Frequently Asked Questions on the VIM Edition 3 (VIM3) :
Q1. Why is the title of VIM Edition 3 different from the titles of VIM Edition 1 and VIM Edition 2?
The title of the VIM Edition 3 (VIM3), "International vocabulary of metrology Basic and general concepts and associated terms (VIM)", was changed from the title of the first and second editions of the VIM, "International vocabulary of basic and general terms in metrology", in order to emphasize that a vocabulary is really more than a collection of terms, and is actually a collection of definitions that express concepts (in the case of the VIM, concepts pertaining to metrology), along with the commonly used terms that designate those concepts. Further, the concepts in the VIM Edition 3 are intended to form a concept system, wherein the concepts are, for the most part, not independent, but, rather, they are related to each other.
It is sometimes the case that, in general usage, more than one term is commonly used to designate a concept. It is more frequently the case that, in general usage, more than one concept is commonly designated by a single term. This causes difficulty when developing a vocabulary, since in order to minimize ambiguity and confusion it is most desirable to use a single term to designate a single concept. In the VIM Edition 3 a single concept is always designated by what is considered to be the preferred single term (and its synonyms) used with that concept. It must be kept in mind that sometimes other terms are used in some metrology communities for the same single concept.
In practice, definitions in the VIM Edition 3 can be read, understood and used without being aware of the underlying concept system on which it is founded.
Q2. What is the difference between the use of single quotes and double quotes in the English text of the VIM Edition 3?
The VIM Edition 3 uses in the English text the convention in which single quotes ('...') surround a concept designation to indicate that the concept is
being considered and double quotes ("...") to indicate that the content is a term or a quotation; e.g. "... 'quantity' is defined as
In French, there exists only one type of quotes (« ... »), so this distinction is not made.
In the English text of these FAQs, only the double quotes are used for sake of simplification.
Q3. Why are some terms in the VIM Edition 3 in bold?
The VIM Edition 3 uses the ISO 10241:1992 convention in which the preferred term for the concept is in boldface while the synonyms are not.
In the text of a definition, its notes and examples, terms designating concepts defined elsewhere in the VIM Edition 3 are also in boldface at first mention.
For instance, in the definition of "quantity dimension" or "dimension of a quantity" or "dimension", the preferred term "quantity dimension" is in boldface, and "quantity", "base quantities", and "system of quantities" are also in boldface in the definition.
Q4. Why does the VIM Edition 3 use the term "true value" when the GUM discourages use of the word "true," considering it to be redundant?
The use of the term "true value" has become a source of confusion over the last several years, primarily because the GUM, in some places, discourages use of the word "true" in the term "true value" (e.g., see GUM D.3.5). This has led many people to believe that the GUM deprecates the concept of true value, which is not the case at all. In fact, the GUM uses the term and definition of true value as given in the VIM Edition 2 ("value consistent with the definition of a given particular quantity"), which is essentially identical to the definition given in the VIM Edition 3 ("quantity value consistent with the definition of a quantity"). However, the GUM takes the additional step of calling the concept of true value just "value", because it considers the word "true" to be redundant and therefore unnecessary.
In the VIM Edition 3 the term "true value" is kept because the word "value" already has a more general meaning, just as it did in VIM Edition 2. It is in fact confusing and unacceptable, from a vocabulary perspective, to use the same term ("value") two different ways, in both the general sense and the true value sense, and so the VIM Edition 3 does not do so. Further, the VIM Edition 3 makes the distinction between "true value" and "measured value", while the GUM instead uses the term "estimate" instead of "measured value." The VIM Edition 3 takes the approach that the terms "true value" and "measured value" are more readily self-evident and generally understood than "value" and "estimate" for their respective concepts.
Consistency between the GUM and the VIM is being pursued for the future.
Q5. Is "definitional uncertainty" actually a "measurement uncertainty"?
According to the GUM, "The first step in making a measurement is to specify the measurand the quantity to be measured; the measurand cannot be specified by a value but only by a description of a quantity. However,
in principle, a measurand cannot be completely described without an infinite amount of information. Thus, to the extent that it leaves room for
interpretation, incomplete definition of the measurand introduces into the uncertainty of the result of a measurement a component of uncertainty that may or may not be significant relative to the accuracy required of the measurement." The GUM refers to this component of uncertainty as "intrinsic" uncertainty.
In the VIM Edition 3 a more descriptive term is used for this concept ("definitional uncertainty"), defined as "component of measurement uncertainty resulting from the finite amount of detail in the definition of a measurand."
Q6. What is the difference between a quantity and a quantity value?
A quantity is a property of something, for example, the length of a particular table.
A quantity value (for example, 1.23 m) represents the magnitude of a quantity, by comparing the quantity (e.g., the length of a particular table) to another quantity (a reference quantity, such as the measurement unit metre).
This does not apply to ordinal quantities, which do not have measurement units.
Note that many quantities can have the same quantity value (for example, the values of the lengths of two or more different tables can all be 1 m).
Q7. Why are commas used in English and semicolons used in French to separate numbers in intervals?
