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S A R A H M E I W D C N Z 2 0 1 5 I S Y O U R C O D E TO O S O L I D ? https://www.flickr.com/photos/pie4dan/4567311801

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DevMynd S A R A H M E I C H I E F C O N S U LTA N T D E V M Y N D U N I T E D S TAT E S C H I E F O F BA L D E A G L E S A N D F R E E D O M http://world-map1.org/map1520769_0_0.htm http://www.coolholidaygraphics.com/flagday/glittergraphics/flagdayglitter2.gif https://www.devmynd.com/images/team/sarah-mei-cutout.png

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DevMynd

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C O D E BA S E S I WO R K O N N O R M A L C O D E BA S E S https://www.flickr.com/photos/pmarkham/5361277692

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AT F I R S T https://www.flickr.com/photos/jakerust/16661140289/

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https://www.flickr.com/photos/123638374@N08/14184697490

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https://www.flickr.com/photos/123638374@N08/14184697490

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DevMynd https://twitter.com/tenderlove/status/573907559871971328

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DevMynd https://twitter.com/tenderlove/status/573907559871971328

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DevMynd S A N D I M E T Z E X P E RT AT E V E RY T H I N G S E R I O U S LY, G E T I T A M A Z I N G B O O K http://www.sandimetz.com/ http://www.poodr.com/

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DevMynd S A N D I M E T Z E X P E RT AT E V E RY T H I N G S E R I O U S LY, G E T I T A M A Z I N G B O O K http://www.sandimetz.com/ http://www.poodr.com/

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D E S I G N D E C I D I N G H OW TO A R R A N G E C O D E https://www.flickr.com/photos/matley0/3616669592

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D E S I G N D E C I D I N G H OW TO A R R A N G E C O D E https://www.flickr.com/photos/matley0/3616669592

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O B J E C T- O R I E N T E D D E S I G N G R O U P I N G R E L AT E D F U N C T I O N A L I T Y I N O B J E C T S https://www.flickr.com/photos/mwanasimba/2901201955/

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DevMynd A L A N G UA G E F E AT U R E A WAY O F T H I N K I N G O B J E C T- O R I E N T E D D E S I G N I S https://www.flickr.com/photos/56627607@N05/15635620289/

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DevMynd A L A N G UA G E F E AT U R E A WAY O F T H I N K I N G O B J E C T- O R I E N T E D D E S I G N I S A D E S T I N AT I O N A M E A N S TO A N E N D https://www.flickr.com/photos/56627607@N05/15635620289/

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https://www.flickr.com/photos/redvers/532076662/

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https://www.flickr.com/photos/redvers/532076662/

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H I G H L OW H I G H L OW C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E

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H I G H L OW H I G H L OW C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E

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H I G H L OW H I G H L OW Procedures C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E

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H I G H L OW H I G H L OW Procedures C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E

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CalendarParamMgr GetCalendarIndex CalendarRouteResolver CalendarRouteResolverFactory RouteResolver RouteReceiver

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H I G H L OW H I G H L OW Procedures Set of Small Objects C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E

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H I G H L OW H I G H L OW Procedures ⚠⚡ Set of Small Objects C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E

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H I G H L OW H I G H L OW Procedures Set of Small Objects C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E Really big objects

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H I G H L OW H I G H L OW Procedures Set of Small Objects C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E Really big objects The wrong set of small objects

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H I G H L OW H I G H Procedures Set of Small Objects L OW C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E Really big objects The wrong set of small objects

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H I G H L OW H I G H Procedures Set of Small Objects L OW C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E Really big objects The wrong set of small objects

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PAT T E R N S https://www.flickr.com/photos/dakluza/6665460621

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O B S E R V E R N E W E M A I L User

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O B S E R V E R User UserObserver

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O B S E R V E R User UserObserver ! E M A I L N E W

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H I G H L OW H I G H L OW E A S I E R TO C H A N G E H A R D E R TO U N D E R S TA N D C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E

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https://www.flickr.com/photos/betsyweber/5902421276

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https://www.flickr.com/photos/grungetextures/4162992874

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S O L I D https://www.flickr.com/photos/chrisjfry/309574260/

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N A M E S U M M A RY U T I L I T Y S O L I D

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S I N G L E R E S P O N S I B I L I T Y P R I N C I P L E S O L I D https://www.flickr.com/photos/shenamt/8582808329/

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N A M E S U M M A RY U T I L I T Y S S I N G L E R E S P O N S I B I L I T Y O N E R E S P O N S I B I L I T Y P E R C L A S S M E D O L I D

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N A M E S U M M A RY U T I L I T Y S S I N G L E R E S P O N S I B I L I T Y O N E R E S P O N S I B I L I T Y P E R C L A S S M E D O L I D

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O P E N / C L O S E D P R I N C I P L E S O L I D https://www.flickr.com/photos/28481088@N00/4063800774/

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N A M E S U M M A RY U T I L I T Y S S I N G L E R E S P O N S I B I L I T Y O N E R E S P O N S I B I L I T Y P E R C L A S S M E D O O P E N / C L O S E D D O N ’ T E D I T C O D E ; A D D N E W C O D E L O W L I D

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L I S KOV S U B S T I T U T I O N P R I N C I P L E S O L I D https://www.flickr.com/photos/vpickering/14416940341/

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DevMynd Let Φ(x) be a property provable about objects x of type T. Then Φ(y) should be true for objects y of type S where S is a subtype of T.

