Metaphors We Code By (Software Architect 2015)

Of the 12 XP practices that Kent Beck described in the “white book”, System Metaphor has seen little adoption while the others have been enthusiastically embraced and extended. In this presentation I explored why this might be so, and related XP’s notion of metaphor to conceptual metaphors that has been investigated by George Lakoff et al.

Lakoff’s research indicates that metaphors are inescapable when thinking and communicating about software. However, careless use of metaphor can hinder the process of designing software and communicating about software design. If we cannot avoid metaphor we must use it to our advantage and avoid its pitfalls.

Presented at Software Architect 2015, London, UK.

Transcript

1. Metaphors We Code By or What we talk about when we talk about software Nat Pryce nat@natpryce.com @natpryce github.com/npryce
2. Whatever happened to XP’s System Metaphor?
3. “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. As development proceeds and the metaphor matures, the whole team will find new inspiration from examining the metaphor.” eXtreme Programming Explained, Kent Beck, 1999 The White Book
4. [System Metaphor is] “What XP uses to unify an architecture and provide naming conventions. A simple shared story of how the system works, a metaphor. This story typically involves a handful of classes and patterns that shape the core flow of the system being built.” http://c2.com/cgi/wiki?SystemMetaphor as of 25/04/2014 The C2 Wiki
5. “System Metaphor is itself a metaphor for a simple design with certain qualities. The most important quality is being able to explain the system design to new people without resorting to dumping huge documents on them. A design should have a structure that helps new people begin contributing quickly. The second quality is a design that makes naming classes and methods consistent.” http://www.extremeprogramming.org/rules/metaphor.html as of 25/04/2014 Ron Jeffries’ Current Description of XP
6. An Experience with System Metaphor
8. The Embodied Mind We live ➢ in the physical world ➢ in a culture
10. 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…”
11. A Layered Architecture Diagram Hardware Device Drivers Operating System Application Hardware Device Drivers Operating System Application Or? Which feels right?
12. Mapping onto Different Target Domains Up Down etc. More Less Happy Sad Pure Corrupt Abstract Concrete People Animals Controlling Controlled
13. Vertical Orientation in UML Or? Shape Circle Rectangle Shape Circle Rectangle Which feels right?
14. Vertical Orientation ABSTRACT IS UP CONTROL IS UP PEOPLE IS UP HARDWARE IS DOWN (STATIC) DEPENDENCIES POINT DOWNWARDS ...
15. Types of Conceptual Metaphor One thing for another, physical for abstract Up/Down, Near/Far, Facing towards/away Large/Small Inside/Outside, Boundary, Surface Extent, Covering, … Light/Heavy Bright/Dark ... Ontological Orientation Size Containment Surface Weight Shade ...
16. Containment PROGRAMMING LANGUAGES ARE CONTAINERS CONTROL AT THE CENTER VULNERABLE IN THE CENTER “The system is in Java” Encapsulation Hexagonal Architecture Privilege ring levels ...
17. 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
18. Size Big Data “Big Iron” (mainframes) Software design diagrams could make better use of BIG IS IMPORTANT BIG IS IMPORTANT BIG IS POWERFUL
19. Example: Size Related to Importance https://en.wikipedia.org/wiki/Sociogram
20. 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.”
21. Inadvertent Entailment
22. Database ORM Domain Model UI Or? Which feels right? Database ORM Domain Model UI Inadvertent Entailment: Layers, Balance, Size
23. E.g. Tiers vs Layers Similar in real life Different technically Often conflated Image CC-BY-NC-ND 2.0 THEMACGIRL* Inadvertent Mixed Metaphors
24. Another Example: ARGUMENT IS WAR From The Guardian website, 17/05/2014: “Sussex police under fire for 'criminalising' fracking protests” “Nigel Farage has attempted to defend his controversial remarks...” “Michael Gove ordered to seal truce as Clegg hits back...”
25. Example: AN ARGUMENT IS A BUILDING “Alice's argument is supported by recent research.” “The foundations of Bob’s argument are rather shaky.” “Carol has put together a convincing case.”
26. ARGUMENT IS WAR AN ARGUMENT IS A BUILDING “To demolish my opponent’s argument I should undermine it by attacking its weak foundations.” Coherence Of Argument Metaphors
27. 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.”
28. Tip: Sketch a design in different ways
29. Conceptual / Conventional Metaphor Source Domain Target Domain
30. Figurative / Unconventional Metaphor Conventional Source Domain Target Domain Unconventional Source Domain
31. Figurative / Unconventional 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…”
32. The Desktop User Interface Metaphor Apple Lisa
33. Metaphor Stretched Ad Absurdum Microsoft Bob
34. Figurative Metaphor Has A Sell By Date iOS 6 iOS 7
35. Figurative Metaphor for Novice Programmers Scratch Image CC-BY-SA 2.0 Wikipedia user Infofiltrage
36. Figurative Metaphor to Explain Design A monad is...
37. Figurative Metaphor to Explain Design Logan Campbell
38. The map is not the territory
39. Tip: Watch your language! Design collaboratively Listen for metaphor Tacit assumptions? Tacit entailment?
40. 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
41. Technical Idioms Library Patch Log
42. Whatever happened to XP’s System Metaphor?
43. Summary ❖ Metaphor is inescapable ❖ Metaphor can help and hinder ❖ Be mindful of how we use metaphor
44. More Information Bibliography https://www.mendeley.com/groups/7679081/sw-metaphor/papers/ https://goo.gl/06T2nf A (very quiet) Discussion Group https://groups.google.com/forum/#!forum/softwaremetaphor https://goo.gl/k8Y4fi