What  am  I  talking  about?  Let’s  take  a  look  at  some  examples  

h<p://www.youtube.com/watch?v=HyA6UXi0v6g  

What  am  I  talking  about?    

h<p://xkcd.com/612/  

What  am  I  talking  about?    

h<p://www.youtube.com/watch?v=sxtYxIObjWg  

What  am  I  talking  about?    

h<p://www.youtube.com/watch?v=nfnM_8JBmmA  

What  am  I  talking  about?    

h<p://www.youtube.com/watch?v=apN0_NQrC0s  

What  do  all  these  examples  have  in  common?    

What  do  all  these  examples  have  in  common?    

What’s  so  special  about  it?  (from  a  user’s  perspec>ve)  

 

TIME   (aka  a  temporal  sequence  of  events)    

•  “HCI  impedance  mismatch”  (my  phrase)  –  user’s  ac.ons  are  too  fast  for  the  system,  system’s  responses  are  too  slow  for  the  user  

•  Without  immediate  feedback,  user  error  is  introduced—they  click  bu<ons  mul.ple  .mes,  try  to  swipe  mul.ple  .mes,  try  to  close  unresponsive  apps  even  if  they  are  not  actually  frozen,  poten.ally  leading  to  data  loss,  etc.  

•  When  things  don’t  work  smoothly,  users  are  reminded  that  they  are  “using  a  computer”,  sense  of  magic/fun  decreases,  sense  of  control  decreases,  frustra.on  increases  

•  Unresponsive  apps  violate  4  of  Nielsen’s  10  usability  heuris>cs  (Visibility  of  system  status,  match  with  real  world  (real  objects  don’t  stu<er/freeze),  user  control/freedom,  error  preven.on.)  

What’s  so  special  about  it?  (from  an  interac>on  designer’s  perspec>ve)  

 

TIME   (aka  a  temporal  sequence  of  events)    

•  Difficult  to  portray  .me-­‐sensi.ve  interac.ons  in  sta>c  mockups,  or  even  in  higher-­‐level  prototypes  

•  Time-­‐based  performance  characteris.cs  are  invisible  and  unpredictable,  which  makes  it  hard  to  iden.fy  them  as  “features”  or  “defects”  

•  UI  performance  considera.ons  are  largely  qualita>ve  in  nature  –  the  answer  to  the  ques.on  of  “what’s  good  enough?”  varies  widely  

•  Because  of  their  invisible  and  qualita.ve  nature,  UI  performance  characteris.cs  tend  to  rate  low  on  the  list  of  managers’  and  programmers’  priori.es  

What’s  so  special  about  it?  (from  a  soMware  developer’s  perspec>ve)  

 

TIME   (aka  a  temporal  sequence  of  events)    

•  Notoriously  difficult  to  handle  unpredictable  .me  values  in  code  –event/callback-­‐driven  asynchronous  programming  is  easy  to  screw  up  (or  is  avoided  due  to  fear  of  complexity,  lack  of  understanding)  •  Race  condi.ons  •  Error  handling  issues  •  “Feedback  loops”  •  Execu.ng  on  UI  thread  •  Asynchronous  APIs  are  harder  to  understand  and  debug  

•  Difficult  to  pin  down  sources  of  performance  issues  •  UI  toolkit  weaknesses  (e.g.  Flash,  HTML5)  •  Difficult  to  judge  real-­‐world  performance  characteris.cs  because  developers’  machines  tend  to  be  high-­‐spec’d  

So  what  can  we  do  about  it?  1.  Acknowledge  that  UI  performance  characteris.cs  are  a  key  

component  of  user  experience.  Designers  can’t  be  sa.sfied  with  sta.c  mockups  alone.  Developers  can’t  be  sa.sfied  with  simply  “looking  like”  a  design.  

2.  No  “designing  it  and  then  dropping  it  off  at  the  programmers’  feet”.  Designers  need  to  work  closely  with  developers  and  test  itera>ons  in  >ght  cycles—that’s  what  UCD  is  all  about!  

3.  Enough  >me  needs  to  be  devoted  to  fine-­‐tuning  UI  performance.  It  should  be  a  key  ongoing  task  for  developers  and  testers,  not  an  aqerthought.  

4.  Programmers  need  to  wrap  their  heads  around  asynchronous  APIs  and  event-­‐driven  programming,  if  they  haven’t  already.  

5.  In  cases  where  performance  can’t  be  directly  improved,  don’t  keep  the  user  wai>ng  –  show  some  kind  of  progress  indica.on,  use  cached  content  liberally,  and  don’t  block  the  UI  (thread)!    

Thanks  for  listening!  and  now  it’s  .me  for  some  Q&A  /  discussions!  

Michael  Klein  michaelklein27@gmail.com  h<p://gplus.to/michaelklein27  h<p://www.linkedin.com/in/michaelklein3  @mischkl  

Links  Jakob  Nielsen,  Response  Times:  The  3  Important  Limits  h<p://www.nngroup.com/ar.cles/response-­‐.mes-­‐3-­‐important-­‐limits/  

Jakob  Nielsen,  Website  Response  Times  h<p://www.nngroup.com/ar.cles/website-­‐response-­‐.mes/  

Steven  Seow,  Designing  and  Engineering  Time  (Book)  h<p://www.engineering.me.com  

Steven  Seow,  User  Interface  Timing  Cheatsheet  h<p://www.stevenseow.com/papers/UI%20Timing%20Cheatsheet.pdf  

GNOME  Human  Interface  Guidelines  2.2.2,  Characteris>cs  of  Responsive  Applica>ons  h<p://developer.gnome.org/hig-­‐book/3.5/feedback-­‐responsiveness.html