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3/20/2014 Affordances http://localhost:9090/onepage 1/67 Affordances in Programming Languages Randy Coulman Principal Software Engineer http://randycoulman.com @randycoulman randycoulman

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3/20/2014 Affordances http://localhost:9090/onepage 2/67 Satu Kyröläinen ­ http://www.satukyrolainen.com/affordances/

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3/20/2014 Affordances http://localhost:9090/onepage 3/67 Satu Kyröläinen ­ http://www.satukyrolainen.com/affordances/

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3/20/2014 Affordances http://localhost:9090/onepage 4/67 Affordance A quality of an object or environment that allows someone to perform an action.

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3/20/2014 Affordances http://localhost:9090/onepage 5/67 Nicolas Nova ­ http://www.flickr.com/photos/nnova/2252222949/

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3/20/2014 Affordances http://localhost:9090/onepage 6/67 William Lindeke ­ http://tcsidewalks.blogspot.com/2009/06/signs­of­times­14.html

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3/20/2014 Affordances http://localhost:9090/onepage 7/67 Yoni Alter ­ http://www.yoniishappy.com/Tube­escalators

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3/20/2014 Affordances http://localhost:9090/onepage 8/67 Affordances and Software

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3/20/2014 Affordances http://localhost:9090/onepage 9/67 Amir Rajan (@amirrajan) Coding Out Loud ­ REST APIs series http://vimeo.com/channels/659338

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3/20/2014 Affordances http://localhost:9090/onepage 10/67 Example Points Smalltalk ­> Ruby

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3/20/2014 Affordances http://localhost:9090/onepage 11/67 c l a s s P o i n t d e f i n i t i a l i z e ( x , y ) @ x = x @ y = y e n d e n d P o i n t . n e w ( 3 , 4 )

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3/20/2014 Affordances http://localhost:9090/onepage 12/67 http://images.cryhavok.org/d/25562­2/Polar+and+Cartesian+Bears.jpg

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3/20/2014 Affordances http://localhost:9090/onepage 13/67 θ r sinθ r cosθ r x y http://upload.wikimedia.org/wikipedia/commons/7/78/Polar_to_cartesian.svg

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3/20/2014 Affordances http://localhost:9090/onepage 14/67 c l a s s P o i n t d e f i n i t i a l i z e ( x , y ) @ x = x @ y = y e n d e n d P o i n t . n e w ( 3 , 4 )

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3/20/2014 Affordances http://localhost:9090/onepage 15/67 P o i n t c l a s s > > x : a n X y : a Y ^ s e l f n e w i n i t i a l i z e X : a n X y : a Y P o i n t > > i n i t i a l i z e X : a n X y : a Y x : = a n X . y : = a Y P o i n t x : 3 y : 4

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3/20/2014 Affordances http://localhost:9090/onepage 16/67 P o i n t c l a s s > > r : r a d i u s t h e t a : a n g l e I n R a d i a n s ^ s e l f x : r a d i u s * a n g l e I n R a d i a n s c o s y : r a d i u s * a n g l e I n R a d i a n s s i n P o i n t r : 5 t h e t a : 0 . 9 2 7 2 9 5

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3/20/2014 Affordances http://localhost:9090/onepage 17/67 Affordance Named Constructors

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3/20/2014 Affordances http://localhost:9090/onepage 18/67 c l a s s P o i n t d e f s e l f . x y ( x , y ) n e w ( x , y ) e n d d e f s e l f . p o l a r ( r , t h e t a ) x y ( r * M a t h . c o s ( t h e t a ) , r * M a t h . s i n ( t h e t a ) ) e n d p r i v a t e _ c l a s s _ m e t h o d : n e w # . . . r e s t s a m e a s b e f o r e e n d P o i n t . x y ( 3 , 4 ) P o i n t . p o l a r ( 5 , 0 . 9 2 7 2 9 5 )

