Whether you're creating a complex web application or a simple library, everything you create has a user. Why, then, do we concentrate on our users when developing a user interface, but so often forget them when developing APIs? In this talk, Christopher presents a whirlwind overview of a variety of different User Experience considerations when designing your APIs.

1. Your API is a UIChristopher Hoult

2. Your API is a UI @choult
Who is this guy?
“We’re Hiring”
Previously...

3. I also act
Credit: Richard Brown

4. YMMV
http://bit.ly/1yvvYb5

5. Your API is a UI @choult
What is a UI?
A “space where interactions between humans and
machines occur. The goal of this interaction is effective
operation and control of the machine on the user’s end,
and feedback from the machine, which aids the operator
in making operational decisions.”
Wikipedia

6. Your API is a UI @choult
What is an API?
“An application programming interface (API) specifies
a software component in terms of its operations, their
inputs and outputs and underlying types. Its main
purpose is to define a set of functionalities that are
independent of their respective implementation, allowing
both definition and implementation to vary without
compromising each other.”
Wikipedia

7. Users
http://bit.ly/1DMivvR

8. Your API is a UI @choult
Who are your users?
• Developers
• Colleagues
• Customers
• Their Customers
• Applications

9. Your API is a UI @choult
What does your API do?
• Real use cases
• User stories
• Document usage/flow
• Sell your API

10. Your API is a UI @choult
What can users do?
• Why are you exposing an API?
• It’s very rare to expose everything
• Too much complexity -> confusion
• Define restrictions
• Validate user stories against goals

11. Your API is a UI @choult
API Hierarchy of Needs
APIUX.com: http://bit.ly/Zl8Exo

12. Usability
http://bit.ly/1DWUcva

13. Your API is a UI @choult
Consistency
• Improves comfort for user
• Style guide (PSR-1/2; REST etc.)
• Common attributes/functions
• Naming
• Error codes

14. Your API is a UI @choult
Patterns
• Users understand Patterns
• Patterns aid understanding
• Webservices: RPC, REST
• Code: Gang of Four etc.

15. Your API is a UI @choult
Information Hierarchy
• Define ERM
• Arrange entry points from user POV
• Nesting entities can be problematic
• Get it right: classes and objects intuitive

16. Your API is a UI @choult
Abstraction
• User stories guide API design
• Hide complexity
• Avoid adhering to underlying model
• Do the hard work so users don’t have to

17. Your API is a UI @choult
Simplicity
• Best result of abstraction
• More straightforward, more use
• Smaller footprint = fewer failure paths
• Easy fault detection

18. Your API is a UI @choult
Extensibility
• Flipside to abstraction
• How will users extend codebase?
• Restrict as required - public/protected/private
• Take care - hard to retract public
• Patterns help here!

19. Functionality
& Reliability
http://bit.ly/109m7bG
(Oh, so he does do colour!)

20. Your API is a UI @choult
Testing
• Use appropriate testing methodology
• Make part of build/release process
• Monitor production with live testing
• Consider record/replay testing
• Regression testing

21. Your API is a UI @choult
Metrics
• Metrics tell you what is happening
• Record status codes
• Calibrate with normal running
• Insight into running code
• Graphite/statsd

23. Your API is a UI @choult
Logging
• Tells you what happened
• Helps debug production faults
• Reference in error messages
• Insight into running applications
• Information for users of code

24. Your API is a UI @choult
Versioning
• Plan versioning upfront
• Define upgrade/deprecation strategy
• What is a breaking change?
• How long will API be supported?
• Communicate with users

25. Your API is a UI @choult
Feedback
• Clear feedback
• Reasons for failure
• Appropriate language
• Error codes
• Normalized; human readable
• Provide glossary

26. Proficiency
http://bit.ly/1rJmLHJ

27. Your API is a UI @choult
Documentation
• No such thing as “self-documenting code”
• Write fulsome documentation
• Include working examples
• Cross-link from code
• Manuals, Quick Start Guides, Cookbooks

28. Your API is a UI @choult
Living Documentation
• Docblocks (Javadoc/PHPdoc) are a good start
• Cross-language (eg Doxygen)
• Use standards like PSR 5
• Annotations
• Interactive documentation - eg. IODocs

29. Your API is a UI @choult
Support / Community
• Define channels of communication
• Define location for participation
• Invite feedback
• Invite contribution - define guidelines
• Respond gracefully and attentively
• Learn from your users

30. Creativity
http://bit.ly/109m7bG

31. Your API is a UI @choult
<Inspirational Title>
• Flexibility
• Extensibility
• Serendipity
• Outreach
• Encouragement

32. Pragmatism
http://bit.ly/1votyWc

33. Your API is a UI @choult
On Pragmatism
• Pragmatism is good!
• Can promote technical debt
• Find a balance - RESTlike, RPCish
• Be realistic
• Iterate - versioning and deprecation

34. Take Pride
http://bit.ly/1xCeQ1W

35. Your API is a UI @choult
Your API is You!
• Like your UI, your API is your public face
• It is your avatar
• Take pride in your work
• Impress your users with its awesomeness!

36. Questions?
http://bit.ly/1npSVI6

37. Your API is a UI @choult
Thank you!
@choult
christopherhoult
chris@choult.com@
This presentation was typeset in HandTIMES and Open Sans, using Adobe InDesign CS6
(because I’m a lunatic)
Feedback please! https://joind.in/13392

38. Your API is a UI @choult
Resources / Inspiration
10 User Interface Design Fundamentals - Kyle Sollenberger
http://blog.teamtreehouse.com/10-user-interface-design-fundamentals
APIUX: API Hierarchy of Needs
http://apiux.com/2013/05/29/api-hierarchy-needs/
5 Golden Rules for Great Web API Design - Jordan Ambra
http://www.toptal.com/api-developers/5-golden-rules-for-designing-a-great-web-api