Role of terminology
in scientific and technical communication

What follows, authored by Luca Mari with assistance from Joanna Goodwin, provides a general introduction to the role of terminology in scientific and technical communication, and particularly to definitions, a critical component of standards documents. Parts of the text have been taken from L. Mari, Evolution of 30 years of the International Vocabulary of Metrology (VIM), Metrologia, 52, R1-R10, 2015, doi:10.1088/0026- 1394/52/1/R1.


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Science, communication, and language

Science is a social endeavour and therefore an important task for it is communication, as enabled by language.


The language par excellence for empirical sciences is mathematics, but mathematical statements become meaningful expressions of empirical sciences only because they are properly interpreted (consider the difference between X=YZ and F=ma), i.e., they are parts of a mathematical model, a structure providing a nomological network connecting mathematical constructs interpreted as non-mathematical concepts (such as force, mass, and acceleration). This is a matter of domain theories, paradigmatically physics, which justify such interpretations on empirical grounds.


Hence mathematics is advantageous (and some would claim necessary) in empirical sciences, but is not the whole story. Even though it is possible to present a mathematical subject in purely mathematical language (i.e., using only formulae, and no natural language), some pieces of communication in non-mathematical language are required to convey information on non-mathematical topics (e.g., «let F be force»).


This raises a delicate issue: how can we prevent, or at least minimize, the ambiguities of natural languages from corrupting the precision of mathematics? As we will see, definitions play a critical role in the solution to this problem.

Functions of language: Shannon and Jakobson models

Language has many functions, for example to exhort someone to do something or to express feelings or emotions. A basis for identifying and understanding such functions is the model adopted by C. Shannon in his mathematical theory of communication, presenting the simplified situation of two communicants, a source and a destination, where «the fundamental problem of communication is that of reproducing at one point either exactly or approximately a message selected at another point» [Shannon 1948].


Source: [Shannon 1948].


A more sophisticated and encompassing model was proposed in linguistics by R. Jakobson [Jakobson 1960], based on factors of communication and functions of communication.


According to Jakobson six factors are generally relevant to a communication act:

  • the addresser: the author or speaker;
  • the addressee: the reader or listener;
  • the context: entities, events, and circumstances in the outside world;
  • the contact: the channel of communication between the addresser and the addressee;
  • the code: the language in which the message is expressed;
  • the message: the utterance or text itself.

Depending on its aims, a communication act focuses on one or more of such factors, and correspondingly assumes a specific function. By taking the factors into account one by one, the following functions are identified:

  • the emotive function, that focuses on the addresser by expressing some feeling or belief (e.g., «Ouch!»); its aim is expressive;
  • the conative function, that focuses on the addressee by attempting to produce a particular reaction (e.g., «Drink!»); its aim is persuasive (or imperative);
  • the referential function, that focuses on the context by referring to things outside the communication act itself (e.g., «It is raining.»); its aim is informative (or descriptive, or explanatory);
  • the phatic function, that focuses on the contact by referring to or intending to effect the communication between the addresser and the addressee (e.g., «Are you there?»); its aim is metacommunicational;
  • the metalinguistic function, that focuses on the code by referring to the language, or other code, in which the message is expressed (e.g., «No means no.»); its aim is informative;
  • the poetic function, that focuses on the message by calling attention to its own form (e.g., «How now, brown cow?»); its aim is aesthetic.


In real life communication, seldom do these functions appear alone. To take one of Jakobson’s examples, the political slogan «I like Ike» clearly expresses a sentiment of the addresser (emotive function); it also calls attention to itself through the repeated vowel sound (poetic function); finally, and a little less obviously, because it was a campaign slogan, it was intended to encourage the addressee to like Ike (conative function).

The Jakobson model and scientific and technical communication

Not all functions identified in the Jakobson model are relevant to scientific and technical communication, which is constructed in particular around questions, proposals, rules, and sentences [Bunge 1967: p.10]. The referential function predominates, or should predominate, in most informative writing, complemented by the phatic function (in section titles, indexes, etc) and the metalinguistic function (in definitions).


In particular, definitions are critical means to set the linguistic context in which any subsequent communication can be proficiently performed. Hence, the understanding of their structure and role is useful.