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3/20/2014 Affordances http://localhost:9090/onepage 19/67 Example Find/Detect Smalltalk ­> Ruby

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3/20/2014 Affordances http://localhost:9090/onepage 20/67 # ( 2 4 6 8 ) d e t e c t : [ : e a c h | e a c h o d d ] " U n h a n d l e d e x c e p t i o n : E l e m e n t N o t F o u n d "

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3/20/2014 Affordances http://localhost:9090/onepage 21/67 [ 2 , 4 , 6 , 8 ] . f i n d { | n | n . o d d ? } # = > n i l

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3/20/2014 Affordances http://localhost:9090/onepage 22/67 # ( 2 4 6 8 ) d e t e c t : [ : e a c h | e a c h o d d ] i f N o n e : [ # n o n e ] " # n o n e "

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3/20/2014 Affordances http://localhost:9090/onepage 23/67 Affordance Multiple Blocks

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3/20/2014 Affordances http://localhost:9090/onepage 24/67 [ 2 , 4 , 6 , 8 ] . f i n d ( - > { : n o n e } ) { | n | n . o d d ? } # = > : n o n e

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3/20/2014 Affordances http://localhost:9090/onepage 25/67 Linguistic Relativity a.k.a. The Sapir­Whorf Hypothesis "[T]he structure of a language affects the ways in which its respective speakers conceptualize their world ... or otherwise influences their cognitive processes." ­­ http://en.wikipedia.org/wiki/Linguistic_relativity

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3/20/2014 Affordances http://localhost:9090/onepage 26/67 When Code Cries Cory Foy at SCNA 2012 http://vimeo.com/53986875 What does a language allow you to say? What does a language force you to say?

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3/20/2014 Affordances http://localhost:9090/onepage 27/67 The Power and Philsophy of Ruby Matz at OSCON 2003 http://www.rubyist.net/~matz/slides/oscon2003/mgp00001.html "Languages are not only tools to communicate, but also tools to think."

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3/20/2014 Affordances http://localhost:9090/onepage 28/67 Example Cleaning Up After Yourself C++ ­> Ruby

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3/20/2014 Affordances http://localhost:9090/onepage 29/67 i f ( ( e r r = S S L F r e e B u f f e r ( & h a s h C t x ) ) ! = 0 ) g o t o f a i l ; i f ( ( e r r = R e a d y H a s h ( & S S L H a s h S H A 1 , & h a s h C t x ) ) ! = 0 ) g o t o f a i l ; i f ( ( e r r = S S L H a s h S H A 1 . u p d a t e ( & h a s h C t x , & c l i e n t R a n d o m ) ) ! = g o t o f a i l ; i f ( ( e r r = S S L H a s h S H A 1 . u p d a t e ( & h a s h C t x , & s e r v e r R a n d o m ) ) ! = g o t o f a i l ; i f ( ( e r r = S S L H a s h S H A 1 . u p d a t e ( & h a s h C t x , & s i g n e d P a r a m s ) ) ! = g o t o f a i l ; g o t o f a i l ; i f ( ( e r r = S S L H a s h S H A 1 . f i n a l ( & h a s h C t x , & h a s h O u t ) ) ! = 0 ) g o t o f a i l ; / / . . . f a i l : S S L F r e e B u f f e r ( & s i g n e d H a s h e s ) ; S S L F r e e B u f f e r ( & h a s h C t x ) ; r e t u r n e r r ;

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3/20/2014 Affordances http://localhost:9090/onepage 30/67 # i n c l u d e " s u p p o r t . h " # i n c l u d e < i o s t r e a m > v o i d f o o ( ) { R e s o u r c e * r e s o u r c e = a c q u i r e R e s o u r c e ( ) ; b a r ( r e s o u r c e ) ; i f ( b a z ( r e s o u r c e ) ! = 4 2 ) r e t u r n ; s t d : : c o u t < < " C o m p l e t e d s u c c e s s f u l l y ! " < < s t d : : e n d l ; r e l e a s e R e s o u r c e ( r e s o u r c e ) ; }

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3/20/2014 Affordances http://localhost:9090/onepage 31/67 $ . / b r o k e n A c q u i r i n g r e s o u r c e C a u g h t e x c e p t i o n : o o p s !

