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Software Dependability Modeling

Lead Personnel: LiGuo Huang

Objectives: Develop a ďvalue-basedĒ model for understanding and evaluating software dependability alternatives and the tradeoffs among them, together with methods and tools for evaluating and improving dependability at both design- and run-time. Such model makes explicit the idea that a given system dependability must be evaluated, not in absolute terms, but in terms of the value that it provides the stakeholders.

Approach: Define dependability as a composite property that integrates such attributes as availability, reliability, safety, security, survivability and maintainability. Develop an Information Dependability Attribute Value Estimation (iDAVE) model for reasoning about the return on investment (ROI) of software dependability investments. It integrates cost estimating relationships (CERís) from the Constructive Cost Model COCOMO® II; dependability estimating relationships (DERís) from the Constructive Quality Model COQUALMO; and value estimating relationships (VERís) supplied by the systemís stakeholders. The other related models such as quality attribute requirement conflict calculation (QARCC), and software defect dynamics modeling will be added into the model as appropriate. The assumption made by this model is:

  • The iDAVE modelís initial dependability value estimating relationships (VERís) assume that a baseline business case analysis has been performed for various components of value (profit, customer satisfaction, on-time performance) as a function of the time-phased information processing capabilities at nominal dependability attribute levels.

Use the baseline dependability level as the start point and increase the dependability investment level from the baseline dependability level. Then analyze the higher-payoff and lower-payoff regions of a projectís dependability investment. Develop a tool helps user to do such analysis.

Please click iDAVE to download the initial spreadsheet version of the iDAVE Tool.


  1. D. Port, L. Huang, "Software Dependability Risks and the Insurance Process," The 5th International Workshop on Economics-Driven Software Engineering Research, May 2003.
  2. L. Huang, B. Boehm, "Reasoning about the Value of Software Dependability: the iDAVE Model," to appear on Supplementary Proceedings 14th. IEEE International Symposium on Software Reliability Engineering (ISSRE),  November 2003.

Future Plans:
Further calibrate iDAVE to JPL experience, and to experimentally use the model to evaluate the relative ROI of alternative combinations of dependability technologies to planetary mission outcomes. Develop and calibrate domain-oriented DERís and VERís for additional dependability attributes such as security, safety, accuracy, and performance assurance

Develop MDS-Based Extensions of the USC Information Dependability Attribute Value Estimation (iDAVE) Model.