Definitions as knowledge tools: terms, concepts, objects

Definitions are everyday communication tools in scientific and technical publications, but what a definition is and the role of definitions in knowledge construction and communication are usually subjects that are overlooked.


Firstly, it is «useful for our purposes to distinguish between concepts [...] and the corresponding terms, the verbal or symbolic expressions that stand for those concepts» [Hempel 1966: 275] (hence a term is not constrained to be a single word: “measurement uncertainty” is one term), where concepts are «units of knowledge» [ISO 1087-1:2000: 3.2.1], that in order to be communicated, stored, processed, etc indeed require a linguistic form.


Definitions are tools involving relations between language, knowledge, and the world:

  • knowledge is aimed at being knowledge of entities of the world: for example, the concept ‘measurement’ is intended to be about actual measurement processes;
  • knowledge is managed by means of linguistic expressions: the concept ‘measurement’ is written “measurement” in English and “mesurage” in French;
  • if knowledge is properly established and shared, then both the English “measurement” and the French “mesurage” designate actual measurement processes.

The relations between language, knowledge, and the world, and more specifically between terms, concepts, and entities in the world, are effectively depicted in the so-called “triangle of reference”, or “semiotic triangle” [Ogden, Richards 1923].


The semiotic triangle, in the general case (left) and the specific case (middle), with an example (right). Adapted from [Ogden, Richards 1923: p.11].


This model is so fundamental that, perhaps not so amazingly, the related terminology is not standardized. For example, instead of «term, concept, entity of the world», [Ogden, Richards 1923] use «word, thought, thing», and [Bunge 1974: p.XI] uses «symbol, construct, fact», whereas [ISO 1087-1:2000] uses «designation, concept, object».

Terms, concepts, objects: a notational convention

A term usually stands for the object it designates, but sometimes we use terms to refer to concepts or even to terms themselves. For example, on the subject of measurement one could write that it is a process aimed at producing quantitative information: here the reference is to the object-measurement, a process performed by means of suitable instruments etc. On another hand, one could write that measurement is intended differently in physical and social sciences: here the reference is to the concept-measurement, a critical unit of knowledge in metrology. Finally, it might be even the case that one wants to emphasize that measurement is an English noun, the plural form of which is measurements: here the reference is to the term-measurement, a lexical entity


In order to maintain a clear distinction between terms referring to objects, concepts, and terms, we adopt hereinafter a notational convention from ISO standards, e.g., [ISO 704:2009]. A term, and more generally a linguistic expression, referring to:

  • itself, i.e., a term, is delimited by double quotes;
  • a concept, i.e., its meaning, is delimited by single quotes;
  • an object, i.e., its referent, is not delimited.

Hence, (the concept) ‘measurement’ is expressed in English by (the term) “measurement” and is about (the object) measurement. The lack of delimiters around terms for objects (i.e., entities of the world) follows an economic principle: in everyday writing, we usually intend to refer to objects, and not to concepts or terms. To maintain a consistent notation, quotations are delimited herein using guillemets «as in this example».

The complex relations between terms and concepts: synonymy and homonymy

While one might hope that terms, concepts, and objects are related by unequivocal relations, this is generally, and unfortunately, not the case.


It may happen that two or more terms are used to designate the same concept, such terms being called synonyms («synonymy is the relation between differing designations that designate the same concept» [ISO 704:2009: 7.2.4]). Synonyms can be easily recognizable lexical variations (e.g., “dimension of a quantity” and “quantity dimension” [IEV 112-01-11]), but this is not always the case, so that for example “quantity of dimension one” and “dimensionless quantity” are defined as synonyms [IEV 112-01-13] even though this relation is not obvious at all from their lexical structure.


In technical standards, whenever a concept is designated by more than one term, one of them is established as the preferred term, i.e., the one recommended by the authors of the standard, while the remaining ones are admitted terms or deprecated terms [ISO 704:2009: 7.2.6] (information regarding the choice or formation of terms for concepts might be the subject of a future paper).


Synonymy is a form of redundancy, not really harmful for mutual understanding. More critical is instead the situation in which the same term designates two or more distinct concepts, such concepts being called homonyms («homonymy arises when two or more concepts have identical designations» [ISO 704:2009: 7.2.3]). Homonymy is a basic cause of ambiguity («I mean x but you understand y») and, while usual in natural language communication, it is generally to be avoided in technical standards. From this perspective, the International Electrotechnical Vocabulary (IEV) [IEC 60050] is of particular interest since it comprises an organized collection of terms and definitions from the IEC fields of technical activity: the presence of homonyms in it is the sign that in different sub-fields of electrotechnology, the same term is used indeed with different meanings.

