the architect's clue bucket

The architect's clue bucket

Ruth Malan

Image source: wikipedia

#OReillySACon

We are what we think.All that we are arises with our thoughts.With our thoughts we make the world.

– The Dhammapada

@RuthMalan#OReillySACon

I think about architecture

and what architects do

The architect has structural oversight

And makes tradeoffs

because… there’s only so much rope

and why

conveys behavior

Structure

to delight users

at scale

across contexts

and more why

when there’s tight coupling and bad code smells…

… the architect must address The Kludge

and why (again)Because mounting technical debt, ties the system to the past

… by its shoelaces

and howDraw on the walls!

and more howiterate

and experiment

to achieve fit to context and to purpose

Actually, a lot about how

I’m not kidding!DELIBERATEREASONDISCUSSDECIDERECONSIDER

DELIBERATION, n. The act of examining one's bread to determine which side it is buttered on.

REASON, v.t. To weight probabilities in the scales of desire.DISCUSSION, n. A method of confirming others in their errors.DECIDE, v.i. To succumb to the preponderance of one set of

influences over another set.RECONSIDER, v. To seek a justification for a decision already made.

— Ambrose Bierce, The Devil's Dictionary

Well, now I am

But not about drawing on the walls!


Where We’re Headed:• some clues: design

principles, heuristics, tips, … and hints

• organizing clues: mapping the clue landscape

• getting clues: where and how to look


“Architects must haveself-repairing egos”— Dana Bredemeyer


The architect’s SCARS:• Separation of Concerns• crisp and resilient

Abstractions• balanced distribution of

Responsibilities• strive to Simplify — Grady Booch


Separation of Concerns

“I go along with the natural makeup”…“when I come to the tricky parts, I slow down” — Chuang Tzu:

“The Dexterous Butcher”

Layers

presentation

business logic

data access

1996

SCARS: Separation of Concerns

application

domain

Source: geekandpoke.typepad.com/geekandpoke/2011/03/architectural-best-practices.html

(in 2011)

Layers

presentation

business logic

data access

1996


application

domain

— Ambrose Bierce, Devil’s Dictionary

ABATIS, n. [1.] Rubbish in front of a fort, to prevent the rubbish outside from molesting the rubbish inside.

Image: Engineering and the Mind’s Eye

— Ambrose Bierce, Devil’s Dictionary

ABATIS, n. [1.] Rubbish in front of a fort, to prevent the rubbish outside from molesting the rubbish inside.

Image: Engineering and the Mind’s Eye

“Design things to make their performance as insensitive to the unknown or uncontrollable external influence as practical.” — Eb Rechtin

Image: alistair.cockburn.us/Hexagonal+architecture


Hexagonal Architecture

Ports and adapters

Microservices!(in 2016)

Image: martinfowler.com/articles/microservices.html

Image: martinfowler.com/bliki/BoundedContext.html

Bounded Contexts in DDD


“There was a wall. It did not look important. It was built of uncut rocks roughly mortared. An adult could look right over it, and even a child could climb it. Where it crossed the roadway, instead of having a gate it degenerated into mere geometry, a line, an idea of boundary. But the idea was real. It was important. For seven generations there had been nothing in the world more important than that wall.Like all walls it was ambiguous, two-faced. What was inside it and what was outside it depended upon which side of it you were on.”

— Ursula K. Le Guin, The Dispossessed

Image: welshwaller.files.wordpress.com/2013/01/llwest-and-elan-valley-017.jpg

Boundaries: Conway’s Law

“Any organization that designs a system (defined broadly) will

produce a design whose structure is a copy of the organization's communication structure.”

—Melvyn Conway (in 1968!)


