ISO 9000-4 1993 in Plain English

Guidelines for Managing Product Dependability Programs

ISO 9000-4 is OBSOLETE.  See ISO 9001 2015 and ISO 9004 2009.

This web page is based on the ISO 9000-4:1993 Quality Standard 
published by the International Organization for Standardization
It presents an interpretation of this standard using language 
that is simple and easy to understand.

ISO 9000-4 explains what a Product Dependability Program is and 
how it should be managed. Your organization should consider such 
a Program if dependability is an important aspect of product quality.


Product dependability policy and objectives 

  • Define and document your product dependability  policy and your product dependability objectives.

    • Define a policy that explains your attitude towards  product dependability and which specifies  dependability characteristics.                         

    • List the product dependability objectives you want to achieve.                                        

Functions and resources 

  • Define functions and provide resources.

    • Define the organizational functions and services that  you will need in order to manage and maintain your  Product Dependability Program.                      

    • Ensure that your Product Dependability Program has  all the resources it needs to carry out these functions  and perform these services.                                  

Dependability requirements and customer needs 

  • Product dependability requirements should be defined by researching customer needs and expectations.

    • Therefore market research procedures are needed.

Program review

  • Develop Program evaluation procedures.

    • Develop and document procedures that senior  managers can use to evaluate the performance  of your Product Dependability Program.

    • Develop and document procedures that independent groups can use to review product dependability performance, processes, procedures, tools,  tasks, results, and costs.                               

Program documentation 

  • Document your Product Dependability Program.

    • Document the methods and procedures  used to define dependability characteristics.

    • Document the methods and procedures  used to control dependability characteristics.

    • Document the methods and procedures  used to evaluate dependability characteristics.

Dependability measurement

  • Identify quantitative and qualitative tools to estimate  and analyze the dependability of your products.

    • Ensure that these tools are made available to staff.

    • Ensure that they know how to use these tools.

Information system 

  • Set up an information system to track  and store product dependability data.

  • Use this data to design and redesign your  products and to plan your maintenance activities.

and records 

  • Product dependability documents and records should  be maintained. These documents and records should  include product dependability:                                         

    • Plans 

    • Test data

    • Field data

    • Analyses

    • Predictions

    • Instructions

    • Requirements

  • Maintain a master list of program dependability documents  and records and make sure that only current authorized  versions are in circulation.                                        


  • Develop a product dependability plan. It should:

    • Explain how you intend to meet product  dependability requirements and objectives.

    • Describe the resources you will use to meet  your dependability requirements and objectives.

    • Define the steps you will take to meet your  dependability requirements and objectives.

Contract review 

  • Develop procedures to coordinate and control the  review of customer contracts. Your contract review  procedures should make sure that:

    • Dependability requirements are defined.

    • Operational expectations are clarified.

    • Maintenance obligations are specified.

    • Acceptance tests are described and explained.

    • Dependability differences, between the original  tender and the final contract, have been resolved.

    • Management representatives are appointed to  supervise and discuss contracts with customers.

    • Records are kept which describe review decisions.

Dependability requirements 

  • Define detailed product dependability requirements.

    • Define product availability requirements.

    • Define product reliability requirements.

    • Define product maintainability requirements.

  • Clarify your maintenance support assumptions.

  • Before you design products, make sure that product  dependability requirements are clarified and that  the design will meet these requirements.                   

Design and maintenance 

  • Develop product design and maintenance guidelines  to ensure that product dependability requirements are  met. These guidelines must:                                 

    • Address product reliability, maintainability,  and testability issues.                                     

    • Address the human factors that could  affect product dependability.                        

External products 

  • Develop procedures to define dependability
    requirements for products provided by outsiders.

    • Make sure that products provided by suppliers meet your product dependability requirements.             

    • Make sure that products provided by your customers clearly meet your product dependability requirements.

Analysis and review 

  • Evaluate product dependability. Analyze, predict, and review the dependability of your products. Consider using  the following kinds of tools and techniques:

    • Human factors analysis

    • Fault tree analysis

    • Tradeoff analysis

    • Stress analysis

    • Risk analysis

Verification and validation 

  • Verify and validate product dependability. Develop procedures  to verify and validate product dependability requirements. Consider using the following kinds of:

    • Planning procedures

      • Verification planning

      • Validation planning

      • Test planning

    • Testing procedures

      • Reliability tests

      • Production tests

      • Acceptance tests

      • Dependability tests

Life-cycle costs 

  • Calculate costs. Develop procedures to calculate  and analyze product life cycle costs.                  

Customer support 

  • Support your products. Make sure customers know how to:

    • Operate your products.

    • Maintain your products.

      • In order to ensure that your customers  properly maintain your products, make  sure they know what kinds of:                    

        • Spare parts should be used.

        • Test equipment should be used.

        • Maintenance tools should be applied.

        • Skills their maintenance people should have.

Dependability improvement 

  • Develop procedures to improve the dependability of  your products. Your procedures should ensure that  dependability improvement opportunities are identified  and exploited. Your procedures should try to:

    • Improve product reliability

    • Improve product availability

    • Improve product maintainability

  • Develop procedures to control the product dependability improvement process. Your procedures should ensure that:

    • Changes are reviewed.

    • Previous analyses are repeated.

    • Prior predictions are reconsidered.

    • Old data and documents are re-examined.

Dependability feedback 

  • Develop a product dependability feedback system.

    • Develop procedures to collect product  dependability data during:                    

      • Testing

      • Manufacturing

      • Field use

    • Develop procedures to handle, store,  and analyze product dependability data.

    • Develop procedures that customers can use  to collect product dependability data and to  report their experience back to you.

ISO 9001 2015 in Plain English - ISO 9004 2009 in Plain English


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Updated on November 29, 2014. First published on June 6, 1997.

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