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L I S KOV S U B S T I T U T I O N P R I N C I P L E S O L I D https://www.flickr.com/photos/vpickering/14416940341/

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I T ’ S N E V E R TO O L AT E TO https://www.flickr.com/photos/wcouch/8578612563/

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N A M E S U M M A RY U T I L I T Y S S I N G L E R E S P O N S I B I L I T Y O N E R E S P O N S I B I L I T Y P E R C L A S S M E D O O P E N / C L O S E D D O N ’ T E D I T C O D E ; A D D N E W C O D E L O W L L I S K O V S U B S T I T U T I O N I N H E R I TA N C E . I T ’ S A T H I N G . L O W I D

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I N T E R FA C E S E G R E G AT I O N P R I N C I P L E S O L I D https://www.flickr.com/photos/66126733@N04/8477516123/i

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W H Y S E G R E G AT E I N T E R FA C E S ? Musician AlbumCreator recordSong editSong mixSong sellMerch playSetList Gig

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W H Y S E G R E G AT E I N T E R FA C E S ? Musician AlbumCreator recordSong editSong mixSong sellMerch playSetList Gig driveVan

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W H Y S E G R E G AT E I N T E R FA C E S ? StudioActions AlbumCreator recordSong editSong mixSong sellMerch playSetList Gig driveVan VenueActions

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N A M E S U M M A RY U T I L I T Y S S I N G L E R E S P O N S I B I L I T Y O N E R E S P O N S I B I L I T Y P E R C L A S S M E D O O P E N / C L O S E D D O N ’ T E D I T C O D E ; A D D N E W C O D E L O W L L I S K O V S U B S T I T U T I O N I N H E R I TA N C E . I T ’ S A T H I N G . L O W I I N T E R FA C E S E G R E G AT I O N M A K E T H E A P I S M A L L H I G H D

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D E P E N D E N C Y I N V E R S I O N P R I N C I P L E S O L I D https://www.flickr.com/photos/hansmaulwurf/13702053625/

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N A M E S U M M A RY U T I L I T Y S S I N G L E R E S P O N S I B I L I T Y O N E R E S P O N S I B I L I T Y P E R C L A S S M E D O O P E N / C L O S E D D O N ’ T E D I T C O D E ; A D D N E W C O D E L O W L L I S K O V S U B S T I T U T I O N I N H E R I TA N C E . I T ’ S A T H I N G . L O W I I N T E R FA C E S E G R E G AT I O N M A K E T H E A P I S M A L L H I G H D D E P E N D E N C Y I N V E R S I O N M O V E C H O I C E S T O E D G E S O F S Y S T E M H I G H

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N A M E S U M M A RY U T I L I T Y S S I N G L E R E S P O N S I B I L I T Y O N E R E S P O N S I B I L I T Y P E R C L A S S M E D O O P E N / C L O S E D D O N ’ T E D I T C O D E ; A D D N E W C O D E L O W L L I S K O V S U B S T I T U T I O N I N H E R I TA N C E . I T ’ S A T H I N G . L O W I I N T E R FA C E S E G R E G AT I O N M A K E T H E A P I S M A L L H I G H D D E P E N D E N C Y I N V E R S I O N M O V E C H O I C E S T O E D G E S O F S Y S T E M H I G H

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N A M E S U M M A RY U T I L I T Y S S I N G L E R E S P O N S I B I L I T Y O N E R E S P O N S I B I L I T Y P E R C L A S S M E D O O P E N / C L O S E D D O N ’ T E D I T C O D E ; A D D N E W C O D E L O W L L I S K O V S U B S T I T U T I O N I N H E R I TA N C E . I T ’ S A T H I N G . L O W I I N T E R FA C E S E G R E G AT I O N M A K E T H E A P I S M A L L H I G H D D E P E N D E N C Y I N V E R S I O N M O V E C H O I C E S T O E D G E S O F S Y S T E M H I G H

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https://www.flickr.com/photos/29295318@N08/19322005453

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S T R AT E G Y & TA C T I C S https://www.flickr.com/photos/teegardin/6150427712/

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\ O / \ O / \ O / G OA L : P R O M O U N TA I N E E R S T R AT E G Y: C L I M B T H I S M T N TA C T I C S : T H E R O U T E U P https://www.flickr.com/photos/frenchy/222016256/

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\ O / \ O / \ O / G OA L : P R O M O U N TA I N E E R S T R AT E G Y: C L I M B T H I S M T N TA C T I C S : T H E R O U T E U P 1 2 3 https://www.flickr.com/photos/frenchy/222016256/