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3/20/2014 Affordances http://localhost:9090/onepage 32/67 # i n c l u d e " s u p p o r t . h " # i n c l u d e < i o s t r e a m > v o i d f o o ( ) { R e s o u r c e * r e s o u r c e = a c q u i r e R e s o u r c e ( ) ; t r y { b a r ( r e s o u r c e ) ; i f ( b a z ( r e s o u r c e ) = = 4 2 ) { s t d : : c o u t < < " C o m p l e t e d s u c c e s s f u l l y ! " < < s t d : : e n d l ; } } c a t c h ( s t d : : e x c e p t i o n & e ) { r e l e a s e R e s o u r c e ( r e s o u r c e ) ; t h r o w ; } r e l e a s e R e s o u r c e ( r e s o u r c e ) ; }

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3/20/2014 Affordances http://localhost:9090/onepage 33/67 $ . / w o r d y A c q u i r i n g r e s o u r c e R e l e a s i n g r e s o u r c e C a u g h t e x c e p t i o n : o o p s !

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3/20/2014 Affordances http://localhost:9090/onepage 34/67 # i n c l u d e " s u p p o r t . h " # i n c l u d e < i o s t r e a m > v o i d f o o ( ) { R e s o u r c e * r e s o u r c e = a c q u i r e R e s o u r c e ( ) ; t r y { b a r ( r e s o u r c e ) ; i f ( b a z ( r e s o u r c e ) = = 4 2 ) { s t d : : c o u t < < " C o m p l e t e d s u c c e s s f u l l y ! " < < s t d : : e n d l ; } } c a t c h ( s t d : : e x c e p t i o n & e ) { r e l e a s e R e s o u r c e ( r e s o u r c e ) ; t h r o w ; } r e l e a s e R e s o u r c e ( r e s o u r c e ) ; }

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3/20/2014 Affordances http://localhost:9090/onepage 35/67

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3/20/2014 Affordances http://localhost:9090/onepage 36/67 RAII Resource Acquisition Is Initialization Acquire resources in the constructor Release them in the destructor

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3/20/2014 Affordances http://localhost:9090/onepage 37/67 # i n c l u d e " S a f e R e s o u r c e . h " # i n c l u d e " s u p p o r t . h " S a f e R e s o u r c e : : S a f e R e s o u r c e ( ) : r e s o u r c e ( a c q u i r e R e s o u r c e ( ) ) { } S a f e R e s o u r c e : : ~ S a f e R e s o u r c e ( ) { r e l e a s e R e s o u r c e ( r e s o u r c e ) ; } R e s o u r c e * S a f e R e s o u r c e : : g e t ( ) { r e t u r n r e s o u r c e ; }

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3/20/2014 Affordances http://localhost:9090/onepage 38/67 # i n c l u d e " S a f e R e s o u r c e . h " # i n c l u d e " s u p p o r t . h " # i n c l u d e < i o s t r e a m > v o i d f o o ( ) { S a f e R e s o u r c e r e s o u r c e ; b a r ( r e s o u r c e . g e t ( ) ) ; i f ( b a z ( r e s o u r c e . g e t ( ) ) ! = 4 2 ) r e t u r n s t d : : c o u t < < " C o m p l e t e d s u c c e s s f u l l y ! " < < s t d : : e n d l ; }

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3/20/2014 Affordances http://localhost:9090/onepage 39/67 $ . / r a i i A c q u i r i n g r e s o u r c e R e l e a s i n g r e s o u r c e C a u g h t e x c e p t i o n : o o p s !

