A presentation on layered software architecture that goes through logical layering and physical layering, the difference between those two and a practical example.

1. Layered Architecture
Lars-Erik Kindblad
Senior Consultant
Blog: kindblad.com

2. Agenda
 Logical Layer Architecture
 Example Code
 Physical Tier Architecture
 Logical Layer vs Physical Tier Architecture
 Summary
 Questions
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3. LOGICAL LAYER ARCHITECTURE
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4. 3-Layer Architecture
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5. Presentation Layer
 Also known as Frontend Layer, User Interface (UI) Layer
 Responsible for creating and displaying the user interface and
handling user interaction
 Data shown is fetched from the Domain Layer
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6. Service Layer
 Also known as Web Service Layer
 Responsible for exposing a web service API and returning the
method result as XML or JSON
 Data returned is retrieved from the Domain Layer
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7. Domain Layer
 Also known as Business Layer
 Responsible for all the business logic in the application
 Consists of a Domain Model and Domain Services
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8. Domain Model
 Also known as Business Model, Business Objects, Entities etc.
 Responsible for having a model that reflects how the business
stakeholders look at the world
 Consists of entities with relationships and behavior
 Similar to a database model but a domain model is richer
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9. Domain Service
 Also known as Business Services, Business Managers etc.
 Business logic that does not belong within an entity
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10. Infrastructure Layer
 Also known as Data Access Layer, Repository Layer etc.
 Responsible for querying a database, calling a web service, sending
e-mail etc.
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11. Example
 We want to create a banking application with customers and related
accounts. An account consist of an account number, a balance and
a credit limit.
If the account has been overdrawn then the account and customer is
considered to be “sick”, otherwise “healthy”
 Use Case 1: As a user I want to see if a customer is healthy or sick
 Use Case 2: As a user I want to retrieve if a customer is healthy or
sick through a web service
 Technology: .NET, ASP.NET MVC, WCF
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12. What do we need?
1. Domain Model for Customer and Account
2. Business logic for deciding if an account and customer is healthy or
sick
3. 2 Classes: Fetching Customer and fetch list of Accounts from the
database
4. Service Class for building up a Customer Entity with Accounts
Use Case 1:
1. MVC Controller and a View to display the health status for a given
customer
Use Case 2:
1. WCF Service for returning whether a customer is healthy or not
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13. Domain Model
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14. Domain Model
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15. Progress
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16. Infrastructure – Fetch Customer
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17. Infrastructure – Fetch Accounts
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18. Progress
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19. Domain Service – Build a Complete Customer
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20. Progress
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21. Use Case 1: Show the result to the user
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22. Progress
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23. Use Case 2: Return the result through a Web Service
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24. Completed
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25. Visual Studio Project Structure
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26. Why should you have many layers?
 Less code per layer
 Reduced complexity
 Easier to maintain code
 Easier to add new functionality
 Easier to test
 Allows for reuse code across the application
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27. PHYSICAL TIER ARCHITECTURE
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28. Logical Layer vs Physical Tier
 A Logically Layer is how you logically divide the code in the
application
 A Physical Tier is how you divide your application into multiple sub-
applications that can run on separate servers
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29. 2-Tier Windows Client Architecture
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30. 3-Tier Windows Client Architecture
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31. 3-Tier Web Architecture
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32. 4-Tier Architecture
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33. Why have many tiers?
 Reuse logic across applications
 Improve security, e.g. restrict database access for the client by going
through a service
 Improved performance, the performance critical tiers can be scaled
across multiple servers
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34. Summary
 Logical Layers
• How you logically divide the code in the application
• Three Layer Architecture is most common
o Presentation Layer or Service Layer
o Domain Layer with a Domain Model and Domain Services
o Infrastructure layer for communicating with data sources
 Physical Tiers
• How you divide the application into many sub-applications
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35. QUESTIONS?
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36. www.capgemini.com
The information contained in this presentation is proprietary. ©2010 Capgemini. All rights reserved