This document discusses user experience (UX) design through the lens of representational state transfer (REST) architectural principles. It argues that applying REST concepts like standardized interfaces, hypermedia, and resource-oriented design can help lower complexity and improve usability for users. The document examines examples like the iPhone and universal remote controls to show how RESTful approaches promote a better user experience (RUX) for common users compared to remote procedure call (RPC) styles that are better suited for power users. It advocates a pragmatic approach combining strategic use of REST principles with tactical use of RPC where needed.

1. “Restful User Experience”
Unconventional views on
user experience vs. architectural design
Wayne Lee, May 2009
http://trilancer.wordpress.com/

2. What is this all about?
To share
my humble opinions
on user experience designs with
insights from representational state transfer
studies as well as inspecting software architectural design
with user experience philosophy to improve overall system design …
Or simply put, to study
through
UX REST LENS
and
through
REST UX LENS
to better system designs
Image Source: http://www.flickr.com/photos/danielgreene/344196890/
http://www.flickr.com/photos/surstubben/475404411/

3. Background
• Representational state transfer (REST)
– A software architecture style for distributed
hypermedia systems, e.g., the World Wide Web
– Introduced by Roy Fielding in 2000
• User experience (UX)
– The overarching experience a person has as a result
of interactions with a product or service, its delivery,
and related artifacts, according to their design

4. The REST Triangle
[Post, Get, Put, Delete], Hypermedia: HTML, XML,
[Post, Get, Put, Delete], Hypermedia: HTML, XML,
Represe
[C R U D] … JSON, JPG, GIF …
[C R U D] … JSON, JPG, GIF …
Verbs
Constrained Set Constrained Set
ntations
Constrained Set Constrained Set
RESOURCES
Nouns
Universal URI, XRI …
Universal URI, XRI …
Unconstrained Set
Unconstrained Set

5. REST vs. RPC
• Resource-centric view • Command-centric view
– ONE uniform set of – Custom, unique sets of
methods (verbs) methods (verbs)
– Standard media types – Custom media types
– Lots resources (nouns) – Fewer objects (nouns)
– Some common knowledge – Prior specific knowledge
required to access ALL required to locate / access
resources each object

6. REST vs. SOAP
• REST simplicity = • WS-* Complexity =
freedom from choice freedom of choice
– 5 decisions to choose – 12 decisions to choose
among 16 alternatives among 32 alternatives
– 12 decisions already – 2 decisions already
taken (but 5 are DIY) taken (SOAP, WSDL +
XSD)
Source: http://www.jopera.org/docs/publications/2008/restws

7. UX through REST lens
Image Source: http://www.flickr.com/photos/mark_boucher/794747329/

8. UX Differences
in software architectural terms
l”
” tfu
PC es
“R “R
Press together to
lock / unlock
“Dumb Phone” iPhone
• Lots models, varying UX • Few models, consistent UX
• Lots buttons, with function overload • Few buttons, soft keys on-demand
• Various key-combinations to invoke lots • Few gestures (tap, flick, glide…) to
(sometimes mysterious) functions invoke ALL functions
Image Source: Nokia & Apple

9. iPhone Feature List …
Source: http://www.apple.com/iphone/

10. … aka “Sitemap”
/calendar /photos
/sms /maps
/youtube /weather
/stocks
/notes
Home
/calc
/itunes /apps
/phone /ipod
/sms /safari

11. Conceptual Restful State Machine of iPhone
i.e., web browsing mentality can be mapped smoothly
/phone/favorites /phone/favorites/Jerry
/phone/contacts/Tom
/phone/contacts Call (submit)
/phone
/phone/keypad /phone/call
Dial (form input)  Call (submit) End Call
/phone/voicemail /phone/voicemail/Emily Call Back (submit)
Delete
/phone/reschedule
State Transitions Explained with REST
Create a new call
/calendar POST /phone/call
Call session resource
Destroy current
DELETE /phone/call
End Call
call session
/mail Redirect back to
state before call

12. The iPhone Triangle
[Tap, Glide, Flick, Pinch, CoverFlow, List, Icon,
[Tap, Glide, Flick, Pinch, CoverFlow, List, Icon,
Represe
Rotate, Swing … ] ] Map, Table, Player …
Rotate, Swing … Map, Table, Player …
Verbs
Constrained Set Constrained Set
ntations
Constrained Set Constrained Set
Nouns
Events, SMS, Mails, Photos,
Events, SMS, Mails, Photos,
Songs, Videos, Apps …
Songs, Videos, Apps …
Unconstrained Set
Unconstrained Set