What is defined: types of definition

A frequent source of confusion is whether what is defined are concepts or terms. In fact, «definitions are offered for one or the other of two quite different purposes: [one is] to assign, by stipulation, a special meaning to a given term which may be a newly coined verbal or symbolic expression (such as “pi-meson”) or an old term that is to be used in a specific technical sense (e.g., the term “strangeness” as used in the theory of elementary particles). [These definitions] will be called stipulative. [The second possible purpose for a definition is] to state or describe the accepted meaning, or meanings, of a term already in use. [These definitions] will be called descriptive.» [Hempel 1966: 275].


The two cases share the same abstract pattern:

defined entity := defining entity


but differ in what the involved entities are.


Stipulative definitions: defining terms

Stipulative definitions «serve to introduce an expression that is used in some specific sense in the context of a discussion, or a theory, or the like», and therefore «what they actually define are the terms that label the given units of knowledge» [Hempel 1966: 276].


A stipulative definition is then intended as a tool to introduce a linguistic equivalence, typically in the form of a shortcut. In the simplest case, a stipulative definition enables a purely lexical substitution (let “average(x,y)” be a substitute of “(x+y)/2”), where then both the defined entity and the defining entity are terms, and in principle the knowledge of the meaning of the defining term is not required to use proficiently the definition. The pattern of a stipulative lexical definition is then:

defined term := defining term


A stipulative definition may also establish an association of a previous unnamed concept to a previously nonexisting term aimed at designating the concept (e.g., “standard time” defined as ‘time scale derived from coordinated universal time, UTC, by a time shift established in a given location by the competent authority’ [IEV 113-01-17]). Also in this case what is actually defined is the new term, whereas the defining concept is supposed to be understood before and independently of the definition. The pattern of a stipulative conceptual definition is then:

defined term := defining concept


In a stipulative definition, provided that the defining entity is actually understood, the objection «I do not understand the definition» does not apply, and «I do not agree with the definition» can only mean ‘I would have chosen a different term for this concept’.


A stipulative definition can be wrong (e.g., “average(x)” defined as “(x+y)/2”), but it is conventional, and as such neither true nor false.

Descriptive definitions: defining concepts

Descriptive definitions «purport to analyze the accepted meaning of a term and to describe it with the help of other terms, whose meaning must be antecedently understood if the definition is to serve its purpose [, so that] they may be said to be more or less accurate, and even true or false» [Hempel 1966: 276].


A descriptive definition does not introduce a new term, but associates a concept, that is supposed to be understood before and independently of the definition, to an already used term, that is thus supposed to have an at least implicit meaning. Hence the definition is a means to clarify or specify this meaning, or possibly just to make it explicit.


According to [ISO 1087-1:2000: 3.3.1] a definition is indeed a «representation of a concept by a descriptive statement which serves to differentiate it from related concepts». The pattern of a descriptive definition is then:

defined concept := defining concept


where, of course, the defined concept is designated in the definition by a term (or two or more terms, then contextually defined as synonyms).


For example, a definition written as «measurement: process of experimentally obtaining one or more values that can reasonably be attributed to a quantity» [IEV 112-04-01] is a sophisticated conceptual structure whose user is expected:

  • to have at least a generic previous knowledge of the meaning of the term “measurement”;
  • to understand the meaning conveyed by the expression “process of experimentally obtaining one or more values that can reasonably be attributed to a quantity”;

so that the definition specifies the meaning of “measurement”, i.e., the concept ‘measurement’, through the meaning of the expression “process of experimentally obtaining ...”.


The pattern of a descriptive definition is in principle independent of the language in which the definition is written, so that one could assume that, e.g., the French version of the above definition, «mesurage: processus consistant à obtenir expérimentalement une ou plusieurs valeurs que l’on peut raisonnablement attribuer à une grandeur» conveys exactly the same meaning, and therefore defines exactly the same concept, as the English version, despite the fact that different terms are used. Whether this is actually the case is a matter of exactness of translation, where the possibility of completely exact translations between natural languages is a debated issue (see the note “Linguistic relativity”).