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G OA L : P R O M O U N TA I N E E R S T R AT E G Y: C L I M B T H I S M T N TA C T I C S : T H E R O U T E U P \ O / https://www.flickr.com/photos/frenchy/222016256/

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G OA L : P R O M O U N TA I N E E R S T R AT E G Y: C L I M B T H I S M T N https://www.flickr.com/photos/frenchy/222016256/

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G OA L : C H A N G E A B L E S O F T WA R E S T R AT E G Y: TA C T I C S : O O D E S I G N S O L I D https://www.flickr.com/photos/sunfox/5084875405/

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G OA L : C H A N G E A B L E S O F T WA R E S T R AT E G Y: TA C T I C S : O O D E S I G N S O L I D https://www.flickr.com/photos/sunfox/5084875405/

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N A M E S U M M A RY U T I L I T Y S S I N G L E R E S P O N S I B I L I T Y O N E R E S P O N S I B I L I T Y P E R C L A S S M E D O O P E N / C L O S E D D O N ’ T E D I T C O D E ; A D D N E W C O D E L O W L L I S K O V S U B S T I T U T I O N I N H E R I TA N C E . I T ’ S A T H I N G . L O W I I N T E R FA C E S E G R E G AT I O N M A K E T H E A P I S M A L L H I G H D D E P E N D E N C Y I N V E R S I O N M O V E C H O I C E S T O E D G E S O F S Y S T E M H I G H

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G OA L : C H A N G E A B L E S O F T WA R E S T R AT E G Y: TA C T I C S : S O L I D P R I N C I P L E S https://www.flickr.com/photos/sunfox/5084875405/

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G OA L : C H A N G E A B L E S O F T WA R E S T R AT E G Y: TA C T I C S : S O L I D P R I N C I P L E S https://www.flickr.com/photos/sunfox/5084875405/

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G OA L : C H A N G E A B L E S O F T WA R E S T R AT E G Y: TA C T I C S : S O L I D P R I N C I P L E S https://www.flickr.com/photos/sunfox/5084875405/

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https://www.flickr.com/photos/jonathancohen/15420956905

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H I G H L OW H I G H L OW The wrong set of small objects ❗ C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E

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DevMynd T H E O N LY WAY TO M A K E A S TO P - T H E - WO R L D R E FA C TO R I N G WO R K I S TO N OT D O I T . http://www.imdb.com/title/tt0086567/

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https://www.flickr.com/photos/frenchy/222016256/

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https://www.flickr.com/photos/frenchy/222016256/

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DevMynd post.comments.first.author.email NOPE

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DevMynd https://www.flickr.com/photos/83794824@N07/8059223873/

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S TA B L E

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S TA B L E

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S TA B L E S M E L L Y O U R C O D E https://www.flickr.com/photos/pedrosimoes7/169983321/

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T I N Y P R O B L E M S F I R S T S TA B L E https://www.flickr.com/photos/ian-arlett/13706787684/

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S TA B L E https://www.flickr.com/photos/ian-arlett/13706787684/ T I N Y P R O B L E M S F I R S T

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A U G M E N T T E S T S S TA B L E https://www.flickr.com/photos/horiavarlan/4273968004/

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https://www.flickr.com/photos/horiavarlan/4273968004/ S TA B L E A U G M E N T T E S T S

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S TA B L E BA C K U P https://www.flickr.com/photos/mjonasson/19228720295/

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S TA B L E L E AV E I T B E T T E R T H A N Y O U F O U N D I T https://www.flickr.com/photos/spierisf/6989462184/

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https://www.flickr.com/photos/spierisf/6989462184/ S TA B L E L E AV E I T B E T T E R T H A N Y O U F O U N D I T

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https://www.flickr.com/photos/spierisf/6989462184/ S TA B L E L E AV E I T B E T T E R T H A N Y O U F O U N D I T

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E X P E C T G O O D R E A S O N S S TA B L E https://www.flickr.com/photos/an_untrained_eye/5012331537

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https://www.flickr.com/photos/an_untrained_eye/5012331537 S TA B L E E X P E C T G O O D R E A S O N S

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S S M E L L Y O U R C O D E T T I N Y P R O B L E M S F I R S T A A U G M E N T T E S T S B B A C K U P L L E AV E I T B E T T E R E E X P E C T G O O D R E A S O N S

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S S M E L L Y O U R C O D E T T I N Y P R O B L E M S F I R S T A A U G M E N T T E S T S B B A C K U P L L E AV E I T B E T T E R E E X P E C T G O O D R E A S O N S

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DevMynd https://twitter.com/kentbeck/status/250733358307500032

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DevMynd https://twitter.com/kentbeck/status/250733358307500032

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https://www.flickr.com/photos/frenchy/222016256/

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\ O / https://www.flickr.com/photos/frenchy/222016256/

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https://www.flickr.com/photos/bevrichardmartin/5985876061/ https://www.flickr.com/photos/discarnate/27211024/ https://www.flickr.com/photos/lynardie/16191183291/

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DevMynd Sarah Mei sarah@devmynd.com @sarahmei THANK YOU!