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Optimizing Test Strategies with eXpress

by DSI Staff | Published 07/06/2004 | General

DSI International’s eXpress™ software has the following capabilities that were developed with test strategy optimization in mind:

  • Consolidate System Engineering data that can affect testing
  • Metrics and reports that expose test strategy shortcomings
  • Robust test definition, selection and ordering criteria
  • Data layering approach to reduce impact of engineering changes
  • Interoperability, to support concurrent engineering and early, iterative assessment
  • Top-down and bottom-up hierarchical integration
  • Hybrid function and failure mode model to support transition from concept to implementation

Optimization in eXpress can occur throughout the design process as a result of its inherent design. It’s support for optimization is solved through several key processes, identified here.


Reporting provides access to the wide range of metrics needed to assess the current or proposed diagnostic capabilities. Key reports that assist with test strategy optimization include:

  • Detection Order Report – Describes the fault detection capability of a diagnostic design and the overall (composite) reliability of the design.
  • Detection Coverage Report – Provides detailed data about detection tests within the associated diagnostic study, as well as a list of those functions and/or failure modes that are not detected within the study.
  • Fault Isolation Report – Describes the fault isolation capability of a diagnostic design and its performance under diagnosis, including basic maintainability metrics (MTTI, MTTR, Inherent Availability).
  • Fault Group Details Report – Provides detailed information for each fault group in a given diagnostic study, including the items, functions and failure modes that comprise the fault group, the failure probability associated with each function or failure mode in that fault group, the replacement cost and time associated with each item in the fault group, and the test sequence that results in isolation of the fault group.
  • Diagnostic Flow– Documents the diagnostic test sequence and isolated fault groups for the study.
  • Subset FD/FI Statistics – Provides information about the contribution of any particular element (or set of elements) towards the overall diagnostic performance at the same or higher level.


By generating assessments for a particular design configuration, design changes are both validated and considered as to their contribution towards an optimized solution. Sub-reports are also evaluated in support of a drill-down from the primary assessments. Evaluation of the assessments provides the knowledge as to whether to continue optimizing, roll-back the recent optimization, or stop optimizing altogether.


The structure of the eXpress model automatically updates much of the model in response to more fundamental changes. This allows more rapid updates, and therefore more alternatives to be assessed, in support of alternatives exploration.

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