money went Display the amount of money left and how it’s allocatedDisplay the amount of money left and how it’s allocated Allow people to request funds from a particular subset Allow people to request funds from a particular subset

of the moneyof the money All functions will interface with each other and the All functions will interface with each other and the

same underlying database.same underlying database. Waterfall, Incremental, Spiral, RAD?Waterfall, Incremental, Spiral, RAD?

23Coming up: Pick a model

Pick a modelPick a model

25

Just checking if you were awakeJust checking if you were awake

Coming up: Prescriptive Software Models

26

Prescriptive Software ModelsPrescriptive Software Models

Variations of these models are VERY commonly used todayVariations of these models are VERY commonly used today If you think about it, they are focused in different areas, If you think about it, they are focused in different areas,

but have many similarities but have many similarities (all do the basic structure -- (all do the basic structure -- communication, planning, construction, testing, communication, planning, construction, testing, deployment, maintenance)deployment, maintenance)

You will almost definitely do some version of these You will almost definitely do some version of these processes when you graduateprocesses when you graduate

If you had never been to CS421, and never learned them, If you had never been to CS421, and never learned them, and then started your own company, you would STILL do and then started your own company, you would STILL do your own version of these processes… they make sense!your own version of these processes… they make sense!

End of presentation