What we talk about when we talk about software Evolving thoughts about metaphor, software & influence Nat Pryce nat@natpryce.com @natpryce github.com/npryce speakerdeck.com/npryce

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

The desktop user interface

Block-based programming

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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

An experience with system metaphor

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

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…”

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

Figurative metaphor is technical debt

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

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…”

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

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

Figurative metaphor invokes conscious thought Cognitive metaphor shortcuts conscious thought

A layered architecture diagram Where would you draw the user interface? Hardware Device Drivers Operating System Application

Did I predict your answer? Hardware Device Drivers Operating System Application User Interface

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

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

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

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

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

Example Introducing agile development to upper management

How we describe a system influences how we plan to build it A linear metaphor led to ● A development plan that implemented each business process stage in turn ● An planned big-bang release of all functionality ● Missed deadlines and eventual cancellation of the project Publication Payment Licensing Decision Review Reviewer invitation Quality check Manuscript Submission

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.”

Reformulated as containment and facing

Example Informing the reorganisation of product development teams

Metaphors: size/strength, proximity Initially we drew components close to the users they serve. Then drew line thickness to show where changes will probably have to be made in both communicating services. Metaphorically: how strongly components are "pulled towards one another"

Informing team (re)organisation Development teams (Green) should look after components that change at the same time. Product managers (Pink) should work across teams, and focus on the user journeys for specific segments of our user base.

Summary ❖ Metaphor maps behaviour from one domain to another ❖ Metaphor can help but also hinder ❖ Figurative metaphor is technical debt ❖ Cognitive metaphor is inescapable ❖ Cognitive metaphor is understood unconsciously

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