13. Restful User Experience (RUX)
UNIFORM STANDARDIZED
UNIFORM STANDARDIZED
Represe
buttons //commands // Info presentation
buttons commands Info presentation
Verbs
ntations
gestures … layouts //views
gestures … layouts views
Nouns
UNLIMITED
UNLIMITED
Volume of content
Volume of content
indexed or hyperlinked
indexed or hyperlinked

14. Further RUX Example – Universal Remote Control
• One-Touch Control
• Up to 15 components: video,
audio, & gaming
• Compatibility: supports 5,000+
brands & 225,000 devices
Logitech Harmony 1000 Advanced Universal Remote
Source: http://www.logitech.com/index.cfm/remotes/universal_remotes/devices/373&cl=US,EN

15. Different Approaches to Universal Remote Control, aka
RUX vs. RPC-UX
15 Devices
VS
Logitech Harmony 1000
5 Devices 8 Devices
16 Devices
Sony RM-AX4000A Logitech Harmony 510 Sony RMVL610B
for common users for power users
Image Source: Sony & Logitech

16. RUX or RPC-UX?
aka, REST or RPC
Image Source: http://deadthingsdontfly.deviantart.com/art/thisway-thatway-72119766

17. freedom of choice freedom from choice
4+ 10+
3
Models
14 10
Models
4
Models
Models
Models
Models
12 (color variation included)
Models / Series
Source: http://www.electronista.com/articles/08/06/30/rbc.high.iphone.demand/

18. iPhone Takes 2/3 of Mobile Market
Source: http://blog.concentricsky.com/2009/03/iphone-takes-23-of-mobile-market/

19. Implications
• Market suggests RUX popularity
– Device / application with lots “nouns” in usage scenarios better adopt
RUX to ease user access
– RPC-UX still works with limited nouns, but potential extensibility greatly
hindered by e.g., physical shape
• iPhone resembles web browsing experiences
– If you can surf the Web, you can use an iPhone
– If you can’t “surf” a phone, you won’t use it to surf the Web
• Less choices + good design = good business
UX through REST lens

20. REST through UX lens
Image Source: http://www.flickr.com/photos/valpopando/2787823568/

21. Less is More (More or Less):
Uncommon Sense and the Design of Computers
System Functionality vs. Human System Strength vs. Generality
y
alit
on
ti
nc
Fu
of Example: Potato Peeler
th
row (Can do FEW things BETTER than others)
G
Strength
Strong
Growth of Human Capability
Example: Generic Kitchen Knife Specific
(Can do LOTS things, but NOT optimized) System
Threshold of Frustration
a.k.a.
“Complexity Barrier” Weak General System
Generality
Source: http://www.billbuxton.com/LessIsMore.html

22. Software Architecture Design
through “less is more” lens
System Functionality vs. Human System Strength vs. Generality
• SOA
• “Smartphone”
which demand
lity RPC systems, Dedicated client
na really smart user
tio
nc Specific Remote Control…
Fu
Strength
Strong
Human Capability
Restful systems, Web browser Specific
Universal Remote Control… System
• Web dev
• iPhone
Weak General System
Generality
The theories hold true for developers & users alike …

23. A Strong AND General System?
a.k.a., integrated set of strong specific systems
Unlikely – “Net Benefit” –
Due to “threshold of frustration” from high A theoretical solution from Buxton about
cognitive load in design & use digital and networked devices …
Strength
Strength
Cognitive Load
“Net Benefit”
Threshold of Frustration
Generality
Generality
Net Benefit: devices communicate & cooperate with each other, thereby
assuming much of the load that would otherwise burden the user …
Source: http://www.billbuxton.com/LessIsMore.html

24. Approaches to “Net Benefit”
in Software Systems Integration
Solution A:
Unlikely
Solution A:
Intelligence in each system to enable
Intelligence in each system to enable
due to even more
automatic communication & collaboration
automatic communication & collaboration
complexity therein
between systems … aka. Magic
between systems … aka. Magic
Solution B:
Feasible
Solution B:
Apply principles, standardization,
Apply principles, standardization,
Apply “less is more”
simplification, unification & specifications…
simplification, unification & specifications…
for greater good
aka. Design Constraints
aka. Design Constraints

25. Less is More
The world wide web works by design, not magic
• Few verbs
Whole universe of knowledge
REST • A few MIME types
only clicks away
• Uniform resource URI
Image: 3D Map of World Wide Web from www.opte.org

