The document outlines the distinction between functional and non-functional requirements in software architecture, emphasizing that functional requirements describe what a system should do, while non-functional requirements specify how a system should be. It details various system quality attributes from different perspectives, such as performance, security, and operations, which measure the suitability and effectiveness of a software product. Additionally, it highlights the importance of these attributes in guiding architectural decisions and ensuring compliance with technical and business standards.

1. F U N C T I O N A L / N O N F U N C T I O N A L R E Q U I R E M E N T S A N D
S O F T W A R E A R C H I T E C T U R E M E A S U R E O F T E A M
E M P H A S I S O N T R A D E O F F D E C I S I O N S
A D N A N M A S O O D
S R . S O F T W A R E A R C H I T E C T & D O C T O R A L C A N D I D A T E
B L O G . A D N A N M A S O O D . C O M
A D N A N . M A S O O D @ O W A S P . O R G
System Quality Attributes
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2. Definition
“Software Quality Attributes are the benchmarks that
describe system’s intended behavior within the
environment for which it was built. The quality
attributes provide the means for measuring the
fitness and suitability of a product. Software
architecture has a profound affect on most qualities
in one way or another, and software quality
attributes affect architecture.”

3. Functional Requirements
 In general, functional requirements define what a
system is supposed to do
 usually in the form of "system shall do <requirement>“
 Functional requirements define specific behavior or
functions.
 The plan for implementing functional requirements
is detailed in the system design.

4. Non-Functional Requirements
 Non-functional requirements define how a system is
supposed to be.
 Non-functional requirements specify criteria that
can be used to judge the operation of a
system, rather than specific behaviors.
 The plan for implementing non-functional
requirements is detailed in the system
architecture.

5. System Quality Attributes
 Non-functional requirements specify system
quality attributes.
 Other terms for non-functional requirements are:
 Constraints
 Quality attributes
 Quality goals
 Quality-of-service (QoS) requirements
 Non-behavioral requirements
 Informally, these are known as the “-ilities"

6. System Quality Attributes
Business Perspective
 Suitability: Functionality is suitable to all end users
 Compliance: Functionality is compliant with applicable regulatory
guideline
 Certifiability: System is able to be certified to some standard by an
independent third party
• Conformance: Conformance to industry and operational
standards
 Accessibility: The user interface can be accessed and utilized by differently
abled users
 Adaptability: Ability to change the system components to meet
new business needs
 Extensibility & Modifiability: Ability to easily add new features
and customizations
 Replaceability: Ability to replace system in the future
 Reporting: The system supports generating various reports

7. System Quality Attributes
Security Perspective
 Security: System is secure:
confidentiality, integrity, availability, accountability and
assurance
 Privacy: System does not reveal (or allow revealing) of
information to improper parties
 Non-exploitability: The system, its components, and its
configurations are hardened against known and
unknown security vulnerabilities
 Accountability: The system records all user interactions
and data changes
 Auditability: The system makes accountability
information available to managers and operators

8. System Quality Attributes
Performance Perspective
 Efficiency: System does not waste valuable resources
 Performance: Perceived response is immediate
 Scalability: Able to handle increased usage on the
appropriate amount of resources, able to add resources
quickly and easily to handle increases in demand
 Responsiveness: The system responds to interactions
with minimal delay and/or latency
 Capacity: The system can handle sudden peaks and
surges in demand
 Throughput: The system can handle a specified number
of interactions or transactions within a specified duration
without undesirable degradation in terms of other
qualities

9. System Quality Attributes
Configuration Perspective
 Configurability: Ease of making configuration changes
 Integrity: The system, its configuration, and its data
cannot be changed by unauthorized
parties(including accidental or deliberate
misconfiguration)
• Deployability: Ease of
installation, reinstallation, and updating
 Portability: System supports changes in choice of
underlying technologies and architectures (such as
database platform, operating system platform, etc.)
 Interoperability & Compatibility: Functionality
interoperates with other systems easily

10. System Quality Attributes
Operations Perspective
 Availability & Fault Tolerance: System continues operating properly in the event of failure by
one or more of its components
 Isolation: System survives and gracefully handles situations in which dependent “downstream”
systems become unavailable
 Continuity: System recovers from failures in surrounding environment
 Disaster Recoverability: The system, its data, and its configuration can be completely and
quickly recovered from backups and configuration management repositories, even in the event
of a catastrophic loss of a data center
 Operability: System can readily be kept in a functioning and operating
condition by manual or automated means
• Maintainability: System upgrades can quickly and safely be performed with a
minimum of downtime
• Monitorability: Ability for operators to easily see how the system is operating
• Alerting: The system notifies operators of faults and exceptional conditions
• Maturity: System components are proven stable by others
• Stability and Reliability: The system exhibits infrequent failures

11. System Quality Attributes
Data Perspective
 Durability: The system does not lose critical operational data, whether “in-
flight” or “at-rest”
 Reversibility: Undesirable system and data changes can be reversed quickly
and easily with minimal disruption to the business
 Cacheability: The data is structured with appropriate separation of volatile
(changing) and non-volatile data to support caching
 Archivability: Older data can be relocated to separate data stores
 Partitionability: The system supports splitting like-kind data across
multiple databases (for scalability, risk mitigation, etc.)
 Idempotency: Interactions performed twice result in same change as if
performed once
 Concurrency: The system supports a high degree of simultaneous
interactions with the database without degrading in performance or
sacrificing data integrity (ex: optimistic locking, snapshot isolation)
 Backup : The database and message queues support being backed up
without the system being taken offline

12. System Quality Attributes
Diagnostics Perspective
 Supportability: System operators can quickly and easily
identify faults and perform root cause analysis within an
environment of controlled access to information and
restricted privileges
 Instrumentability: System is capable of recording various
operational metrics that can be analyzed and reported
on
 Traceability: System can be configured to record its own
interactions with itself in order to aid support personnel
in diagnosing problems
• Logging: The system logs external and
interactions with configurable degrees of detail

13. System Quality Attributes
Enhancement Perspective
 Analyzability: Ability to figure out how the
system functions
 Documentability: Ability to communicate
about the system in writing
 Understandability: Able to use system with little
training
 Learnability: Supports learning of system functionality
with little external interfacing
• Testability: Ability to create repeatable and
specific tests of the system and potential for
some to be automated

14. Software Quality Attributes Ratings Tool
http://www.gettingagile.com/wp-content/uploads/2009/05/softwarequalityattributes-ratingtool.xls OR
http://bit.ly/1aIPeU1

15. References
Getting Agile
http://www.gettingagile.com/2009/05/17/survey-for-
software-quality-attributes-where-should-we-focus/
MSDN – Quality Attributes
http://msdn.microsoft.com/en-us/library/ee658094.aspx
Implementing System Quality Attributes
http://msdn.microsoft.com/en-us/library/bb402962.aspx
Operational Aspects of a System – ACM Queue
http://queue.acm.org/blogposting.cfm?id=56822
about software engineering
about software industry
architect software
architecture software
architecture software programs
design and software
design and user experience
design for user experience
design user experience
enterprise architect
enterprise architects
enterprise it architect
it quality assurance
management quality system
program quality
quality assurance
quality assurance for software
quality assurance in software
quality assurance software
quality in software
quality program
quality software
quality system
quality systems management
requirements software
software architect
software architect software
software architects
software architectural
software architecture software
software business
software development cycle
software engineering
software engineering by
software for quality assurance
software for software engineering
software metrics
software quality
software quality assurance
software quality assurance software
system architect
systems quality
systems quality management