As programmers we deal with abstractions all the time and

we have to invent them in order to solve our problems

— Michael Feathers

SCARS: crisp and resilient Abstractions


“The purpose of abstraction is not to be vague, but to create a new semantic level in which one can be absolutely

precise.” — Dijkstra


Crisp Abstractions

Single Responsibility at the level of abstraction of the abstraction


Crisp and Resilient Abstractions

“We propose instead that one begins with a list of difficult design decisions or design

decisions which are likely to change. Each module is then designed to hide such a

decision from the others.” — David Parnas


Resilient AbstractionsResilient under change

SRP: each software module should have one and only one reason to change (Uncle Bob Martin)

Retrospective (Feathers)Prospective (thought experiments)



SCARS: balanced distribution of Responsibilities

No “god” component(s)


SCARS: strive to Simplify

“Simplify, simplify” — H. D. Thoreau

‘One “simplify” would have sufficed’ — Ralph Waldo Emerson, in response

“Simplify, simplify, Simplify”

“Communicate, Communicate, Communicate”

— Eberhardt Rechtin


“Do the simplest thing that could possibly work”

Occam’s Razor: the simplest solution is usually the correct one

YAGNI


Chad Fowler: “The older I get, the more I realize the biggest problem to solve in tech is to get people to stop making things harder than they have to be.”

Michael Feathers: “It's not that easy.”


focusing is saying “no”— Steve JobsGoogleX


“old code doesn’t die; you have to kill it”

— Grady Booch


How to kill codeStranglerApplication: “An alternative route is to gradually create a new system around the edges of the old, letting it grow slowly over several years until the old system is strangled.”

— Martin Fowler


“disorder is easier and more permanent than order, which is difficult and

temporary”

— Jeremy Campbell


“One bad programmer can easily create two new jobs a year.”

— David Parnas



The architect’s SCARS:• Separation of Concerns• crisp and resilient

Abstractions• balanced distribution of

Responsibilities• strive to Simplify — Grady Booch


Essence of systems is:• Relationships• Interfaces• Form• Fit• Function



Essence of systems is:• Relationships• Interfaces• Form• Fit• Function


“Relationships among the elements are what give systems their added value”

“Don’t partition by slicing through regions where high rates of information exchange are required””


Essence of architecture is:• Structuring• Simplification• Compromise• Balance


“dependencies are a tradeoff between the cost of maintaining the code yourself (and implementing it) & the cost of the risk of breakage” — Kent Beck

Balance: Tradeoffs/Compromise

Kent Beck’s 4 Rules of Simple Design

• passes its tests• minimises

duplication• reveals its intent• has fewer

classes/modules/packages…

More Clues

Systemantics by John Gall• New systems mean new problems• A complex system that works is invariably

found to have evolved from a simple system that worked• a complex system designed from scratch

never works and cannot be made to work• Systems develop goals the minute they come

into being

“Uncle Bob” Martin’s SOLID• Single Responsibility Principle

(SRP)• Open/Closed Principle (OCP)• Liskov Substitution Principle

(LSP)• Interface Segregation

Principle (ISP)• Dependency Inversion

Principle (DIP)

More Clues

97 Things

101 Things“Architecture is the thoughtful making of space."-LOUIS KAHN”

“Science works with chunks and bits and pieces of things with the continuity presumed, and [the artist] works only with the continuities of things with the chunks and bits and pieces presumed."-ROBERT PIRSIG, ZEN AND THE ART OF MOTORCYCLE MAINTENANCE”

“Just because an interesting idea occurs to you doesn't mean it belongs in the building you are designing. Subject every idea, brainstorm, random musing, and helpful suggestion to careful, critical consideration.” ― Matthew Frederick

https://www.goodreads.com/author/show/889660.Matthew_Frederick

“If you’re waiting on me to come to a conclusion where I give you a score from one through ten on the NDUF to BDUF scale (and it’s obviously five, right?), you’re going to be disappointed with this post. How much design should you do up front? Dude, I have no idea. Are you building a lunar rover? Probably a lot, then, because the Sea of Tranquility is a pretty unresponsive product owner. Are you cobbling together a minimum viable product and your hardware and business requirements may pivot at any moment? Well, probably not much. I can’t settle your design decisions and timing for you with acronyms or aphorisms.”

