This document provides a summary and conclusions from a lecture on enterprise application architecture. It discusses that building complex computer systems gets exponentially harder with increased complexity. However, with proper techniques like layering, interfaces, object-oriented programming, design patterns, and frameworks, building large multi-tier systems can be done incrementally. It emphasizes separating concerns, minimizing dependencies between layers, and avoiding unnecessary complexity. Practical considerations include avoiding overdesign, overconfiguration, and not being constrained by frameworks. The future of enterprise software will involve challenges of connectivity between an increasing number of devices and software integration through APIs, cloud computing, and mobility.

1. Lecture 14
Summary and Conclusions

2. “Advice is a dangerous gift”
There are no right answers
Use the advice to prod your
thinking, but don’t use it as a
replacement for your thinking
And remember, architecture is not
cast in stone

3. Building Enterprise Applications
 Building computer systems is hard
– As the complexity of the
system gets greater, the
task of building the
software gets
exponentially harder

4. Building Enterprise Applications
 Building computer systems is hard
Software
Architecture
Design
Pattern
OO
Programming
Middleware
Frameworks

5. Building Enterprise Applications
 Building computer systems is hard
 But now when we know how to, it’s not that hard
anymore

6. Goals of an Enterprise Architecture






Be robust
Be performing and scalable
Take advantage of OO design principles
Avoid unnecessary complexity
Be maintainable and extensible
Be easy to test

7. Enterprise Systems
 Building large multi-tier systems is done one line
at a time
–
–
–
–
–
–
–
–
Layering
Clear interfaces
Minimize dependencies
Separation of concerns
Object Oriented programming
Design patterns
Frameworks
Testable code

8. Create Abstractions
 Minimize dependence on subsystems
– Must be easy to change
• Gateway, Mapper, Service Stub
 Abstract things that varies from what stays the
same
– Design principles
• Factory, Plugin, Dependency Injections

9. Separation of Concerns
One of the main challenge of frameworks is to
provide separation of concerns
Frameworks deal with generic functionality
Frameworks need patterns to combine generic and
domain specific functionality

10. Minimize dependencies
 Be careful with dependencies
– It is easy to create code where modules depend on
other modules
• Plugin, Factory, Service Layer, Separated Interface,
Dependency Injection and Observer Pattern

11. Layering
 Software systems can get complicated
– Abstractions are needed
 Provides abstraction by separating computer
systems in layers
– Higher layers use services from
lower layers
– Each layer has dedicated task
and hides complexity from upper
layers

12. The Three Layers
 Presentation
– User’s interface to the system
– User can be another system
– Accepts input, displays views
 Domain
– The Application of the system
– The “Business logic”
– Has the tendency to creep into other layers
 Data Source
– Connection to the database

13. Three Layers
 Presentation Layer for the User Interface
 Domain Layer for the domain logic
 Persistence Layer for the data access

14. Considerations
 Don’t overdesign!
– User Interfaces are really difficult to make generic and
reusable
– If there is no need for extra layer, don’t have it
– If you don’t need an interface, don’t have it
 Don’t let frameworks rule you!
– If you have to write code just to satisfy a framework,
maybe there is another way – or fix the framework
– Frameworks can overdo it

15. Considerations
 Don’t overdo Configurations
– Sometimes coding is better than config
– Testing and debugging config is hard
 Don’t be afraid to Refactor
– You can always add another indirection
– You can always add a new layer
 Design Principles are good guidelines
– Don’t be afraid to reevaluate them

16. Practical Considerations
 Risk is in feature creep and things out of control

17. Practical Considerations
 Solutions are designed and implemented
according to time schedule and budget
– Hardest part is management of people

18. Practical Considerations
 Agile is an answer to this
Daily
Standup
Sprint
stories
Backlog
Backlog
ordered by
Product Owner
Working
Product
1-2 week
sprints
Working
Product
Released

20. Future of Enterprise Software

21. THE DIGITAL DECADE
TV SHOWS
MOVIES
MUSIC
VOICE
PICTURE
S
SMARTPHONES
BOOKS
2000
2010

22. DIVERGE
Smartphones
Personal Computers
Wearable
Laptops
Tablets
Mini computers
Internet of things
2G Cell phones
Music player
Smart TV
Mainframes
Servers
Clusters
SaaS - APIs
Cloud – utility computing
CONVERGE
1960
1970
1980
1990
2000
2010

23. Wearable Era

24. Digital Online World
Work
More
information
Focused
Consuming
Video
Information
Browsing
Consuming
content
Checking
Mobile
Now
Real-time

25. VIDEO
BEFORE
Video stores, late
fees, clutter of DVDs
NOW
Any (almost) movie available
anytime anywhere
25

26. COMPUTERS
BEFORE
NOW
Desktops, clunky laptops
Mobile, light, easy to carry
26

27. INTERFACE
BEFORE
NOW
Keyboard, mouse
Touch, voice, gesture
27

28. BOOKS
BEFORE
NOW
Printed books, libraries,
clutter of books
Digital, online library,
audiobooks

29. MAGAZINES
BEFORE
Printed, clutter
NOW
Digital, automatically
delivered

30. MAPS
BEFORE
NOW
Printed, maps, static
and outdated
Real-time, satnav, with
directions, info

31. COOKBOOKS
BEFORE
Books with fixed units
NOW
Interactive, with variable
units, video demos

32. OWNERLESS LIFESTYLE
BEFORE
NOW
Own stuff, cluttered
home
Online
stuff, renting, freedom

33. The Post-PC Era
 The Personal Computer era is over
– Rise of the network
– APIs
– Enterprise systems are accessible
by consumers
– New devices, mobile phone,
ITV, game machines, MP3 players,...
Source: (cc) 1998-2008
Digibarn Computer Museum,
Source: Picture from Convergence Transforms Digital Home: Techno-Economic
Impact

34. Challenges in Computing
Hardware
1980
Connecting hardware
Network
1990
Software
Connecting
software
2000
 Software and integration of components and
devices are the challenges ahead
 Cloud computing and ubiquity
 Move to Service Oriented Architecture and APIs

35. Challenges in Computing
Software
2000




Connecting
software
2010
Mobility
Wearables
APIs, SaaS, real-time
2020
Multiple devices – anything can connect
Ability to predict – know the users
Data Analytics aka Big Data
Real-time streams

37. Objectives
 Know the basics of software design and
beautiful code
 Understand and know how to use design
patterns
 Implement software framework with component
reuse in mind

38. Objectives continued
 Understand different software architectures and
the different design choices
 Understand Software Oriented Architecture
(SOA) and Software as a Service (SaaS)
 Understand the practices of how professional
software is developed in the software industry

39. Lectures
L01 Enterprise Application Architecture
Introduction, 1
L02 Software Design
L03 Design Patterns Introduction
L04 Base Patterns 18
L05 Frameworks
L06 Process Design
L07 Organizing the Domain Layer 2, 9

40. Lectures
L08 Mapping to Relational Databases 3, 10
L09 Behavioral Design 3, 11
L10 Web Presentation 4, 14
L11 Application Architecture 8
L12 Concurrent Programming 5, 16
L13 Session State and Distribution Strategies 6, 7,
15, 16
L14 Summary and Conclusions

41. Thank You!
- Ólafur Andri

42. NEW TECHNOLOGY 2014, starts in January
2013 Course Description Trailer
http://www.youtube.com/watch?v=L0p9xU_XIdY