What we talk about when we talk about software

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What we talk about when we talk about software Evolving thoughts about metaphor, technical debt & Conway's law Nat Pryce nat@natpryce.com @natpryce github.com/npryce speakerdeck.com/npryce

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A layered architecture diagram Hardware Device Drivers Operating System Application Hardware Device Drivers Operating System Application Or? Which feels right?

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The desktop user interface

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Metaphor stretched ad absurdum

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Block-based programming Image CC-BY-SA 2.0 Wikipedia user Infofiltrage

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Unix pipes tr -cs A-Za-z '\n' | tr A-Z a-z | sort | uniq -c | sort -rn | sed ${1}q

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“Each XP software project is guided by a single overarching metaphor. Sometimes the metaphor is "naive". ... Sometimes the metaphor needs a little explanation. The words used to identify technical entities should be consistently taken from the chosen metaphor.” eXtreme Programming Explained, Kent Beck, 1999 XP's system metaphor

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An experience with system metaphor

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In software, metaphor maps not just names but affordances from the familiar to the unfamiliar

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Figurative metaphor Metaphors We Live By, Lakoff and Johnson, 1980. “...in getting us to try to understand how it could be true, it makes possible a new understanding…”

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Figurative metaphor has a sell-by date iOS 6 iOS 7

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Idioms: metaphors that have kicked the bucket Figurative metaphors can become common phrases in language When we forget the original meaning of the phrase, it loses its explanatory power. The phrase fossilises as an idiom

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Technical idioms Library Patch Log

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Figurative metaphor is technical debt

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Cognitive metaphor We live ➢ in the physical world ➢ in social groups We conceptualise anything more abstract as metaphor

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Example: MORE IS UP From The Guardian website, 15/05/2014: “OVO Energy raises prices 3%” “...soaring values have revived idea of selling part of property portfolio...” “...nation's top 10% owning 44% of household wealth...” “Ministry of justice figures show number of convictions fell by only 69...” “Labour's nosedive in the opinion polls…”

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Cognitive metaphor domains Up/Down, Close/Far, Facing towards/away Large/Small Inside/Outside, Boundary, Surface Extent, Covering, … Light/Heavy Bright/Dark Parent/Child, Siblings, ... ... Orientation Size Containment Surface Weight Shade Family ...

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A layered architecture diagram Hardware Device Drivers Operating System Application Hardware Device Drivers Operating System Application Or? Which feels right?

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Where do you draw the user interface? Hardware Device Drivers Operating System Application User Interface

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Mapping onto different target domains Up Down etc. More Less Happy Sad Pure Corrupt Abstract Concrete People Animals Controlling Controlled

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Vertical orientation in UML Or? Shape Circle Rectangle Shape Circle Rectangle Which feels right?

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Vertical orientation ABSTRACT IS UP CONTROL IS UP PEOPLE IS UP HARDWARE IS DOWN (STATIC) DEPENDENCIES POINT DOWNWARDS ...

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Containment PROGRAMMING LANGUAGES ARE CONTAINERS CONTROL AT THE CENTER VULNERABLE IN THE CENTER “The code is written in Java” Encapsulation Leaky abstractions CPU & peripherals ...

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User-facing features Front-end developer Database back-end Externally facing services ... Orientation: facing towards something THE SYSTEM FACES THE USER THE SYSTEM FACES OTHER SYSTEMS

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Size Big Data “Big Iron” (mainframes) Software design diagrams could make better use of BIG IS IMPORTANT BIG IS IMPORTANT BIG IS POWERFUL

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Example: size related to importance https://en.wikipedia.org/wiki/Sociogram

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Entailment and coherence Read: “Following the report, shares in XYZ Plc took a nosedive and were in freefall by close of trading.” Think: “I should bail out of my investment in XYZ Plc. before the stock hits rock bottom.”

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Database ORM Domain Model UI Or? Database ORM Domain Model UI Which feels right? Inadvertent entailment: layers, balance, size

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Metaphorical blinkers Image CC-BY-SA 2.0 Pete Markham Metaphors We Live By, Lakoff and Johnson, 1980. “In allowing us to focus on one aspect of a concept, a metaphorical concept can keep us from focusing on other aspects of the concept that are inconsistent with the metaphor.”

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How we describe a system affects how we plan to build it Linear metaphor led to linear development and a big-bang release of all functionality Publication Payment Licensing Decision Review Reviewer invitation Quality check Manuscript Submission

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An alternative depiction Reformulate the solution in terms of containment & facing

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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. – Melvin Conway

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Conway's Law rephrased If you have four groups working on a compiler, you'll get a four-pass compiler. – Eric S. Raymond

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Conway's Law rephrased If you have four groups working on a compiler, you'll get a four-pass compiler. – Eric S. Raymond

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Conway's Law rephrased If you have four groups working on a compiler, you'll get a four-pass compiler. – Eric S. Raymond

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Conway's Law rephrased If you have four groups working on a compiler, you'll get a four-pass compiler. – Eric S. Raymond A metaphor

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Metaphor precedes Conway's Law

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Summary ❖ Metaphor maps behaviour from one domain to another ❖ Metaphor helps and hinders ❖ Figurative metaphor is technical debt ❖ Cognitive metaphor is inescapable ❖ Metaphor precedes Conway's Law