Erik Dietrich, Designs Don’t Emergehttp://www.daedtech.com/designs-dont-emerge/

http://www.daedtech.com/designs-dont-emerge/

Is this the part where we get to talk about Technical Wisdom?!

Wisdom factorsAnd factors and refactors


Next:• some clues: design




Maps: location, location, location

Maps asplaces to put things

Context System-in-Context(use, dev, ops)

System(Ecosystem)

Architecturestructure and mechanisms

“Requirements”design of system

capabilities

Strategyecosystem interventions

"Always design a thing by considering it in its next larger context" -- Eliel Saarinen

What

ARCHITECTURE

STRUCTURESoftware architecture refers to the high level structures of a software system, [..] It is the set of structures needed to reason about the software system. Each structure comprises software elements, relations among them, and properties of both elements and relations.

— wikipedia/Clements et al

“Good design doesn’t ’emerge’ like a welcome ray of sunshine

on a cloudy day.

—Erik Dietrich

Erik Dietrich, Designs Don’t Emergehttp://www.daedtech.com/designs-dont-emerge/

“It comes coughing, sputtering, screaming and grunting from the mud, like a drowning man being pulled from quicksand, and the effort of dragging it laboriously out leaves you

exhausted.”

Erik Dietrich, Designs Don’t Emergehttp://www.daedtech.com/designs-dont-emerge/Art by Amanda Muledy (@EEKitsabug)

Posit structure

Explore behavior

Revise structure

Explore — with sketches

Factor and Refactor

Posit responsibilities

Refine as explore behavior and different views

PatternsMetaphorsExperienceExisting stuff

“The responsibility of architecture is the architecture of responsibility.” -- Jan van Til

What

ARCHITECTURE

STRUCTURE

interfaces

elements and relationships

How

BEHAVIOR

What

ARCHITECTURE

STRUCTURE

Logical

Conceptual

Execution

What(system view)

HowWhat(user view)

SYSTEM ARCHITECTURE

STRUCTURALBEHAVIORALCAPABILITIESCONTEXT

Why

v v

How well

FUNCTIONAL PROPERTIES

What(system view)

HowWhat(user view)

SYSTEM ARCHITECTURE


Why

v v

How well


architecturally significant mechanisms

Architecturally Significant?

Architecturally significant?The demands (forces, properties, …) on the system that are challenging,

push the limits, require design attention

Source: Martin Fowlerhttp://martinfowler.com/articles/lmax.html

LMAX Disruptor MechanismChallenges: A trading platform needs very low latency - trades have to be processed quickly because the market is moving rapidly. A retail platform adds complexity because it has to do this for lots of people.

Context System-in-Context(use, dev, ops)

System(Ecosystem)

Architecturestructure and mechanisms

“Requirements”design of system

capabilities

Strategyecosystem interventions


the elephant in the room

Messy!right system built right

Messier!System Design Intent

(what should be)System Design Reflection

(what is)

Ask “What does the code need?”

“What does the system need?”“What does the ecosystem need?”

What(system view)

HowWhat(user view)

SYSTEM ARCHITECTURE


Why

v v

How well


good?right?successful?

What does it take to be successful?

Tell you a story… it was Alan Kay’s idea!

“the Constitution itself is a set of principles for building a very complex dynamic structure that should last for centuries”– Alan Kay

The Virginia

Plan

Image: ourdocuments.gov

The Constitutionof the

United States

“I confess that there are several parts of this constitution which I do not at present approve, but I am not sure I shall never approve them: For having lived long, I have experienced many instances of being obliged by better information, or fuller consideration, to change opinions even on important subjects, which I once thought right, but found to be otherwise. It is therefore that the older I grow, the more apt I am to doubt my own judgment, and to pay more respect to the judgment of others.”

