The document discusses layered architecture in application development, focusing on the logical and physical layers. It describes key components such as the presentation layer, service layer, domain layer, and infrastructure layer, along with their responsibilities. The document also emphasizes the benefits of using multiple layers and tiers for better maintainability, scalability, and security.

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