Evolutionary Design: Inductive and Deductive (Paris, oct 2017)

blog.adrianbolboaca.ro mozaicworks.com

Evolutionary Design:

Inductive and Deductive

Adrian Bolboacă@adibolb

[email protected]

http://blog.adrianbolboaca.ro/

http://mozaicworks.com/


Agenda

1.Objectives

2.Evolutionary Design

3.Inductive Evolutionary Design + coding

4.Deductive Evolutionary Design + coding

5.Deductive vs Inductive + discussion

6.Evolutionary Design Ideas

7.Conclusions & Retrospective




Objectives◊ Understand two opposite ways of designing

your software

◊ Learn when more suitable to be deductive and when inductive

◊ Patterns and anti-patterns of Evolutionary Design




Help me out

1.Do you practice TDD?

2.(if yes) How long have you used TDD?




Evolutionary Design

The art of growing a system by observing its natural traits and then normalizing and optimizing its growth




Evolutionary Design

Evolutionary design is about the transformations that take place when we add new behaviors / tests.




Inductive

Inductive reasoning makes broad generalizations from specific observations. Basically, there is data, then conclusions are drawn from the data. This is called inductive logic, according to Utah State University.



http://ocw.usu.edu/English/introduction-to-writing-academic-prose/inductive-and-deductive-reasoning.html


Inductive Evolutionary Design◊ Focus more on state behavior and less on

collaboration (interaction) behavior

ҩ Start with primitives

ҩ Test the logic of changing state

◊ Collaboration behavior is interesting just at the limit of the system




Inductive Evolutionary Design

1.Start from small details

a.Choose an entry point

b.Use Behavior Slicing to analyze the behaviors

c.Order the behaviors from simple to complex

2.Generalize the duplicated behaviors

a.Minimize non-accidental duplication in the code

b.Maximize the clarity of the concepts





3. Evolve small behaviors into design concepts

a.Move similar behavior in the same place

b.Maximize clarity of the moved behaviors

2.Generalize the design concepts

a.Use composition (or rarely inheritance)

b.Use Dependency Inversion to have a logical dependency graph

3.Evolve the design concepts into components

a.Modules

b.Bounded contexts




Inductive Design Characteristics◊ Behavior is important, not implementation

◊ Representation doesn’t matter in the beginning

◊ Tests are generalized while duplication is minimized

◊ Tests start by using primitives and end by using design concepts

◊ The representation can be changed and the tests should pass





A short coding demo




Inductive Design Layers

We start with primitives and we evolve the design in successive layers:

ҩ Scalar Primitive type (string, int, array, etc)→

ҩ Primitive type Field OR Parameter→

ҩ Field Settings Class→

ҩ Parameter Data Structure→

ҩ Logic Pure function→

ҩ Pure function Class function→

ҩ Class Component→




Inductive Evolutionary Design◊ Applies to:

ҩ Classicist state-based testing (Chicago School)

ҩ Bottom-up

ҩ Detailed micro-design (TDD As if you Meant It)




Deductive

Deduction, starts out with a general statement, or hypothesis, and examines the possibilities to reach a specific, logical conclusion, according to the University of California



http://www.csun.edu/science/ref/reasoning/deductive_reasoning/index.html


Deductive Evolutionary Design◊ Focus more on collaboration (interaction)

behavior

◊ Create a scaffolding

ҩ Guiding Test

ҩ Bounded Context with business entities

ҩ Walking Skeleton

◊ Deduce the design concepts depending on the scaffolding




Deductive Evolutionary Design

1.Start from the scaffolding

a.Identify the entry point

b.Find the next layer of collaboration (interaction)

c.Check the collaboration behavior between the entry point and the next layer

2.Move deeper to the next layer of collaboration (interaction)

a.Find the next layer of collaboration (interaction)

b.Check the collaboration behavior between the entry point and the next layer





3.Iteratively understand if you reached the end

a.Use guiding test

b.Have an acceptance test

2.Refactor the design concepts

a.Not having single responsibility

b.Being scattered across the system

c.That are unclear (purpose, naming, etc)




Deductive Design Characteristics◊ Behavior is important, not implementation

◊ Representation needs to be addressed minimally

◊ Tests are generic from the beginning

◊ Tests start by using design concepts

◊ The representation can be changed and the tests should pass

◊ The links between the design concepts is essential and made through their APIs and collaborators

◊ If collaboration behavior changes, the tests make refactoring difficult





A short coding demo




Deductive Evolutionary Design◊ Applies to:

ҩ Outside-in (London School)

ҩ Middle-top

ҩ Middle-bottom

ҩ Domain Driven Design (DDD)

ҩ Acceptance Test Driven Development (ATDD)




Deductive vs Inductive◊ When to use each?

◊ Can they be used in the same time?

◊ Are specific cases when one is more useful than the other?

◊




Evolutionary Design Ideas◊ The tests are pressure applied to existing design

◊ The production code is like clay that gets molded depending on the pressure applied to it

◊ When evolving the design of a system we observe growth patterns that simplify the resulting system

◊ Evolutionary Design is like helping your plants grow, knowing what measures to take so they will be fruitful




Anti-Patterns◊ Focus on implementation details and not on

design concepts

◊ Consider that tests are the essential output of TDD, and not well structured design elements

◊ Consider you know exactly the resulting design, and don’t listen to the design smells

◊ Focus on the solution and not on the problem




What’s Next?◊ Experiment both Deductive and Inductive

approaches during katas or coderetreats

◊ Try both Deductive and Inductive approaches in your production environment

◊ Watch my codecasts on TDD as if you Meant It & more blog.adrianbolboaca.ro/evolutionary-design

◊ Pair with many people and learn from them



http://blog.adrianbolboaca.ro/evolutionary-design


#RemotePairProgramming

Join my #RemotePairProgramming Codecasts: contact me and pair during a recorded codecast with me




Thank you!



Software

Evolutionary Design: Inductive and Deductive (Paris, oct 2017)