1. Software Architecture
RiSE’s Seminars
Clements’s book :: Chapters 1 and 2
Frederico Durão
April 28, 2019

2. Summary What is Software Architecture (Chapter 1)
Importance
Architecture Views
Evaluating a Software Architecture (Chapter 2)
Reasons
Software Architecture Methods
Benefits of Evaluating Software Architecture
April 28, 2019

3. What is a Software Architecture?
April 28, 2019

4. What is a SW Architecture ? :: Chapter 1
From 1990 the term Software Architecture has gained widespread acceptance when this field attracted attention from both industry and the research community
1990s
1960s
April 28, 2019

5. What is a SW Architecture ? :: Chapter 1
Importance
It is a vehicle for communication among stakeholders
It is the manifestation of the earliest design decisions
It is the reusable, transferable abstraction of a system
The software architecture of a program is the structure of the system, which comprise software components (the externally visible properties of those components) and the relationships among them.
[Bass 98]
April 28, 2019

6. What is a SW Architecture ? :: Chapter 1
1.1 Architecture as vehicle for communication among stakeholders
1.1.1 Architecture and Its Effects on Stakeholders
User wants a system usable and reliable
Costumer wants a system implemented on scheduled and to budget
Developers have to answer those through coding
1.1.2 Architectural Views
April 28, 2019

7. What is a SW Architecture ? :: Chapter 1
Architecture Views
Functional View
System functions
Data flow
Concurrency View
Set of process and threads
Performance, availability and deployment
Code View
Classes, packages, modules, libraries
UML – ex: Class Diagram
Development View
Files and Directories
CVS
Physical View
Hardware Resources
Ex: LAN Network Map, sensors, circuits, storage devices
April 28, 2019

8. What is a SW Architecture ? :: Chapter 1
1.1 Architecture as vehicle for communication among stakeholders
1.1.3 Architecture Description Languages
ADL
Success in:
Deadlock, detection, consistency, real-time
Failure in:
None of these languages has been widely adopted
UML – Success Case
April 28, 2019

9. 1.2 Architecture as the Manifestation of the Earliest Design Decisions
What is a SW Architecture ? :: Chapter 1
1.2 Architecture as the Manifestation of the Earliest Design Decisions
Decisions affects quality attributes:
Performance
Security
Modifiability
Reliability
Decisions affects the organization
Teams, Information flows
Organization process, Training
Commercial Decisions
Microsoft or Java Components?
April 28, 2019

10. 1.2 Architecture as the Manifestation of the Earliest Design Decisions
What is a SW Architecture ? :: Chapter 1
1.2 Architecture as the Manifestation of the Earliest Design Decisions
1.2.1 Architectural Styles
The earliest of the early design decisions
A set of components types
A set of connector types/interaction mechanisms
A topological layout of these components
A set of constraints on topologies and behavior
An informal description of the costs and benefits of the style
April 28, 2019

11. 1.3 Architecture as a Reusable, Transferable Abstraction of a System
What is a SW Architecture ? :: Chapter 1
1.3 Architecture as a Reusable, Transferable Abstraction of a System
Architecture is a reusable model that can become the basis for an entire family of systems…
Software Product Line
Architectural Challenges in SPL:
Which of these are the core assets?
How add new functionalities in the core assets?
April 28, 2019

12. Evaluating a Software Architecture
April 28, 2019

13. Evaluating a SW Architecture :: Chapter 2
How can we be sure whether the architecture chosen for an software is the right one?
April 28, 2019

14. Software Architecture Methods
Evaluating a SW Architecture :: Chapter 2
Software Architecture Methods
ATAM: Architecture Tradeoff Analysis Method
SAAM: Software Architecture Analysis Method
ARID: Active Reviews for Intermediate Designs
April 28, 2019

