How to develop high quality software? What are the key/fundamental principles for software design? What is the relationship between principles, bad smells, design patterns, and refactoring? This presentation answers all this and more. Don't miss it!

1. How to apply design
principles in practice?
Ganesh Samarthyam!
Consultant, ZineMind LLC!
ganesh.samarthyam@zinemind.com

2. “Applying design principles is the key to creating
high-quality software!”
Architectural principles: !
Axis, symmetry, rhythm, datum, hierarchy, transformation

3. Technology changes fast => FOMO

4. Often frustrating to develop quality software!

5. There must be a better way!
“Here is Edward Bear,
coming downstairs now,
bump, bump, bump,
on the back of his head,
behind Christopher Robin.
It is, as far as ...
!
It is, as far as he knows,
the only way of coming downstairs,
but sometimes he feels that there
really is another way,
if only he could stop bumping for a
moment and think of it!”
!
- A.A. Milne

6. Think, think, think!

7. Focus on software design is the key!

8. Real scenario #1
Initial design

9. Real scenario #1
❖ How will you refactor such
that:!
❖ A specific DES, AES, TDES,
… can be “plugged” at
runtime?!
❖ Reuse these algorithms in
new contexts? !
❖ Easily add support for new
algorithms in Encryption? !
Next change:
smelly design

10. Time to refactor!
Three strikes and you
refactor
Martin Fowler

11. Potential solution #1?
Broken
hierarchy!
Yuck! !
Your solution smells

12. Potential solution #2?
Algorithms not
reusable!
Hmm, can be better. !
Better luck next time…

13. Potential solution #3?
Wow!!
What a nice solution :)

14. Can you identify the pattern?

15. You’re right: Its Strategy pattern!

16. Real scenario #2
Initial design

17. Real scenario #2
How to add support for new
content types and/or algorithms?
Yuck! !
This design smells

18. How about this solution?
Wow!!
What a nice solution :)

19. Can you identify the pattern structure?

20. You’re right: Its Bridge pattern!

21. Wait, what principle did we apply?

22. Open Closed Principle (OCP)
Software entities should be open for
extension, but closed for modification
Bertrand Meyer

23. Variation Encapsulation Principle (VEP)
Encapsulate the concept that varies
Erich Gamma, Richard Helm, Ralph Johnson and John Vlissides

24. Fundamental principle: Encapsulation
The principle of encapsulation advocates separation of concerns and!
information hiding through techniques such as hiding implementation!
details of abstractions and hiding variations

25. Enabling techniques for encapsulation

26. Other fundamental principles?
Principles*
Abstrac/on*
Encapsula/on*
Modulariza/on*
Hierarchy*

27. Applying principles in practice
Encapsulation
Violating!
encapsulation
Adherence to !
encapsulation
Applying !
encapsulation

28. Applying principles in practice
Principle
Violating!
principles
Adherence to !
principles
Refactoring
Bad design !
(with smells)
Good design
(with patterns)

29. Design determines qualities
DESIGN
impacts
impacts
impacts
Understandability Changeability Extensibility
Reusability Testability Reliability

30. “Applying design principles is the key to creating
high-quality software!”
Architectural principles: !
Axis, symmetry, rhythm, datum, hierarchy, transformation

31. Presentation source
Forewords by
Grady Booch and Dr.
Stephane Ducasse

32. What are your takeaways?

33. Image/video credits
❖ http://en.wikipedia.org/wiki/Fear_of_missing_out!
❖ http://lesliejanemoran.blogspot.in/2010_05_01_archive.html!
❖ http://javra.eu/wp-content/uploads/2013/07/angry_laptop2.jpg!
❖ https://www.youtube.com/watch?v=5R8XHrfJkeg!
❖ http://womenworld.org/image/052013/31/113745161.jpg!
❖ http://www.fantom-xp.com/wallpapers/33/I'm_not_sure.jpg!
❖ https://www.flickr.com/photos/31457017@N00/453784086 !
❖ https://www.gradtouch.com/uploads/images/question3.jpg!
❖ http://gurujohn.files.wordpress.com/2008/06/bookcover0001.jpg !
❖ http://upload.wikimedia.org/wikipedia/commons/d/d5/Martin_Fowler_-_Swipe_Conference_2012.jpg!
❖ http://www.codeproject.com/KB/architecture/csdespat_2/dpcs_br.gif !
❖ http://upload.wikimedia.org/wikipedia/commons/thumb/2/28/Bertrand_Meyer_IMG_2481.jpg/440px-
Bertrand_Meyer_IMG_2481.jpg !
❖ http://takeji-soft.up.n.seesaa.net/takeji-soft/image/GOF-OOPLSA-94-Color-75.jpg?d=a0 !
❖ https://developer.apple.com/library/ios/documentation/cocoa/Conceptual/OOP_ObjC/Art/watchcalls_35.gif!
❖ http://www.pluspack.com/files/billeder/Newsletter/25/takeaway_bag.png !
❖ http://cdn1.tnwcdn.com/wp-content/blogs.dir/1/files/2013/03/design.jpg