Nary Subramanian

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Software Architecture Adaptability An NFR
Approach

• Nary Subramanian
• Firmware Engineer
• Applied Technology Division
• Anritsu Company
• Richardson, TX.
• Email narayanan.subramanian_at_anritsu.com

• Lawrence Chung
• Dept. Of Computer Science
• Univ. Of Texas at Dallas
• Richardson, TX.
• Email chung_at_utdallas.edu

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Software Architecture Adaptability An NFR
Approach
Jini and the Programmer
Once a lucky and broad-minded programmer found a
Jini. Programmer I feel sorry for people in the
mid-east. Can you fix
that problem so that no more suffering
occurs? Jini I am sorry, but
that is something I cannot do. Programmer Then
will you fix my programs so that they
meet the needs of every single
user? Jini Give me the map - I
have a better chance at Middle
East! source Web
Moral Be Adaptable
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Software Architecture Adaptability An NFR
Approach
Adaptability Examples

• dual-mode cell phone
• command-processing system that accepts commands
  of different versions
• software system being able to operate on
  different OSs
• self-managing systems such as eLiza
• dynamic uploading of firmware

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Software Architecture Adaptability An NFR
Approach
Advantages of Adaptable Systems

• accomodate new requirements easily
• faster development of new software
• adding new software features
• fixing defects during maintenance phase (which
  consumes currently 50 of cost)

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Software Architecture Adaptability An NFR
Approach
What is Adaptability?

• No fixed definition
• Examples
• ease with which system may be adapted to changing
  requirements
• modifies behavior in response to changes in
  operating environment
• a software quality metric
• ...and many more ...

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Software Architecture Adaptability An NFR
Approach
Current Approach to Adaptability
State Problem problem is to develop adaptable
system that does xxx ...
Define Adaptability adaptability is evolution to
meet the needs of user and business
Develop solution Solution
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Software Architecture Adaptability An NFR
Approach
Some Drawbacks of Current Approach

• Lack of traceability of solutions to requirements
  why should Solution be adaptable? The usual
  justification is Solution does so-and-so and
  hence satisfies definition of adaptability.
• No way to analyze/explore alternative solutions
  what are other possibilities besides Solution
• No way to determine the degree to which system is
  adaptable

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Software Architecture Adaptability An NFR
Approach
The NFR Approach

• Applicable to any definition of adaptability
• Allows alternative solutions to be explored
• Decomposes adaptability depending on the domain
  
• Criticalities can be allocated to different NFRs
  of the decomposition
• Permits design tradeoffs
• Assessment of adaptability is possible

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Software Architecture Adaptability An NFR
Approach
Steps in The NFR Approach
Decompose Adaptability for the domain - NFR
softgoal hierarchy
Develop architectural alternatives - Design
softgoal hierarchy
Assign criticalities to various softgoals
Determine extent to which design softgoals
satisfice NFR softgoals - claim softgoal hierarchy
Choose the design components that satisfice the
relevant softgoals
Legend Down arrow go to next step Up arrow
iterate
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Software Architecture Adaptability An NFR
Approach
A Comprehensive Definition of Adaptability
Legend S,S old and new system E,E old and
new environment ?S,?E change in system,
environment
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Software Architecture Adaptability An NFR
Approach
Example SIG Development - Step 1 NFR
Softgoal Decomposition
SIG Softgoal Interdependency Graph
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Software Architecture Adaptability An NFR
Approach
Example SIG Development - Step 2 Design Softgoal
Decomposition
SIG Softgoal Interdependency Graph
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Software Architecture Adaptability An NFR
Approach
Final SIG SIG Softgoal Interdependency Graph
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Software Architecture Adaptability An NFR
Approach
Notation for SIGs
NFR Softgoal
Design Softgoal
OR-contribution
AND-contribution
Strongly-negatively satisficing
Negatively satisficing
Positively satisficing
Strongly-positively satisficing
Correlation Rule (negatively satisficing)
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Software Architecture Adaptability An NFR
Approach
Knowledge-Based Approach

• A KB of design goals, decomposition methods,
  correlations will make it easier to search for
  such items for future use.
• Currently even when such catalogs are available,
  they are not easy to use.
• NFR Approach allows for a knowledge-based
  approach
• Can be used to (semi-)automatically generate
  adaptable architectures

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Software Architecture Adaptability An NFR
Approach
Frame-like Notations
Design Softgoal
NFR Decomposition Method
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Software Architecture Adaptability An NFR
Approach
Frame-like Notations (contd)
Operationalization Method
Correlation Rule
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Software Architecture Adaptability An NFR
Approach
Summary

• Analysis of NFR adaptability
• Current techniques are not traceable to whys of
  software
• NFR Approach provides several advantages to
  developing adaptable architectures
• NFR Approach allows for a KB approach which will
  help generate architectures (semi-)automatically.

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Software Architecture Adaptability An NFR
Approach
Future Work

• Better cataloging of the NFR Adaptability and
  its refinements
• Develop methods for different domains so that KB
  is more useful to industry
• Develop procedure to generate architectures.