In a descriptive definition, provided that the defining concept is actually understood, the objection «I do not understand the definition» might be intended as ‘I do not understand how the defining concept relates to what I know of the defined concept’, and «I do not agree with the definition» could mean ‘what I know of the defined concept is not compatible with the defining concept’. A descriptive definition that aims at reflecting the meaning that a given community attributes to the defined concept can then be true or false, where acceptance by the community operates as the criterion of truth.


Descriptive definitions connect concepts, and as such are the building blocks of concept systems.

Definitions as tools for building concept systems

A descriptive definition is a tool that produces knowledge by connecting concepts, i.e., the upper vertices of semiotic triangles, in such a way that the defined concept X is assumed to be equivalent to the defining concept Y, which is usually constituted of a sequence of concepts Y1, ..., Yn. This relation is supposed to establish conditions that are:

  • individually necessary: each defining concept Yi is required to define X, so that removing one or more defining concepts would not define X but a more generic concept;
  • conjointly sufficient: all defining concepts Y1, ..., Yn together define X, and not a more specific concept.

On this basis, the structure of descriptive definitions is explicitly recursive: the concept X is defined by means of the concepts Yi. This makes the construction of a concept system a critical process: how can an infinite regress be avoided? To address this issue, three structural strategies can in principle be envisioned: cross-definition, bottom-up, and top-down

Strategies for building concept systems: cross-definition

One structural strategy for building a concept system is cross-definition: concepts are directly or indirectly defined in reference to one another, and then the system grows from a bootstrap effect. This is the only option if all concepts in the system must be defined, a situation that is usually deemed as unavoidable in dictionaries of natural languages and allows their loose structure, but that is tentatively avoided in scientific and technical communication, where a more formal structure is expected.

Strategies for building concept systems: bottom-up, i.e., extensional definitions

Another structural strategy for building a concept system is bottom-up: concepts referring to individual entities of the world are defined by means of some kind of direct reference («‘kilogram’ is defined as the mass of that object», uttered while indicating a given object, maintained in Sèvres), and then other concepts are obtained by means of extensional definitions [ISO 1087-1:2000: 3.3.3], that list the possible cases of the concept under definition according to a disjunctive logic:

X := y1 or ... or yn


where the set {yi} of the defining entities is called the extension of the defined concept X (for a different kind of extensional definition, see the note “Recursive definitions”).


In this case, the specifics define the generic (the example of an extensional definition for ‘base quantity in the International System of Quantities’ might be ‘length, mass, time, electric current, thermodynamic temperature, amount of substance, luminous intensity’, provided that ‘length’, ‘mass’, etc have already been defined in some way; hence the quantities length, mass, etc are the elements of the extension of ‘base quantity in the International System of Quantities’).


This strategy is attractive for its limited theoretical burden, which gives it an empiricist flavour, but is applicable only within finite domains in which it is possible to create explicit listings of all cases of a concept.


Strategies for building concept systems: top-down, i.e., intensional definitions

A third structural strategy for building a concept system is top-down: some generic concepts are assumed without a definition – they are called “primitive concepts” or simply “primitives” – and other concepts are subsequently derived from them according to a conjunctive logic:

X := Y1 and ... and Yn


where the set {Yi} of the defining concepts is called the intension of the defined concept X.


In this case, the generics define the specific. For example, the definition of ‘measurement’, ‘process of experimentally obtaining one or more values that can reasonably be attributed to a quantity’ [IEV 112-04-01], can be understood as a nice rephrasing of: measurement (X) is a process (Y1) and (the process) is an experimental obtainment of values (Y2) and is a reasonable attribution of (these) values to a quantity (Y3). Evidently, for such a definition to be well formulated the defining concepts (‘process’, ‘experimental obtainment of values’, ‘reasonable attribution of values to a quantity’) must be previously defined.


This shows that the selection of the primitives for a concept system is a critical decision: they should be simple enough to be unambiguously understood by everyone or, in the case of a domain-related concept system, they should be extra-domain, under the assumption that all domain-relevant concepts are instead defined in the concept system.


