This document introduces patterns and discusses how they are not unique to computer science, but have existed for thousands of years. It provides examples of earliest patterns like astronomical constellations and periodic tables. It then explains how object-oriented design patterns like singleton, factory and builder appear in nature, giving examples like traffic police, brand stores, and construction. Finally, it discusses how many other software design patterns like proxy, facade, and mediator can be seen in examples from daily life and literature.

1. Prakash Sathiyamoorthy

2. Presentation Overview
 Introduction to Patterns
 Patterns are not only for C.Sc.
 Earliest Patterns.
 Patterns in C.Sc. To real life.

3. Patterns - What are they?
 Natural human thought process
 Helps to solve problems effectively
 Easy to recognize
 Has been in use for thousands of years
 We come across them everyday

4. Patterns - Not a C.Sc Subject
 Computer Science has adopted a version of Design
Patterns.
 Design patterns are for everyone.

5. Earliest Patterns - 1
 Astronomical constellations

6. Earliest Patterns - 2
 Rangolis

7. If only C.Sc used Patterns 
Shortest path
connecting the dots !

8. Earliest Patterns - 3
 Periodic table of elements

9. Patterns in Nature - OOPS
 OOPS –
 Separation of responsibilities.
 Nothing much 

10. Example - OOPS
Imagine if you are a single person :
building your own house,
manufacturing your own car,
cooking your own food,
farming your own crops,
stitching your own dresses,
doing laundry,
running your own transport,
making your own televisions,
running your own channels, etc. etc. etc….

11. OOPS !!! (literally) missed
making your own software !

12. Patterns in Nature - Singleton
 Problem: Controlling traffic in a road junction.
Imagine having a police for every direction.
 Solution: Place one at the center.
 Example: Traffic police in junctions.
Pic follows

14. Patterns in Nature - Factory
 Problem: Imagine visiting every brand’s showroom
separately i.e. Reebok, Peter England, etc.
 Solution: Keep every brand under one roof so it is
easy to find everything in the same place.
 Example: Brand factory

15. Patterns in Nature - Builder
 Problem: A guy that’s wants to own a house most of
the times cannot build himself/herself.
 Solution: Handover the responsibility of building the
house to a builder who specializes in that.
 Example: Construction builder

16. Patterns in Nature - Prototype
 Problem: Imagine writing lecture notes laboriously
during the lecture in college.
 Solution (Easy) : Take photocopies from the front row
guys 
 Example: Xerox copies

17. Patterns in Nature - Pool
 Problem: Everyone wants to pick up the same book the
subject lecturer announces. You cannot have infinite copies
of a title. Even if you do, not all would be required.
 Solution: Have finite set of copies and keep circulating
that.
 Examples:
 Lending books from library
 Cabs servicing customers

18. Patterns in Nature - Flyweight
 Problem: Making ice for every color is not only costly
but also unnecessary.
 Solution: Have ice separately so it is easy to mix the
essence which differs among orders.
 Example: ice gola (Pic follows)

20. Patterns in Nature - Composite
 Some patterns are hard to explain and this is one of
them, so lets skip 

21. Patterns in Nature - Adapter
 Problem: You reach US and try to connect your
Laptop you purchased in India and end up in trouble.
 Solution: You get a India-US plug adapter that can
connect your plug to the wall socket.

22. Patterns in Nature - Decorator
 Problem: Well, there are no problems here actually.
 Solution: A solution is not required when there is no
problem  So a decorator just adds up to the beauty of
the original. May be having undecorated could be
scary 
 Example: suspense here, next slide

23. And he is the
“Decorator”

24. Patterns in Nature - Proxy
 Problem: Original may be presented later until
absolutely required.
 Solution: Place a substitute for time being.
 Example:
 Proxy attendance, reserving bus seat with kerchief
(could be any piece of cloth actually )
Bus seat reservation with kerchief

25. Patterns in Nature - Bridge
 Remember, some patterns cannot be explained so
easily? This is the second one, so we’ll skip.

26. Patterns in Nature - Facade
 Problem: Hide the complexity and expose a much
simpler and a easy to understand look.
 Solution: Cover the complex portion with a thing that
looks simpler and beautiful.
 Example: A modern building’s façade
Pic follows

28. Patterns in Nature - COR
 Problem: One person/entity is burdened with all the
responsibilities.
 Solution: Delegate the individual responsibilities so that
one person/entity is not burdened with all the work.
 Examples:
 A typical hotel scenario – biller -> Server -> Cook
 A government office – extended COR 

29. Patterns in Nature - Template
 Problem: Making commonly used patterns is time consuming
 Solution: Avoid commonly used but time consuming work by
having a ready made shape that can be used as a reference to
make the intended one easily
 Examples:
 Stencils in school
 Painting templates
Do you realize how early you
started applying design patterns?

30. Patterns in Nature - Interpreter
 Problem: Need a dedicated way of handling a small
domain related work.
 Solution: Define a domain specific language, the
grammar, rules for interpretation, etc.
 Example: Language used in avatar (Na'vi) : Define a
domain’s own language and the interpretation rules.

31. Patterns in Nature - Command
 Problem: Need a command in between that will
shorten things up. Imagine every customer of hotel
talking to the cook directly !
 Solution: Have a person/thing in between who can
take the command and delegate the request and
handle it back.
 Example: A server in hotel – One who takes the
request is not the one that does the actual work.

32. Patterns in Nature - Iterator
 Problem: Need a easy way to visit every member of a
group.
 Solution: Have a representation of the collection so it
is easy to callout each person.
 Example: An attendance register.

33. Patterns in Nature - Mediator
 Problem: Need to mediate things so that the
individual entities can have easy and effective
communication.
 Solution: Place a mediator who will mediate between
the things. In our example, quikrr or ebay mediates
between buyers and sellers.
 Example: Quikrrrrrrrrrrr, ebay

34. Patterns in Nature - Memento
 Problem: Need to keep a memory for every occasion
so it is easy to recollect later.
 Solution: Have a memento for every occasion.
 Example: from Ramayana, next slide.

35. Aaranya Kand
1. Sita asks Rama to fetch the deer for her
2. Maricha (the daemon) shouts in the voice of
Rama asking for Lakshmana for help.

36. 3. Lakshman draws the restricted boundary line
for Sita.
4.Ravana makes Sita to cross the line so that he can
abduct her.
5. Ravana succeeds in abducting Sita

37. Sita is in deep trouble
Now comes the “Memento” design pattern to Sita’s
rescue.
6. Sita keeps throwing her
ornaments (mementos) for
Rama to trace the route to find
her !
No computer program would have applied this pattern before Sita did 

38. Conclusion
•So, Design Patterns are definitely not invented for
Computer Science !
•We see, hear, experience and come across many patterns
in our daily life.
•Gang-Of-Four patterns are not the complete list of
patterns.

39. Thank You !
Prakash.sathiyamoorthy@gmail.com