Note 2 of 7.3.2 Decimal sign in the standard ISO 80000-1:2009 states:
NOTE 2. The General Conference on Weights and Measures (Conférence Générale des Poids et Mesures) at its meeting in 2003 passed unanimously the following resolution:
"The decimal marker shall be either a point on the line or a comma on the line."
In practice, the choice between these alternatives depends on customary use in the language concerned.
It is customary to use the decimal point in most documents written in the English language, and the decimal comma in documents written in the French language (and a number of other European languages), except in some technical areas where the decimal comma is always used.
As in French and a number of other European languages (e.g. German, Spanish, Italian, Portuguese, among many others) the usual decimal sign is a comma on the line, the semicolon is clearer for separating numbers within intervals, especially when numbers contain decimals.
Q8. What is a "primitive"?
The term "primitive" is used in this context to denote a concept that is so commonly used and assumed to be well understood by the intended readership of a vocabulary that it is not necessary to provide an explicit definition for it in the vocabulary. Some examples of primitives, taken from just the first entry in the VIM Edition 3, are: property, phenomenon, body, substance, magnitude, and reference.
Q9. Why is "précision de mesure" not used for "measurement precision" in the VIM Edition 3?
The term "précision" in French has been used in the past to express so many different concepts that the authors of the VIM Edition 3 preferred not to use it in order to avoid misunderstanding, and chose the term "fidélité de mesure".
In VIM2 a note in entry "accuracy of measurement" indicates that the term precision should not be used for "accuracy".
The French term "fidélité (d'un instrument de mesure)" was given in VIM2 as equivalent of the English term "repeatability (of a measuring instrument)".
Q10. Why is there no French term for "calibrator"?
There is not always equivalence between French and English terms. In VIM Edition 3, a French term equivalent to the English term "calibrator" was not proposed because in English the term "measurement standard" and its synonym "etalon" do not evoke "calibration". So it was logical to introduce the term "calibrator" in order to designate a "measurement standard" used for "calibration". In French it was not necessary because it is obvious that an "étalon" is used for calibration. The use of the word "calibrateur" in some French documents was known, but was considered as inconsistent with the French equivalent of "calibration".
However in practical life, several terms are used and we present some cases:
- The International Standard ISO 17511 "In vitro diagnostic medical devices Measurement of quantities in biological samples Metrological traceability of values assigned to calibrators and
control materials", the term "calibrator" was translated as "agents d'étalonnage".
- In the field of clinical chemistry the International Standard ISO 15189 "Medical laboratories Particular requirements for quality and competence", the term "calibrateur" in the French version is used (see § 5.6.2).
- The OIML International Recommendation OIML R 102 (E) and the International standard IEC 60942 translate the term "acoustical calibrator" by "calibreur acoustique".
- In electrical metrology, the term "calibrateur" is often used for "générateur de grandeurs électriques étalons", but we found also "générateur étalon".
"Calibrateur" is also used for material measures and in pressure and temperature metrology.
Q11. What is the substitution principle?
All definitions in a vocabulary must be written in such a way that a term used in a definition can be replaced by the corresponding definition without a loss of or change in meaning. This is called the substitution principle.
In the VIM Edition 3, terms denoting concepts that are defined elsewhere in the vocabulary and that appear in definitions are bolded. For example, the definition of validation is "verification, where the specified requirements are adequate for an intended use". Since the term "verification" is bolded in the definition, there is a definition of verification elsewhere in the
VIM Edition 3, namely "provision of objective evidence that a given item fulfils specified requirements".
The substitution principle requires that the definition of "verification" be written in such a way that it can be inserted verbatim into the definition of validation such that there is no loss of or change in meaning in the definition of validation. This can be seen by performing that operation:
"provision of objective evidence that a given item fulfils specified requirements, where the specified requirements are adequate for an intended use."
Q12. Are all definitions and notes in the VIM Edition 3 applicable to ordinal quantities?
No, they are not. Ordinal quantities do not follow the rules of quantity calculus. For example, it is not meaningful to take an average of values of ordinal quantities.
Q13. Why do we have a new definition of calibration in VIM3?
The VIM3 definition of calibration extends the previous (VIM2) definition by clarifying that a calibration involves not only comparing indications of measuring instruments with corresponding values (and uncertainties) of measurement standards, but also involves using these comparisons in an "inverse" manner, in order to be able to assign a measured value and measurement uncertainty to an item being measured by the measuring instrument, based on the indication of the measuring instrument.
Previously, the definition of calibration concerned only the first step of the VIM3 definition. However, inclusion of the second step leads to a more operational definition as it introduces the practical use of the calibration of a measuring instrument. By including both steps it is possible to demonstrate metrological traceability of the measurement results obtained using the measuring instrument after it has been calibrated.
Calibration should not be confused with verification or adjustment. Calibration is a prerequisite for verification, which provides confirmation that specified requirements (often maximum permissible errors) are met. Calibration is also a prerequisite for adjustment, which is the set of operations carried out on a measuring system such that the system provides prescribed indications corresponding to given values of quantities to be measured, typically obtained from measurement standards.