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