Designed Stickiness - Speaker Deck

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Designed Stickiness @mathiasverraes

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@mathiasverraes verraes.net Student of Systems Meddler of Models Labourer of Legacy

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Let's talk about metaphors that stick

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Great metaphors create opportunity

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( ... even if it takes a while )

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«Breakthrough: An opportunity opens up to transform your software into something more expressive and versatile than you expected.»1 1 "Domain-Driven Design", Eric Evans, 2004

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Breakthroughs are often linguistic.

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Language is not a tool like metalworking or writing It's how our brains are wired2 2 "The Language Instinct - How the Mind Creates Language", Steven Pinker, 1994

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Some language is more sticky Advertisers learned this a long time ago

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Ceci n'est pas le Ping-Pong.

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Microservices vs SCS-architecture

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The optimistic age of OOP Objects as a thinking tool4 Anthropomorphic objects5 Objects as projections of the mind ... 5 "Object Design: Roles, Responsibilities, and Collaborations", Rebecca Wirfs-Brock & Alan McKean, 2003 4 "Object Thinking", David West, 2004

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Mainstream OOP: Objects as a way to structure imperative code

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Logger { log(...) { ... } }

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Execution in the Kingdom of Nouns6 6 http://steve-yegge.blogspot.be/2006/03/execution-in- kingdom-of-nouns.html

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A healthy obsession with language

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Log { append(...) { ... } }

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Metaphors as objects

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«His people are completely literal. Metaphors go over his head.»

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«Nothing goes over my head. My reﬂexes are too fast, I would catch it.»

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Example: Data Matching Paying money based on usage of content Determine ownership based on matches in data

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Data sources: Own research by employees Off shore data cleaning Public wiki-style Public but curated Private, paid Direct submissions from individuals Agencies representing owners

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Lots of incentives for fraud

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Is this our Core Domain? ✗ It's just technical data imports ⬜ ⬜ ⬜ ⬜

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Is this our Core Domain? ✗ It's just technical data imports ✗ Business is not interested ⬜ ⬜ ⬜

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Is this our Core Domain? ✗ It's just technical data imports ✗ Business is not interested ✔ Money changing hands ⬜ ⬜

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Is this our Core Domain? ✗ It's just technical data imports ✗ Business is not interested ✔ Money changing hands ✔ The code you keep secret ⬜

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Is this our Core Domain? ✗ It's just technical data imports ✗ Business is not interested ✔ Money changing hands ✔ The code you keep secret ✔ Oldest code in the system

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Event Storming

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Temporality The quality of data changes over time, based on who changes it

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Missing concept: Matching Data => ?

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Missing concept: Matching Data => Earning Trust

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Trust as a sticky metaphor Adopted by business

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Adopted into Ubiquitous Language

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The business started getting interested and involved

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What if Trust was a tangible thing in our domain model?

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Trust as a Value Object

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Trust can be passed around

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Trust attracts behaviour

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Strategies for changing Trust Event-based workﬂows

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0 <-> 5 <-> 10

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A Trust Arithmetic Invented by the business 0 <-> 5 <-> 10 Group (closure, associativity, identity, invertibility)

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«Habitable software (...) enables people to understand its construction and intentions and to change it comfortably and conﬁdently.»7 Programmers are not the only ones inhabiting our systems 7 "Patterns of Software", Richard P. Gabriel, 1996

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Example: Phone call bill rating

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Price per minute, price after the 60th minute Bundles: Credit minutes, lower rates Subscriptions: recurring bundles Promotions and incentives End of month transfers, expiries Flexible rating strategies in different markets

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"It's just an algorithm"

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Missing Metaphor: Buckets

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Mental Model ~ Visual Model ~ Implementation Model

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New opportunity: Long lead time to change pricing => Lively experimentation with pricing

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System Metaphors (XP) are too ambitious

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Metaphors are not speciﬁcations

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Small, local metaphors

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How to ﬁnd metaphors? It's not magic, it's awareness

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Modelling is spending time with the problem

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Obsess over language

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Visualise different models (structural, temporal, spatial...)

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Grasp the underlying principles of the problem and the domain

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«[A paradigm change] can happen in a millisecond. All it takes is a click in the mind, a falling of scales from the eyes, a new way of seeing.»8 8 "Thinking in Systems", Donella H. Meadows, 2008

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Thank you — verraes.net @mathiasverraes verraes.net/workshops dddeurope.com