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3/20/2014 Affordances http://localhost:9090/onepage 40/67 Affordance Deterministic Destructors

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3/20/2014 Affordances http://localhost:9090/onepage 41/67 Ruby doesn't have deterministic destructors. So what can we do instead?

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3/20/2014 Affordances http://localhost:9090/onepage 42/67 Blocks!

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3/20/2014 Affordances http://localhost:9090/onepage 43/67 c l a s s S a f e R e s o u r c e d e f s e l f . a c q u i r e r e s o u r c e = s e l f . n e w y i e l d r e s o u r c e e n s u r e r e s o u r c e . r e l e a s e e n d d e f i n i t i a l i z e p u t s " A c q u i r i n g r e s o u r c e " @ r e s o u r c e = O b j e c t . n e w e n d d e f r e l e a s e p u t s " R e l e a s i n g r e s o u r c e " @ r e s o u r c e = n i l e n d

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3/20/2014 Affordances http://localhost:9090/onepage 44/67 r e q u i r e _ r e l a t i v e " s u p p o r t " r e q u i r e _ r e l a t i v e " s a f e _ r e s o u r c e " d e f f o o S a f e R e s o u r c e . a c q u i r e d o | r e s o u r c e | b a r ( r e s o u r c e ) r e t u r n u n l e s s b a z ( r e s o u r c e ) = = 4 2 p u t s " C o m p l e t e d s u c c e s s f u l l y ! " e n d e n d

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3/20/2014 Affordances http://localhost:9090/onepage 45/67 $ r u b y d r i v e r . r b A c q u i r i n g r e s o u r c e R e l e a s i n g r e s o u r c e C a u g h t e x c e p t i o n : o o p s !

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3/20/2014 Affordances http://localhost:9090/onepage 46/67 Example ImageReader Smalltalk ­> Ruby

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3/20/2014 Affordances http://localhost:9090/onepage 47/67 I m a g e R e a d e r c l a s s > > f r o m F i l e : a F i l e n a m e | r e a d e r C l a s s i m a g e S t r e a m r e a d e r | i m a g e S t r e a m : = a F i l e n a m e r e a d S t r e a m b i n a r y . [ r e a d e r C l a s s : = s e l f r e a d e r C l a s s F o r : i m a g e S t r e a m . r e a d e r C l a s s i f N i l : [ ^ s e l f e r r o r : ' U n k n o w n i m a g e t y p e : ' , a F i l e n a m e a s S t r i n g ] . r e a d e r : = r e a d e r C l a s s o n : i m a g e S t r e a m ] e n s u r e : [ i m a g e S t r e a m c l o s e ] . ^ r e a d e r

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3/20/2014 Affordances http://localhost:9090/onepage 48/67 I m a g e R e a d e r c l a s s > > r e a d e r C l a s s F o r : i m a g e S t r e a m ^ s e l f s u b c l a s s e s d e t e c t : [ : e a c h C l a s s | i m a g e S t r e a m r e s e t . [ e a c h C l a s s c a n R e a d : i m a g e S t r e a m ] e n s u r e : [ i m a g e S t r e a m r e s e t ] ] i f N o n e : [ n i l ]

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3/20/2014 Affordances http://localhost:9090/onepage 49/67 Affordance Subclass Iteration

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3/20/2014 Affordances http://localhost:9090/onepage 50/67 c l a s s I m a g e R e a d e r d e f s e l f . r e a d ( f i l e n a m e ) F i l e . o p e n ( f i l e n a m e , " r b " ) d o | i o | r e a d e r _ c l a s s = f i n d _ r e a d e r _ c l a s s ( i o ) r a i s e " U n k n o w n i m a g e t y p e : # { f i l e n a m e } " u n l e s s r e a d e r _ c l a s s r e a d e r _ c l a s s . n e w ( i o ) e n d e n d # . . . e n d

