1. SOEN 343 Software Design
Computer Science and Software Engineering Department
Concordia University
Fall 2004
Instructor: Patrice Chalin

2. Agenda – Lecture 5b Review & renew. How do I come up with a design?
Introduction to Architectural Styles
Client-server
Layered
Servlets, an introduction.
Exercise Set 4
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SOEN 343, © P.Chalin,

3. Opening Remarks Tutorial period: Homework
Tutorial 5: Short. Java Servlets, A First Contact.
Nothing to submit this time.
Take the time to finish other tutorials (and ask tutors for help if needed).
(Ask questions about Quiz 1 if you require further clarifications.)
Homework
Hand it in before the end of the class.
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SOEN 343, © P.Chalin,

4. [Design, How To?]-----------------

5. How Do I Come Up With a Design?
Given
Product requirements.
Project plan
How do I come up with a design?
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SOEN 343, © P.Chalin,

6. Design – Repeat Successes
Has a (successful) similar product been built?
Yes, then reuse domain specific:
Architectural
Style (e.g. client/server, database, process control)
Patterns.
Design Patterns (& idioms).
Use Domain model as source of inspiration.
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SOEN 343, © P.Chalin,

7. Design – New Application Area?
Has a (successful) similar product been built?
No, then choose among general:
Architectural
Style (e.g. client/server, database, process control)
Patterns.
Design Patterns (& idioms).
Use Domain model as source of inspiration.
This course: offering guidelines, suggesting choices.
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SOEN 343, © P.Chalin,

8. Common Architectural Styles [FYI]
Dataflow
Pipes and filters
Batch sequential
Data-centered
Repository
Blackboard
Virtual Machine
Interpreter
Rule-based system
Call and Return
Main program and subroutine
Object-oriented (& Data abs.)
Layered
Independent Components
Communicating processes
Client/server
Event systems
Implicit invocation
Explicit invocation
[BCK98, Fig 5.1 p. 95]
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9. Layered Architectural Style
Our focus today:
Architectural style: Layered.
References
Larman, Chapter 30 (Section 30.2).
Fowler, EA.
Briefly, lets review Client-Server
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10. Client-Server (Two-tiered System)
“… most people see tier as implying a physical separation. Client-server systems are often described as two-tier systems …” [Fowler, p.19]
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11. Enterprise Application Layers
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12. Enterprise Application Layers
Presentation
Domain Logic
Data Source
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13. Layering – General Scheme
Layers
Presentation / Application.
UI.
Generally “thin”.
(Term “application” can be misleading. It does not mean …)
Domain / Business Logic.
Core system functionality.
Technical Services.
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14. Domain Logic (Layer)
“… also referred to as business logic. … It involves calculations based on inputs and stored data, validation of any data that comes in from the presentation, and figuring out exactly what data source logic to dispatch …” [Fowler, p.20]
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15. Layered Style Characteristics
Each layer offers services to layers above.
Hence, layers build upon each other to provide increased functionality.
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16. Layers: Functionality
Presentation
Domain
Functionality / services
Data Source
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17. Presentation Domain Data Source Layers: Dependencies Dependencies
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18. Layer Dependencies Example
Larman Fig. 30.4
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19. Not permitted in pure style
Layering – Pure Style
Pure style: components are permitted to use services of other components in
same layer.
layer immediately below.
Not permitted in pure style
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20. Where to Run Your Layers
[Folwer, pp ]
Your software application ? ?
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21. Where to Run Your Layers
EA software
Technical Services
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22. Presentation Domain Logic Data Source EA Layers Refined
Refine by splitting each layer into two.
Data Source
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23. General Layering Scheme Refined
Presentation
Domain
Technical services
Presentation
Application
Domain (logic)
Low-level domain logic
Technical services
Foundation.
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SOEN 343, © P.Chalin,

24. General Layering Scheme Refined
Presentation
Domain
Technical services
Presentation
Application
Business services
Low-level business services
Technical services
Low-level technical services
Alternate names for
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25. Layering (Larman) See Larman Sect 30.2 for examples of layer content.
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26. Servlets, The General Idea
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27. Exercise Set 4
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SOEN 343, © P.Chalin,