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What is Dependability?


Dependability sounds like Reliability. Are they not the same?


Relationship of Dependability to Quality


Relationship of Dependability to Integrity


Relationship of Dependability to Safety and Security applications


What standard are prepared by TC 56?


Why are TC 56 standards important?


How do TC 56 standards apply to my project?


TC 56 standards structure


How are TC 56 standards developed?


How are TC 56 standards maintained to keep up-to-date?


Are TC 56 standards used for compliance purposes?


1.   What is Dependability?

Dependability is the ability of a product to do its job when required and for the duration we wanted without encountering problems. Dependability reflects something in the product that has earned our trust. It means that the product we could rely on when we needed it to perform its intended task. And that something is the unique property of dependability in the product. They include: 

  1. Reliability – the longevity of the product to do its job without failures.
  2. Maintainability – the ease of keeping the product in good running condition.
  3. Maintenance – all actions undertaken to retain an item, or restore and item, to an operational state. 
  4. Maintenance Support – provision of resources (human, equipment, material, parts, facilities and information) to maintain an item. 
  5. Supportability – maintenance and logistic activities to retain an item, or to restore an item, to an operational state. 

These are influencing factors of dependability on product performance. They are sometimes known as dependability performance characteristics.

The formal definition of dependability and other related dependability terms can be found in IEC 60050-192 available from IEC.

Product dependability does not happened by itself. Dependability needs to be designed and built into the product. Dependability performance needs to be assessed to determine its acceptance for specific applications. Performance records providing dependability history are the testimony to gain our confidence in using the product. Dependability activities need to be managed. Detailed information on dependability management can be found in IEC 60300-1.


2.   Dependability sounds like Reliability. Are they not the same?

No. Dependability is more than just reliability alone. Reliability only deals with a product performing its intended function without failure for a given period of time. Dependability performance is all encompassing including reliability. Reliability is a probability measure of random failures. Random failure could occur within the first hour of product operation or towards the end of life of the product. Unless the product is self-healing when failed, it would require some form of intervention or interaction to keep the product running. Addressing reliability only in product specification could lead to costly maintenance effort. To fully specify dependability we need to address not only reliability, but also maintainability and maintenance support.


3.   Relationship of Dependability to Quality

Dependability is a time-dependent characteristic of quality. Quality is defined as the degree to which a set of inherent characteristics fulfills requirements as per ISO 9000. As an assurance function, Dependability complements Quality by providing the needed time related performance measures in product quality for specific applications.


4.   Relationship of Dependability to Integrity

Dependability embraces the concept of Integrity in designing and building a dependable product. Integrity is an inherent property of the components selected to build a product that could withstand external tempering or resist intrusion to minimize risk exposure.  

TC 56 deals with Dependability from a system availability performance perspective. JTC1/SC7 deals with Software and System Engineering by focusing on risk containment and mitigation processes to enhance product integrity. There are common life cycle processes shared by TC 56 and JTC1/SC7 in dealing with Dependability and Integrity issues. 

Product dependability is achieved by addressing reliability, maintainability, and maintenance support to optimize availability performance. Dependability is measured by observed product performance data in terms of uptime or downtime, failure rate or mean-time-between-failures. Product integrity is achieved through robust design architecture and construction, and the needed degree of design rigour and mitigating processes for risk containment. Integrity is measured in comparative terms of a defined level of acceptable risk.


5.   Relationship of Dependability to Safety and Security application

The scope TC 56 does not cover safety or security areas. There are other IEC standards addressing specifically on safety and security issues. Dependability, as a technical discipline for assurance sciences may raise related issues and share common methods for risk analysis in safety and security applications. 


6.   What Standards are prepared by TC 56?

Click here to see list of standards prepared and maintained by TC56.


7.   Why TC 56 standards are important?

TC 56 Dependability standards set the framework for establishing Dependability management systems in an organization, whether it is a large corporation or a small business enterprise. TC 56 standards provide guidelines for dependability management to maximize the benefits of applying timely dependability disciplines and best practices in product development and in service provision to meet competitive global market demands.   

TC 56 standards complement ISO 9000 series of Quality standards to deal specifically with the time-dependent issues that are critical in achieving business/project success. These are performance issues are related to the delivery of dependable products and customer satisfaction. They are influenced by contributing factors in reliability, maintainability, and maintenance support. The challenge of dependability as reflected in many of the TC 56 standards is to help optimize investment planning, source selection, and effective project implementation to minimize business risk exposures. This leads to reduce long-term ownership costs by judicious application of life cycle processes.  

Dependability standards are used in business contracts. They provide common understanding of terminology to facilitate international trade. Dependability standards provide assessment methods and practical measures to ensure the successful outcome of product dependability and quality of service.

Dependability standards are non-prescriptive. They are used as guidance on application of proven dependability techniques and tools during the various product life cycle phases for continual improvement.


8.   How do TC 56 standards apply to my project?

Dependability projects generally deal with product performance to meet user needs and strive to satisfy the customers. A product has its life cycle phases: from concept and definition, through design and development, manufacturing, installation, operation and maintenance, to its final discontinued use and disposal. The project of interest may involve any phase or phases of the product life cycle. TC 56 standards are organized for ease of identification and implementation by grouping the relevant standards in a simple hierarchy. Such arrangement is reflected in the          TC 56 standard structure to facilitate user information access. Guidance in standard selection and application is provided in IEC 60300-1


9.   TC 56 standards structure

TC 56 standards are divided into 3 categories:

  • Core standard – standard providing overview on dependability fundamentals, objectives or management.
  • Process standard – standard giving guidance on a particular dependability issue related to an aspect of management or to a life cycle phase.
  • Support standard – standard giving technical information of general relevance in various dependability issues.
  • Associated standard – standard in which TC56 has contributed, but is not directly responsible for its development.

Click here to see list of standards prepared and maintained by TC56.


10.   How are TC 56 standards developed?

TC 56 standards are developed by consensus with contributions from participating National Committee (NC) experts on the subject. A New Proposal (NP) is prepared and circulated to seek NC support when the subject of standardization is considered important to industry. A Working Draft is normally submitted along with the NP to provide sufficient information to justify initiation of the standard work. Upon approval by the NC in voting on the NP, the TC 56 Secretary will assign a project number to a responsible Working Group or a dedicated Project Team to initiate the work. The standard development process takes about 3 to 5 years from NP, through Committee Draft (CD) and Committee Draft in Voting (CDV) to reach its Final Draft International Standard (FDIS) stage before its publication as an International Standard (IS) bearing a unique IEC number.


11.   How are TC 56 standards maintained to keep up-to-date?

TC 56 standards are maintained to keep up-to-date by means of a maintenance process. It takes into account the anticipated future needs of industry to ensure that TC 56 standards meet those needs. The Maintenance Teams are established in each of the TC 56 Working Groups and have experts nominated by the National Committees assigned to review and revise the standard for maintenance purposes. A process for voting confirmation or withdrawal is put in place for the standard going through the maintenance process. Each candidate standard is subject to a maintenance review within a 5-year period.


12.   Are TC 56 standards used for compliance purposes?

TC 56 standards are non-prescriptive. They are not intended for compliance purposes. However, TC 56 standards may be referenced in business contracts for their technical guidance and recommended methods.

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