An ArchitectureBased Approach to SelfAdaptive Software

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An Architecture-Based Approach to Self-Adaptive
Software
Authors Loads of them but importantlyNenad
MedvidovicOthersOreizy, Gorlick, Taylor,
Heimbigner, Johnson, Qullici, Rosenblum Wolf

• Presented by
• Chirag Rajyaguru
• Niraj Motwani

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An Architecture Based Approach to Self-Adaptive
Software

• Architecture
• Approach
• Self
• Adaptive
• Software

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Architecture Approach

• Architecture The overall design or structure of
  a computer system, including the hardware and the
  software required to run it, especially the
  internal structure of the microprocessor
• Approach make a proposal or overtures to with a
  specific end in view

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Self, Adaptive Software

• Self Here On ones own
• Adaptation Something, such as a device or
  mechanism, that is changed or changes so as to
  become suitable to a new or special application
  or situation
• Software The programs, routines, and symbolic
  languages that control the functioning of the
  hardware and direct its operation.

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What is Self Adaptive Software??

• E. Grishikashvili CMU The Software which can
  identify, promote and evaluate new models of code
  design and run-time support which allow software
  to modify its own behavior or order to adapt, at
  runtime, when exact conditions and inputs are
  known, to discovered changes in requirements,
  inputs, and internal/external conditions.
• Paul Robertson MIT A self-adaptive system is
  a system that continually (at runtime) monitors
  its success in achieving its intended goal.  When
  the system is found to be doing poorly the
  systems modifies itself in an attempt to do
  better at its assigned task.  A self-adaptive
  system presupposes that there are multiple ways
  of achieving the same task and that in some
  contexts one method may be better suited than
  another.

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Question !!!!

• Does Self-Adaptation mean Adding something like
  INTELLIGENCE!! ? I hope I dont get slain for
  using this word in this class

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Important Properties

• High Dependability Robustness
• Adaptability Availability
• Consistency Correctness
• Safety Reliability
• !!!!!! Other properties are important !!!!!!
  depending on the applications requirements but
  these are the basic important properties
  according to the author(s) !!!!

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Several Issues to take care of!!

• When ?
• Open-adaptive / closed-adaptive ?
• Fully automatic/ self-contained/ human-in-loop
• Cost effectiveness
• Adaptation Policy lazy/opportunistic/continuous

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Issues contd.

• Good enough ness of information
• Frequency of adaptation

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How to?

• Online Algorithms
• Algorithm Selection
• Evolutionary Programming and machine-learning
  techniques

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General Purpose Approach to self-adaptive systems
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Many Dependencies Interdependencies

• Software agents that automate the task within the
  process
• Software components respective environmental
  assumptions
• Environment where the s/w is deployed
• Messaging and event services that are used for
  various connections

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Architectures

• C2
• Weaves
• Commonalities
• Distinguish Component Connector
• No restriction on the language to be used
• Communication via Asynchronous messages
• Single or multiple threads / component

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C2
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Weaves
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C2 vs. Weaves

• C2 has been optimized for flexible components
• Weaves focuses on high-performance, flexible
  connectors

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Dynamic Code Updatinga Beginning / an end

• Dynamic Code update / Migration of Component not
  more than a big step
• Example Removing Guidance Component from
  Missile is Migration of a component but that will
  Marr the functionality of the system

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Evolution Management

• Safety
• Reliability
• Correctness
• To guard against untoward change AEM was
  introduced. AEM(architecture evolution manager)
  mediates all change operations directed toward
  the architectural model. Ensures ACID properties
  on Architectures structural changes.

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Methods of implementing Changes

• Following methods can be used
• Visual
• Interactive
• Architecture editor

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ADAPTATION MANAGEMENT

• Adaptation management describes the life cycle of
  adaptive software systems.
• Collecting observations (Observers).
• Monitoring and evaluating the application, and
  its operating environment.
• Planning adaptations (Planners).
• Deploying change descriptions to the running
  application (Deployers).

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Managing Self Adaptive Software

• Requires variety of agents
• Observers, planners and deployers.
• Infrastructure support to host the agents and
  support the various activities of adaptation
  management in form of registries.
• Registries contain resource descriptions,
  configurations and other declarative information.
• Registries providing standard interface by which
  agents can query and manipulate the contents of
  registry, which acts as blackboard for exchanging
  information.
• Eg. Software Dock, University of colorado,
  Boulder- infrastructure element for distributed
  configuration and deployment of software systems.

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Life Cycle of Adaptive Software Systems
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Collecting Observations

• Embedded assertions (inline observers).
• Responding to event patterns (Expectation agent).
• Monitoring events occuring outside of the
  application.
• Provisions for human observers.

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Evaluating Monitoring

• Needed for Consistency Management.
• Inconsistencies can occur when some architecture
  element behaves in a manner inconsistent with the
  behavior required of it. How to we maintain
  consistency?
• Static Analysis eg. Attributed graph grammars.
• Dynamic Analysis Runtime checks to detect
  inconsistencies.
• Hybrid Approach.

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Planning Changes

• Observation planning
• Determine which observations are necessary for
  deciding when and where adaptations are required.
• Adaptation planning
• Determine which adaptations to make and when to
  make.

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Deploying Change Descriptions

• It is the coordinated conveyance of change
  description, components and possibly new
  observers or evaluators to the implementation
  platform in the field.
• Change agents propagate and move out among sites
  to carry out their tasks carrying with them
  change descriptions.
• Change descriptions may include new components or
  connectors and their affiliated annotations.

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Conclusions

• Separating concerns of software adaptation from
  function facilitates their independent analysis
  and evolution.
• Ensuring that changes made to architectural model
  is consistent with its implementation-
  consistency maintenance.
• Change management to ensure system integrity.
• Neat categorization of Evolution management and
  Adaptation management as two separate processes
  and highlighting their activities.
• The paper says architecture based approach and
  is very well confined to its scope.

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Prism for Self Adaptive Software

• Architectural Styles
• Characterized in terms of external structure,
  topology rules, behavior, interaction and data
  flow.
• Architectural requirements to support self
  healing behavior.
• Adaptability
• Dynamicity
• Awareness
• Observability
• Autonomy
• Robustness
• Distributability
• Mobility
• Traceability

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Prism for Self Adaptive Software

• Architectural style meets adaptability
  requirement.
• Distributability achieved via border connectors.
• Meta level components facilitate dynamicity,
  awareness, mobility and robustness.
• Some meta level component like AEM could be
  developed in PRISM to ensure ACID properties.
• Traceability ensured via an architectural
  middleware implementation.
• Observability and autonomy can be worked on.