26. More or Less?
Situations where RPC works way better …
Strong Specific System Weak General System
Looking for a Presenter?
Handy & efficient Overkill & inconvenient
Source: http://www.logitech.com/index.cfm/remotes/presentation_remote/devices/175&cl=us,en

27. More or Less?
… and REST works positively terribly
Try playing piano in a browser or on an iPhone all day …
Source: http://www.daniellaberge.com/music/webpiano/webpiano1.htm
http://moocowmusic.com/

28. REST or RPC?
aka, RUX or RPC-UX
Image Source: http://deadthingsdontfly.deviantart.com/art/thisway-thatway-72119766

29. RUX vs. RPC-UX versus REST vs. RPC
RPC-UX RUX
• Direct & Efficient • Lower “cognitive load” working with
Pros large complex systems
• High “cognitive load” operating large • Indirect / inefficient for responsive /
Cons complex systems repetitive tasks
• Fits specific command-&-control tasks • Fits general tasks
Conclusion • Good for power users, professionals … • Good for common users, info seekers…
RPC REST
• Optimized for specific task • Low technical barrier to entry
Pros • Fine-grained control • Massively extensible / scalable
• Hidden status & implicit semantics • Performance penalty, hard to customize
Cons • Complicated testing & debugging • Coarse-grained control
• Fits proprietary mission-critical apps • Fits open resource-oriented apps
Conclusion • Costly planning & implementation • Easier planning & implementation

30. UX Classification of iPhone Apps
RPC-UX RUX
QuickVoice Recorder
BrainTeaser Kindle for iPhone
FedEx Mobile
quot;Purequot; RPC-UX
quot;Purequot; RUX
RPC REST
A given system is usually a balanced combination of
RPC-UX & RUX, aka RPC & REST

31. “Pure” RPC vs. “Pure” REST
Difference in Aggregated Complexity
V R V R
N N
# of systems integrated
V – Verbs (method)
R – Representations (media)
Low High
N – Nouns (object, resource)

32. A Pragmatic Architectural Approach
for
Large Scale System Integration
V R
A REST “Core” Some RPC “Deviations”
• Governing constraints • Local architecture & principles
ARCHITECT
• Uniform interfaces & views • Special methods or layouts
• Mitigated overall complexity • Optimized local performance
DEVELOPER
• Clearer global design • Optimized local design
• Minimized cognitive load • Optimized local operation
USER
• Assured common user access • Convenience for power users
N

33. The Pragmatic Architectural Approach to
Realize “Net Benefit”
Tactic Use of RPC (RPC-UX):
Tactic Use of RPC (RPC-UX):
Strong Specific Approach
Specific command, custom configuration,
Local Specific command, custom configuration,
To strengthen specific tasks
non-standard interface, proprietary layout…
non-standard interface, proprietary layout…
Deviance and power users
To optimize specific local designs
To optimize specific local designs
+ + +
Strategic Use of REST (RUX):
Strategic Use of REST (RUX):
Weak General Approach
Architectural constraints, standardization,
Global Architectural constraints, standardization,
For common user access with
simplification, convention over configuration…
simplification, convention over configuration…
Uniformity minimized cognitive load
To mitigate overall complexity for design
To mitigate overall complexity for design

34. The Result – A Hybrid System
Actual System Cognitive Load
Strength & Generality Perceived by User
Strong specific features atop
Strength
Strength
Threshold of Frustration
“Net Benefit” foundation
Generality
Generality

35. Implications
• Complexity should be a decisive factor in architectural design
– For small & simple systems, either RPC or REST will work
– For large complex system integration: Strategic use of REST + Tactic
use of RPC recommended
• An actual system architecture should be a reasonable balance of
REST + RPC, according to usage nature
• Always fight complexity with Architectural Wisdom, not prayers for
miracle
REST through UX lens

36. Last Not Least
Always Picture Your System First …
Your
System

37. References
• Roy T. Fielding’s DISSERTATION
– Architectural Styles and the Design of Network-based Software Architectures
• Wikipedia:
– http://en.wikipedia.org/wiki/Representational_State_Transfer
– http://en.wikipedia.org/wiki/User_experience
• Bill Buxton:
– http://www.billbuxton.com/LessIsMore.html
• iPhone App Store
– http://www.apple.com/iphone/appstore/

38. “Everything should be made as
simple as possible, but not simpler.”
Image Source: http://en.wikipedia.org/wiki/File:Albert_Einstein_portrait.jpg