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3/20/2014 Affordances http://localhost:9090/onepage 51/67 c l a s s I m a g e R e a d e r # . . . d e f s e l f . f i n d _ r e a d e r _ c l a s s ( i o ) s u b c l a s s e s . f i n d { | r e a d e r | b e g i n i o . r e w i n d r e a d e r . c a n _ r e a d ? ( i o ) e n s u r e i o . r e w i n d e n d } e n d # . . . e n d

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3/20/2014 Affordances http://localhost:9090/onepage 52/67 c l a s s I m a g e R e a d e r # . . . d e f s e l f . i n h e r i t e d ( s u b c l a s s ) s u b c l a s s e s < < s u b c l a s s e n d d e f s e l f . s u b c l a s s e s @ s u b c l a s s e s | | = [ ] e n d # . . . e n d

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3/20/2014 Affordances http://localhost:9090/onepage 53/67 c l a s s B M P I m a g e R e a d e r < I m a g e R e a d e r d e f s e l f . c a n _ r e a d ? ( i o ) i o . r e a d ( 2 ) = = " B M " e n d d e f r e a d _ i m a g e p u t s " R e a d i n g B M P " e n d e n d

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3/20/2014 Affordances http://localhost:9090/onepage 54/67 c l a s s J P G I m a g e R e a d e r < I m a g e R e a d e r d e f s e l f . c a n _ r e a d ? ( i o ) i o . r e a d ( 2 ) = = " \ x F F \ x D 8 " . b e n d d e f r e a d _ i m a g e p u t s " R e a d i n g J P G " e n d e n d

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3/20/2014 Affordances http://localhost:9090/onepage 55/67 c l a s s P N G I m a g e R e a d e r < I m a g e R e a d e r d e f s e l f . c a n _ r e a d ? ( i o ) i o . r e a d ( 8 ) = = " \ x 8 9 P N G \ r \ n \ x 1 A \ n " . b e n d d e f r e a d _ i m a g e p u t s " R e a d i n g P N G " e n d e n d

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3/20/2014 Affordances http://localhost:9090/onepage 56/67 r e q u i r e _ r e l a t i v e " i m a g e _ r e a d e r s " % w { b m p j p g p n g } . e a c h d o | e x t | I m a g e R e a d e r . r e a d ( " e x a m p l e . # { e x t } " ) e n d

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3/20/2014 Affordances http://localhost:9090/onepage 57/67 $ r u b y s u b c l a s s e s . r b R e a d i n g B M P R e a d i n g J P G R e a d i n g P N G

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3/20/2014 Affordances http://localhost:9090/onepage 58/67 Takeaways

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3/20/2014 Affordances http://localhost:9090/onepage 59/67 Languages afford certain designs and inhibit others

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3/20/2014 Affordances http://localhost:9090/onepage 60/67 Languages influence thought

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3/20/2014 Affordances http://localhost:9090/onepage 61/67 Learning new languages will increase your "solution space"

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3/20/2014 Affordances http://localhost:9090/onepage 62/67 Don't go too far

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3/20/2014 Affordances http://localhost:9090/onepage 63/67 Want More? http://randycoulman.com/blog/categories/affordances/

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3/20/2014 Affordances http://localhost:9090/onepage 64/67 Acknowledgements Key Technology (http://www.key.net/) Rogue.rb (@roguerb) Jen Myers (@antiheroine)

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3/20/2014 Affordances http://localhost:9090/onepage 65/67 References The Design of Every Day Things ­ Donald Norman Coding Out Loud ­ Amir Rajan Linguistic Relativity ­ Wikipedia article When Code Cries ­ Cory Foy at SCNA 2012 The Power and Philosophy of Ruby ­ Matz at OSCON 2003

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3/20/2014 Affordances http://localhost:9090/onepage 66/67 Questions?

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3/20/2014 Affordances http://localhost:9090/onepage 67/67 Randy Coulman http://speakerrate.com/randycoulman http://www.slideshare.net/randycoulman http://randycoulman.com @randycoulman randycoulman