In a concept system built according to this top-down strategy, definitions are specification means: through definitions the system is built by progressive knowledge specification, where the relation between the defined concept X and each of the defining concepts Yi is then species-genus, i.e., subtype-supertype, or, according to the ISO standards on terminology work, subordinate-superordinate (hence in the definition mentioned above ‘measurement’ is a species / subtype / subordinate of the genus / supertype / superordinate ‘process’).


Furthermore, concept systems are appropriately structured top-down through intensional definitions [ISO 1087-1:2000: 3.3.2], in which one defining concept Y1 is singled out as the superordinate, with the remaining Y2, ..., Yn being its delimiting characteristics [ISO 1087-1:2000: 3.2.7]. This leads to the template:

defined concept := superordinate concept such that delimiting characteristics


that can be read

X is a Y1 such that Y2 and ... and Yn


(i.e., a measurement (X) is a process (Y1) such that it is an experimental obtainment of values (Y2) and is a reasonable attribution of these values to a quantity (Y3)) (on the at least twofold meaning of the relation ‘is a’, see the note “On the is a relations”). Hence, «definitions shall include the superordinate concept immediately above, followed by the delimiting characteristic(s). The superordinate concept situates the concept in its proper context in the concept system.» [ISO 704:2009: 6.2]. A concept system built in compliance with this template is strictly hierarchical, with each child (subordinate) concept having only one parent (superordinate) concept, and all concepts without parents – at least one of them must be included in the system – are primitives (for a possible generalization, see the note “Non-hierarchical concept systems”).

The relation between the extension and the intension of concepts

Any pair of concepts that are in a subordinate-superordinate relation have an interesting relation in terms of their extension and intension. Let us consider the case of ‘base quantity’ and ‘quantity’, as defined by [IEV 112-01-08 and IEV 112-01-01]. Of course, a base quantity is a quantity, whereas ‘quantity’ is defined as a specific property. Hence given:

a quantity is a property such that Y2 and ... and Yn


(where Y2, ..., Yn are the delimiting characteristics in the definition of ‘quantity’), the definition of ‘base quantity’ is:

a base quantity is a quantity such that Z2 and ... and Zm


(where Z2, ..., Zm are the delimiting characteristics in the definition of ‘base quantity’), which can be written also:

a base quantity is a property such that Y2 and ... and Yn and Z2 and ... and Zm


This shows that for defining a subordinate concept it is necessary to extend the intension of the superordinate concept, by adding one or more delimiting characteristics. On the other hand, each instance of the subordinate concept is also an instance of the superordinate concept (each base quantity is a quantity) but generally not vice versa (there might be quantities that are not base quantities), so that the extension of the subordinate concept is included in the extension of the superordinate concept.


The conclusion is that subordinate-superordinate concepts are inversely related as for their intensions and extensions: when the intension is extended, the extension is correspondingly restricted, and vice versa.

Some rules for intensional definitions

Technical standards usually include intensional definitions, and therefore terminology works such as [ISO 704:2009] give rules and suggestions for the construction of intensional definitions and the choice of the terms that designate the defined concepts.


The fundamental rule derives from the definition of intensional definitions as a specification means, so that they must be specific, so as to refer only to the intended objects, but not too specific, so as to refer to all intended objects. As already mentioned above, this implies that the delimiting characteristics listed in the defining concept must be individually necessary and conjointly sufficient.


Let us consider again the case of ‘measurement’, defined as ‘process of experimentally obtaining one or 7 more values that can reasonably be attributed to a quantity’ [IEV 112-04-01], i.e., in reference to the three conditions of (Y1) being a process, (Y2) an experimental obtainment of values, and (Y3) a reasonable attribution of values to a quantity. The complementary questions are:

  • is each of them really necessary to define ‘measurement’? or vice versa, e.g., at least in some cases Y3 could be dropped and a (more generic) process of an experimental obtainment of values (where such values might then be “unreasonably attributed to a quantity”...) would still be considered a case of measurement?
  • are all of them really sufficient to define ‘measurement’? or vice versa at least in some cases are there measurements which nevertheless do not satisfy such conditions?

