Design and Evaluation of Software Architectures
Barbora Biihnová
Faculty of Informatics, Masaryk University Brno, Czech Republic
LaSArIS Seminar October 15, 2009
,1/
Series of seminars on software architecture
•  Overview of Software Architecture (SA)
Definition of SA, topics and concepts of SA, CBSE
•   Design and Evaluation of Software Architectures
Architecture requirements, design process, evaluation of quality attributes
•  The PCM Design and Evaluation Framework
Architecture design, performance prediction, reliability evaluation
Notice: Some of the slides are inspired by Software Architecture lectures of Uni Karlsruhe, ©R. Reussner
O Introduction
Why software architectures?
What is a software architecture?
What should be part of architecture design?
© Requirements
Functional and extra-functional
Q Design of S A
Architectural models Developer roles Development process
O Evaluation of SA
Quality attributes of SA
@ Conclusion
,1/
Evaluation of SA
Why software architectures?
• How to bridge the gap between requirements and code?

Design and Evaluation of Software Architectures
Evaluation of SA
The role of software architecture
•  System-level abstractions
•  Coarse-grained structure of the system

Design and Evaluation of Software Architectures
Three core views that need to be described
•   Module view = system components
i.e. computational software units, often concurrent (tasks, threads)
•  Connector view = communication styles
e.g. pipe-and-filter, shared-data, publish-subscribe, client-server (synchronous vs. asynchronous)
•  Allocation view = mapping to hardware (or software) resources
Three main activities in architecture design
•   Requirements specification Functional and extra-functional
•   Design of the architecture Architectural models Developer roles Development process
•   Evaluation of the architecture Quality attributes of SA
,1/

Why software architectures?
What is a software architecture?
What should be part of architecture design?
Requirements
Functional and extra-functional
Architectural models Developer roles Development process
ď\    Pw-.li
)utes of SA
Conclusion
,1/
rement.
Functional requirements
•   Execution of serviceAO should not need more than 10 other components.
•   Each opened transaction needs to be closed before the component starts another one.
•  A component must not get blocked when executing a service.
Extra-functional requirements
•   Guaranteed response time (in X% of cases)
•  Availability of X% within each month
•   Hardware or software compatibility
\iu^

Why software architectures?
What is a software architecture?
What should be part of architecture design?
Requirements
Functional and extra-functional
Design of S A
Architectural models Developer roles Development process
ď\    Pw-.li
)utes of SA
Conclusion
,1/
•   Module view = system components
1.   Static structure model
•  Connector view = communication styles
2.   Dynamic process model
•  Allocation view = mapping to hardware/software resources
3.   Deployment model
What about the design of a single component, and information needed for the evaluation of the design?
•  Component developer
Implementation and documentation of individual components
•  Software architect
Static structure and dynamic proc. models of the architecture
System deployer Deployment model
•   Domain expert
Usage scenarios for the system
•  Quality manager
Evaluation model of architecture quality
^SMrS^
A general architecture development process
O Identify system components
@ Identify component interfaces
O Design connectors
O Identify partitions that should be allocated to the same host
© Validate/evaluate the architecture
,1/
Top-down approach
•   Levels of refinement - third-party components, coded components, model-driven refinement
Bottom-up approach
•   Libraries of components - design for reusability, own vs. third party components
Good practices
•  Architectural patterns
•   Measures of design quality
•   Correctness by construction                                                          /"
Why software architectures?
What is a software architecture?
What should be part of architecture design?
squirements Functional and extra-functional
Architectural models Developer roles Development process
O Evaluation of SA
Quality attributes of SA
@ Conclusion
,1/
Quality attributes of SA
•  Qualitative vs. quantitative attributes
•   Functional vs. extra-functional attributes
Extra-functional quality attributes
•   Performance - throughput, response time, deadlines
•   Reliability - failure-free operation, HW and SW propagation
•  Availability - software and hardware
•  Security - authentication, authorization, encryption, integrity Scalability - request load, simultaneous connections, data size
•   Modifiability and maintainability                                            /'"
Methods of quality evaluation
•   Monitoring and testing - not exhaustive, better after implementation, possible also in model simulation
•  Quality prediction - good for quantitative attributes, for both design and run time
•   Formal verification - good for qualitative attributes, for both design and run time
Limits of automated methods
•  Time and memory consuming
•   Need to be executed on system abstraction
Why software architectures?
What is a software architecture?
What should be part of architecture design?
squirements Functional and extra-functional
esign of SA Architectural models Developer roles Development process
ď\    Pw-.li
)utes of SA
Conclusion
,1/
What should be part of architecture design?
•   Requirements specification
Functional and extra-functional
•   Design of the architecture
Architectural models Developer roles Development process
•   Evaluation of the architecture
Quality attributes of SA
Thank you for your attention! Any questions?

-£/