An Architecture for Constructing SelfEvolving Software Systems

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An Architecture for Constructing Self-Evolving
Software Systems

• By Nelson Azadian

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Consider the Following

• An enemy target fires an unidentified projectile
  at a military installation.
• The military installation is guarded by a missile
  defense system which has only seconds to respond.
• What should the system do?

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Possible Courses of Action

• One possible course of action entails the missile
  defense system firing a barrage of missiles in
  hopes of intercepting the enemy projectile.
• Yet another course of action entails the missile
  defense system performing a quick analysis of the
  projectile, whereby tailoring itself as well as
  its response to the projectile based off of its
  pre-analysis.

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Self Evolving Software Systems

• The second course of action in the previous slide
  was an example of a Self Evolving Software
  System.
• Systems of a self evolving nature automatically
  evolve in order to better handle ever changing
  external or internal circumstances.

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By Evolve We Mean

• The replacement or removal of software modules
  with alternate software modules.
• The removal or addition of system constraints.
• In other words, by evolution we mean changes to
  the system at an architectural level.

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Self Evolving Software Systems

• Domain Repository
• Architectural Model
• Evolution Engine
• Architectural Abstraction Layer

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Domain Repository

• The Domain Repository stores the alternate
  solutions (software modules) to a given
  application domain.
• The Domain Repository also stores information
  about the structure, behavior and design
  tradeoffs (performance, requirements,
  limitations, etc) of these alternate solutions.

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Architectural Model

• The Architecture of the system must lend itself
  to a reflection of the systems current goals,
  structure, and design rationale at any given
  time.
• The Evolution Engine uses this information in
  order to understand the current goals of the
  system and under what assumptions the system
  believes it can achieve them.

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Evolution Engine

• The Evolution Engine sits alongside the system
  monitoring whether the system is meeting its
  goals.
• The Evolution Engine detects any exceptional
  conditions, diagnoses the underlying causes to
  these exceptions and enacts an evolution plan (a
  change to the system) in order to resolve them.

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Architectural Abstraction Layer

• The Architectural Abstraction Layer allows the
  Evolution Engine to modify the architecture of a
  system at high level.
• In other words, the Architectural Abstraction
  Layer provides the Evolution Engine with an
  interface in which to modify the systems
  architecture.

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Uses

• Self Evolving Software Systems are primarily used
  in highly volatile time critical domains.
• Examples include
• Missile Defense Systems
• Reactor Control Systems
• Flight Control Systems

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Current Tools

• xADL 2.0 which represents system architectures in
  an XML format.
• ArchStudio 4 which is used to help manage
  architectural repairs and changes at an
  architectural level.

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References

• An Architecture for Constructing Self-Evolving
  Software Systems, Dellarocas Chrysanthos, Klein
  Mark, Shrobe Howard.
• A Constraint Architectural Description Approach
  to Self-Organising Component-Based Software
  Systems, Waewsawangwong Pakorn.
• Towards Architecture-Based Self Healing Systems,
  Dashofy Eric, Hoek Andre van der, Taylor Richard.
• Self-Managed Systems an Architectural Challenge,
  Kramer Jeff, Magee Jeff.

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Questions