We shall try to define and understand some of the terms used in quality management system. The standard ISO 9000:2005 is the basis on which the terms are defined.
5) Terms relating to Characteristics
Terms relating to Characteristics have following definition:
ISO 9000 definition:
NOTE 1 A characteristic can be inherent or assigned.
NOTE 2 A characteristic can be qualitative or quantitative.
NOTE 3 There are various classes of characteristic, such as the following:
- physical (e.g. mechanical, electrical, chemical or biological characteristics);
- sensory (e.g. related to smell, touch, taste, sight, hearing);
- behavioral (e.g. courtesy, honesty, veracity);
- temporal (e.g. punctuality, reliability, availability);
- ergonomic (e.g. physiological characteristic, or related to human safety);
- functional (e.g. maximum speed of an aircraft);
A characteristic is a distinctive feature or property of something.A distinguishing feature, dimension or property of a process or its output (product) on which variable or attribute data can be collected. Characteristics can be inherent or assigned. An inherent characteristic exists in something or is a permanent feature of something, while an assigned characteristic is a feature that is attributed or attached to something. In a product, a characteristic is a dimension or a physical, chemical, electrical, mechanical or visual property. A characteristic must be measurable, either directly or indirectly, either variable or attribute. Attribute characteristics are qualitative data that is measured or checked and results in conformance or non-conformance, pass or fail.
5.2) Quality characteristic
ISO 9000 definition:
“Inherent characteristic of a product,process or system related to a requirement.”
NOTE 1 Inherent means existing in something, especially as a permanent characteristic:
NOTE 2 A characteristic assigned to a product, Processor System(e.g. the Price of a Product, the owner of a Product)is not a quality characteristic of that product, processor system.
A quality characteristic can be define as an inherent feature or property exists in the product or is a permanent characteristic of product.A quality characteristic is tied to a requirement and is an inherent feature or property of a product, process, or system. A requirement is a need, expectation, or obligation. It can be stated or implied by an organization, its customers, or other interested parties. Price of the product and the owner of the product are not part of the product characteristic. Special Product Characteristic are those quality characteristic for which reasonably anticipated variation could significantly affect a product’s safety or compliance with governmental standards or regulations, or is likely to significantly affect customer satisfaction with a product. It can be further divided into into two categories: Critical Characteristics and Significant Characteristics.Critical Characteristics are defined as product or process requirements that affect compliance with government regulation or safe product function, and which require special actions or controls. Significant characteristics are those quality characteristics other then Critical characteristics which are important to customer satisfaction and thus require special controls. Companies have not standardized a method for grouping and denoting Special Product Characteristics. Nomenclature and notation will vary.
ISO 9000 definition:
“Collective term used to describe the availability performance and its influencing factors: reliability performance, maintainability performance and maintenance support performance.”
NOTE: Dependability is used only for general descriptions in non quantitative terms.
In systems engineering, dependability is a measure of a system’s availability, reliability, and its maintainability. This may also encompass mechanisms designed to increase and maintain the dependability of a system. Dependability can be broken down into three elements:
- Attributes – Awaytoassess the dependability of a system. Attributes are qualities of a system and further divided into
- Availability – readiness for correct service
- Reliability – continuity of correct service
- Safety – absence of catastrophic consequences on the user(s) and the environment
- Integrity – absence of improper system alteration
- Maintainability – ability for a process to undergo modifications and repairs
- Threats – An understanding of the things that can affect the dependability of a system. Threats are things that can affect a system and cause a drop in Dependability. There are three main terms that must be clearly understood:
- Fault: A fault (which is usually referred to as a bug for historic reasons) is a defect in a system. The presence of a fault in a system may or may not lead to a failure. For instance, although a system may contain a fault, its input and state conditions may never cause this fault to be executed so that an error occurs; and thus that particular fault never exhibits as a failure.
- Error: An error is a discrepancy between the intended behaviour of a system and its actual behaviour inside the system boundary. Errors occur at runtime when some part of the system enters an unexpected state due to the activation of a fault. Since errors are generated from invalid states they are hard to observe without special mechanisms, such as debuggers or debug output to logs.
- Failure: A failure is an instance in time when a system displays behaviour that is contrary to its specification. An error may not necessarily cause a failure, for instance an exception may be thrown by a system but this may be caught and handled using fault tolerance techniques so the overall operation of the system will conform to the specification.
- Means – Ways to increase a system’s dependability
Since the mechanism of a Fault-Error-Chain is understood it is possible to construct means to break these chains and thereby increase the dependability of a system. Four means have been identified so far:
Fault Prevention deals with preventing faults being incorporated into a system. This can be accomplished by use of development methodologies and good implementation techniques. Fault Removal can be sub-divided into two sub-categories: Removal During Development and Removal During Use. Removal during development requires verification so that faults can be detected and removed before a system is put into production. Once systems have been put into production a system is needed to record failures and remove them via a maintenance cycle. Fault Forecasting predicts likely faults so that they can be removed or their effects can be circumvented. Fault Tolerance deals with putting mechanisms in place that will allow a system to still deliver the required service in the presence of faults, although that service may be at a degraded level. Dependability means are intended to reduce the number of failures presented to the user of a system. Failures are traditionally recorded over time and it is useful to understand how their frequency is measured so that the effectiveness of means can be assessed.
ISO 9000 definition:
“Ability to trace the history, application or location of that which is under consideration.”
NOTE 1 When considering product, traceability can relate to:
- the origin of materials and parts,
- the processing history, and
- the distribution and location of the product after delivery.
Traceability is the ability to verify the history, location, or application of an item by means of documented recorded identification. Other common definitions include to capability (and implementation) of keeping track of a given set or type of information to a given degree, or the ability to chronologically interrelate uniquely identifiable entities in a way that is verifiable. Traceability is the ability to identify and trace the history, distribution, location, and application of products, parts, and materials. Traceability system records and follows the trail as products, parts, and materials come from suppliers and are processed and ultimately distributed as end products.The term “measurement traceability” is used to refer to an unbroken chain of comparisons relating an instrument’s measurements to a known standard. Calibration to a traceable standard can be used to determine an instrument’s bias, precision, and accuracy.In logistics, traceability refers to the capability for tracing goods along the distribution chain on a batch number or series number basis. Traceability is an important aspect for example in the automotive industry, where it makes recalls possible, or in the food industry where it contributes to food safety.In materials, traceability refers to the capability to associate a finished part with destructive test results performed on material from the same ingot with the same heat treatment, or to associate a finished part with results of a test performed on a sample from the same melt identified by the unique lot number of the material. Destructive tests typically include chemical composition and mechanical strength tests. A heat number is usually marked on the part or raw material which identifies the ingot it came from, and a lot number may identify the group of parts that experienced the same heat treatment (i.e., were in the same oven at the same time). Material traceability is important to the aerospace, nuclear, and process industry because they frequently make use of high strength materials that look identical to commercial low strength versions. In these industries, a part made of the wrong material is called “counterfeit,” even if the substitution was accidental.In the supply chain, traceability is more of an ethical or environmental issue. Environmentally friendly retailers may choose to make information regarding their supply chain freely available to customers, illustrating the fact that the products they sell are manufactured in factories with safe working conditions, by workers that earn a fair wage, using methods that do not damage the environment.
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