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Dependability . ITV Model-based Analysis and Design of Embedded Software Techniques and methods for Critical Software Anders P. Ravn Aalborg University August 2011. Basic Concepts. Availability : readiness for correct service. Reliability : continuity of correct service.

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dependability

Dependability

ITV Model-based Analysis and Design of Embedded Software

Techniques and methods for Critical Software

Anders P. Ravn

Aalborg University

August 2011

basic concepts
Basic Concepts
  • Availability: readiness for correct service.
  • Reliability: continuity of correct service.
  • Safety: absence of catastrophic consequences.
  • Confidentiality: absence of unauthorized disclosure of information
  • Integrity: absence of improper system alterations.
  • Maintainability: ability to undergo modifications.
development phase and faults
Development Phase and Faults
  • the physical world with its natural phenomena,
  • human developers, some possibly lacking competence or having malicious objectives,
  • development tools: software and hardware used by the developers to assist them in the development process.
  • production and test facilities.

Fault

* prevention ?

* tolerance ?

* removal ?

* prediction ?

use phase and faults
Use Phase and Faults
  • the physical world with its natural phenomena,
  • administrators (including maintainers): entities (humans or other systems) that have the authority to manage, modify, repair and use the system; some authorized humans may lack competence or have malicious objectives;
  • users: entities that receive service from the system at their use interfaces;
  • providers: entities that deliver services to the system at its use interfaces;
  • infrastructure: entities that provide specialized services to the system, such as information sources (e.g., time, GPS, etc.), communication links, power sources, cooling airflow, etc.
  • intruders: malicious entities that attempt to exceed any authority they might have and alter service or halt it, alter the system’s functionality or performance, or to access confidential information. Examples include hackers, vandals, corrupt insiders, agents of hostile governments or organizations, and malicious software.

Fault

* prevention ?

* tolerance ?

* removal ?

* prediction ?

means
Means

Fault

prevention

removal

prediction or forecasting

tolerance

fault prevention
Fault prevention
  • Systematic procedures
  • Clean room (Harlan Mills)
  • Inspection
  • Reviews
fault p revention
Fault prevention
  • process (activities)
  • notations
  • tools
  • Careful Design
  • Conservative Design
  • robust functionality
  • testability
  • tracability
fault removal
Fault Removal

In Development

In Use

Preventive maintenance

Corrective maintenance

Fault isolation

  • Verification and validation
  • Diagnosis
  • Correction
fault forecasting
Fault forecasting
  • Qualitative evaluation
  • Quantitative evaluation

Models: Markov-processes, Fault-trees, ...

fault forecasting1
Fault Forecasting
  • Calculation – analysis of design
  • Simulation – measurement on design
  • Test -- measurement on implementation
exercise
Exercise
  • Where would you add prevention, removal and forecasting in a V-model process?
  • What would you add?

Requirements Spec --------------------------- Accpt. Test Report

Acceptance Test Spec

Architectural Spec ------------------------ Integr. Test Report

Integration Test Spec

Module Interface Spec

Module Spec ------------------- Module Test Report

Module Test Spec

Program Source text