15. Why Evaluate an Architecture?
Evaluating a SW Architecture :: Chapter 2
Why Evaluate an Architecture?
The earlier an error is found, the cheaper is the cost to fix it;
Symptoms of unsuitable architecture:
No performance goals met;
No Security goals met;
Customer impatient;
Right functionality not available;
Difficulty in changes;
Schedules and budgets blown out of water;
Architecture evaluation is a cheap way to avoid disasters...
April 28, 2019

16. When Can Architecture Be Evaluated?
Evaluating a SW Architecture :: Chapter 2
When Can Architecture Be Evaluated?
The earlier an error is found, the cheaper is the cost to fix it
Symptoms of unsuitable architecture:
No performance goals met
No Security goals met
Customer impatient
Right functionality not available
Difficulty in changes
Schedules and budgets blown out of water
Architecture evaluation is a cheaper way to avoid disaster
April 28, 2019

17. Evaluating a SW Architecture :: Chapter 2
Who's Involved?
Evaluation Team
People who will perform the analysis
Stakeholders
Not all of the stakeholders will be member of the development team
The Decision Maker – ex: architect and project management
The clients are interested in the output of the evaluation
April 28, 2019

18. What Result Does an Architecture Evaluation Produce?
Evaluating a SW Architecture :: Chapter 2
What Result Does an Architecture Evaluation Produce?
Report
Answers to
Is this the architecture suitable to the needs? or
Which of two or more competing architectures is the most suitable on for the system at hand?
A suitable Architecture is reached if...
The system result meets its quality goals
The system can be built within of the budget and deadline estimated
April 28, 2019

19. For what Qualities Can We Evaluate an Architecture?
Evaluating a SW Architecture :: Chapter 2
For what Qualities Can We Evaluate an Architecture?
Performance - latency time
Reliability – system operating over the time
Availability – system is up and running
Security – resistance to attacks
Modifiability - changes
Portability – run under different environments
Functionality – do the work that is expected
Variability - reuse
Subsetability – deliver a part of product
Conceptual integrity
April 28, 2019

20. For what Qualities Can We Evaluate an Architecture?
Evaluating a SW Architecture :: Chapter 2
For what Qualities Can We Evaluate an Architecture?
Architectural Evaluation will tell us that the architecture has been found suitable with respect to one set of goals and problematic with another set of goals
The decision in which steps give is responsibility of the manager
April 28, 2019

21. Why Are Quality Attributes Too Vague for Analysis?
Evaluating a SW Architecture :: Chapter 2
Why Are Quality Attributes Too Vague for Analysis?
“The system shall exhibit acceptable performance”
...and...
“The system will perform the search in maximum 5 seconds”
What about the scenario?
“The system will perform the search in maximum 5 seconds in a Linux Platform with Oracle Database where the server is a Pentium IV HT 2.0Ghz and 1Gb RAM”
April 28, 2019

22. What are the Outputs of an Architecture Evaluation?
Evaluating a SW Architecture :: Chapter 2
What are the Outputs of an Architecture Evaluation?
Outputs from the ATAM, SAAM, and ARID
Prioritized Statement of Quality Attribute Requirements
Mapping of Approaches to Quality Attributes
Risks and Nonrisks
Outputs only from the ATAM
Catalog of Architectural Approaches Used
Approach-and- Quality-Attribute-Specific Analysis Question
April 28, 2019

23. Communication is the base of the success
Evaluating a SW Architecture :: Chapter 2
What are the Benefits and Costs of Performing an Architecture Evaluation?
Put Stakeholders in the Same Room
The first meeting of stakeholders
Forces an Articulation of Specific Quality Data
Results in the Prioritization of Conflicting Goal
Forces a Clear Explication of the Architecture
Improves the Quality of Architectural Documentation
Uncovers Opportunities for Cross-Project Reuse
It spots components that can be reused
Results in Improved Architecture Practices
Communication is the base of the success
April 28, 2019

24. Evaluating a SW Architecture :: Chapter 2
The simple and eficient things are more welcome than the complex and huge challenges
April 28, 2019

25. References CLEMENTS, P. Software Product Line. Springer-Verlag, 2005.
April 28, 2019