— Benjamin Franklin

“The Federalist Papers are arguments that support different parts of the design of the Constitution. And the Constitution itself is a set of principles for building a very complex dynamic structure that should last for centuries”– Alan Kay

“it seems to have been reserved to the people of this country, [..], to decide the important question, whether societies of men are really capable or not, of establishing good government from reflection and choice, or whether they are forever destined to depend, for their political constitutions, on accident and force.”

Federalist No.1

The Federalist Papers, No. 51 addresses • checks and balances • separation of powers

Areas like• creativity and imagination• empathy, listening and observation• problem framing and solving

• perception and bias• experimentation

Personal Effectiveness

Areas like• Leadership• Collaboration• Communication and influence

• getting things done in organizations• Coach/consultant

Organizational Effectiveness“All problems are people

problems” — Jerry Weinberg

Areas like• Situational awareness

• context mapping• Differentiation and value definition• Direction setting

Strategic Effectiveness


Next:• some clues: design




Getting Clues: Steal

“Experience keeps a dear school, but fools will learn in no other.”

Benjamin Franklin

Steal: Stand on Shoulders

Shoulders to Stand On



Standing on Shoulders: by Analogy


Shoulders of Giants


More Getting Clues• Look• Listen• Ask• Imagine• Play

• Draw• Try• Try again• Show• Show again

Getting Clues: LookLarge portion of our brain is devoted to visual processing

Sighted people see all our waking hours

So we see, right?!

Getting Clues: Look“In fact, in medical terms, that’s our view.”

— Dan Ariely [joking]

“Are we in control of our own decisions?” Dan Ariely

Perception

Getting Clues: Lookhttps://www.xkcd.com/32/

Ladder of Inference

— Argyris and subsequently Peter Senge in Fifth Discipline

Getting Clues: Look

Pyramid of Belief

Getting Clues: LookLiminal thinking The pyramid of belief — Dave Gray

and self-sealing logic

Selection

Getting Clues: Look

What we are paying attention to, shapes what we perceive and pay

attention to.

Observe: Boyd’s OODA

Getting Clues: Look/Observe

Observe Orient Decide Act


“All architecture is design but not all design is architecture.Architecture represents the significant design decisions that shape a system, where significant is measured by cost of change.”

— Grady Booch, blog post, March 2, 2006


Getting Clues: Look/Observe

Title: short noun phraseContext: describes the forces at play; probably in tension, and should be called out as such Decision: describes our response to these forcesStatus: proposed, accepted, deprecated or supersededConsequences: describes the resulting context, after applying the decision

— Michael Nygard, Documenting Architecture Decisions, Nov 2011

Getting Clues: Look/Change PoV

“A change of perspective is worth

80 IQ points” — Alan Kay


Move to different PoV/vantage point• view system through different “lenses” — models (incl. instrumented

code), perspectives

Also, a matter of discipline• self-discipline, and • discipline of engineering: probe, model, reason, open criticism, come

up with counter arguments, come up with alternatives


“You don't understand something until you understand it more

than one way” — Marvin Minsky

Image: en.wikipedia.org/wiki/Marvin_Minsky#/media/File:Marvin_Minsky_at_OLPCb.jpg

“If you haven’t thought of three possibilities, you haven’t thought enough.” — Jerry Weinberg

Rule of Three


More Getting Clues• Listen• Ask• Empathize• Imagine• Play

• Draw• Map• Try • Try again• Show

Context Mapping

Getting Clues: MapImage: blog.gardeviance.org/2015/02/an-introduction-to-wardley-value-chain.html

Wardley (Value Chain) MapsGrove-styled Context Maps

Image: bluesummitstrategy.com

Getting Clues: Map

Maps of Code

Getting Clues: Map

(Hand-drawn) Maps of Code

Questions

Getting Clues: Ask

• why?• 5 why’s• what if? why not?• Kipling’s 6 honest serving men


More Getting Clues• Listen• Ask• Empathize• Imagine• Play

• Draw• Map• Try • Try again• Show


Still Getting Clues

Ruth Malan

Web: bredemeyer.comalso: ruthmalan.comTwitter: @ruthmalan