How do you write objects for cloud computing? Is Object Oriented Programming still THE way to write apps? What about the state that objects contains?

1. Objects in the Cloud
Edizione 2014
Marco Parenzan

2. Objective
Thinking about #state, #objects and how #cloud
need respect using #state and writing #objects

3. Musing about some modern
#misconceptions

4. We cannot take it for granted that…
 The network is reliable
 Latency is negligible
 bandwidth is infinite
 the net is safe
 the topology doesn't change
 The transport cost is negligible/zero
 the network is homogeneous
 there is only one administrator
Mauro Servienti - http://www.communitydays.it/events/2014/vs06/

5. Objects in the Cloud
Can we apply traditional object oriented
principles to the #cloud?
Can we think #state as just #objects value?

6. Why thinking about #state?
#state does not fits so well in the #cloud with:
#network
#scaling
#mainteinance
#performances

7. What is #state here?

8. Understanding
#state and #behavior

9. What is state?
Is a set of attributes (of something) that allows you
to identify and characterize it
State is something that is maintained in absence of
inputs

10. State and #software
Every software program have a #state
That state is what we want for the program
In #traditional software development we don’t
focus on #state, it’s just there
We focus on behavior and how to express it

11. What is a behavior?
 It’s something you can do on a state to change it
 Everything you do is to change yourself (at least!)
 Many ways to express behavior
 Imperative
 “Run that behavior on that state”!
 Functional
 It’s a relationship between values
 It’s a relationship between state (of something) in two different times (before
and after)

12. Why state and behavior are important?
Because statet+1=behaviorj(inputt, st)
Where t and t+1 are two consecutive instants
And there are cases where statet+1=statet

13. Where is state?
 In memory
 Variables
 In transient storages (timeout): faster more than infinite
 Caches
 Sessions
 In persistent storage (tinfinite - MTBF)
 Blobs
 In structured data
 Files
 Databases

14. Choose the right representation
Choosing the right representation of the state is
the most difficult part of an application
Relational Database is a choose, not a starting point

15. State and the Cloud
In the #cloud, the state is the most important thing
Define the correct state and how to represent it

16. Just objects

17. What is an object?
It is state and behavior in the same “place”

18. What is an attribute?
Is a characteristic (of an object) you can measure
(it has a value)

19. Some quotes
Everything is an object…
…so everything have a state
…so everything have a behavior
If an object have no behavior, is still an object? Or is
just state?
If an object have no state, but only behavior, is still an
object?

20. What is modeling?
Is the activity of shaping objects

21. What is an entity
Is something you can model

22. You as programmer…
…model entities into objects

23. What is OOP (Object Oriented
Programming)?
It’s a way of modeling everything as an object,
with state and behavior
…and classes?

24. Objects, non classes
We can speak about objects without referring to
classes, ever!

25. What is a class?
A #class is a model for objects
A #class is a way to define a model for objects
A #class is the typical way to define objects models in
a strongly typed (not yet statically typed) language
(C#, Java, but also Python and Ruby)
There are other ways

26. Does a class-based language imply
OOP?
No, OOP is a way of thinking and modeling at first
Class-based languages cannot be an excuse to
avoid real principles

27. What is a prototype
Is an object itself you can use as a model to
create others objects copying from it
#javascript teaches us that we can write #objects
without #classes

28. Objects in the Cloud
Edizione 2014
Marco Parenzan