Furthermore, an intensional definition should:

  • establish a hierarchical relation between the defined and the defining concept (and therefore it should not be circular, as it would be if, e.g., ‘measurement’ were defined in terms of quantities and ‘quantity’ in terms of measurements);
  • be expressed in terms understandable for the intended users (and therefore it should not be obscure, as it would be if, e.g., ‘measurement model’ were defined in terms of partial differential equations (PDEs) in the case that PDEs are not expected to be known to the intended users);
  • define what the concept is, not what the concept is not (and therefore it should not be negative, as it would be if, e.g., ‘nominal property’ were defined as a property which is not a quantity).

Precising definitions

While the distinction between stipulative and descriptive definitions is in principle clear, it is not sufficient to grasp the intended role played in technical standards by many definitions, that are meant:

  • to report the actual usage of concepts employed by experts (instead of introducing brand new concepts and terms), and in this sense they are descriptive,

and at the same time

  • to prescribe a specific usage as standard (instead of just listing all observed usages), and in this sense they are stipulative.

A definition sharing these aims, that can be called a precising definition, in a sense “stands in the middle” between stipulative and descriptive definitions:

  • being descriptive, it has external criteria of validity: if nobody uses the concept as defined, it would be invalid;
  • being stipulative, it has external criteria of acceptance: if the proposing body is not acknowledged, it would not be accepted.

Writing precising definitions is the usual challenge for technical standardization bodies, and is one of the tasks to which IEC TC 1: Terminology, contributes in its overall responsibility to develop and maintain the content of the International Electrotechnical Vocabulary (IEV).


Note: Linguistic relativity

That knowledge is not completely language-invariant, and therefore that “the structure and lexicon of one’s language influences how one perceives and conceptualizes the world, and they do so in a systematic way” [Swoyer 2014], is a position called “linguistic relativity”, and sometimes the “Sapir–Whorf hypothesis”.


Note: Recursive definitions

A specific kind of extensional definitions are recursive definitions, in which the disjunctive logic:

X := y1 or ... or yn


is realized implicitly by means of a structure of the kind:

X := y1

if X := yi then also X := yi+1


i.e., one “base entity” y1 is explicitly stated as belonging to the extension of X, ext(X), and a sequencing rule for entities is given such that if an entity yi belongs to ext(X) then also the subsequent entity yi+1 belongs to ext(X).


A well-known example of a concept defined in a recursive way is ‘natural number’, as follows (after Peano):

0 is a natural number (i.e., 0 belongs to ext(natural number));

each natural number yi has a unique successor yi+1, such that:

  • the successor of a natural number is also a natural number;
  • distinct natural numbers have distinct successors;
  • no natural number is succeeded by 0

(Compare this with the definition given in the IEV, «element of the unlimited sequence {0, 1, 2, 3, ...}» [IEV 102-02-01], which is more compact with the intent of being more readily understandable, but at the cost of being less precise, as in principle it does not preclude interpretations such as, e.g., {0, 1, 2, 3, 0, 1, 2, 3, …}.)


Note: On the is a relations

The subordinate-superordinate relation expressed by “X is a Y” is the fundamental building block of a concept system, but unfortunately the relation is a has (at least) two distinct meanings, is subtype of and is instance of. Consider, for example:

  • a material measure is a measuring instrument: this means that the concept ‘material measure’ is a specification of the concept ‘measuring instrument’; this is a concept-concept relation;
  • the International Prototype of the Kilogram (IPK) is a measurement standard: this means that the object IPK is an example of the concept ‘measurement standard’, i.e., an instance of it; this is an object-concept relation.

Note: Non-hierarchical concept systems

There is nothing necessary in the single inheritance pattern assumed by intensional definitions, and in fact the alternative single vs multiple inheritance (e.g., in object-oriented programming languages Java vs C++) is an open-ended discussion. Single inheritance leads to much simpler tree-like (instead of directed graph) structures. Examples of top-down non-hierarchical definitions are ‘value of a quantity’ defined as «number and reference together expressing magnitude of a quantity» [IEV 112-01-28] and ‘metrology’ defined as «science of measurement and its application» [IEV 112-04-02]. In both definitions there is more than a single superordinate: ‘number and reference’ and ‘science and its application’ appear to be the conjunction of two concepts. This hinders specifying “a value of a quantity is a Y” and “metrology is a Y”, where Y is a single concept. The second case is easily resolved, for example by rephrasing as “body of knowledge that includes the science of measurement and its applications”, thus defining metrology as a body of knowledge. The first case is instead delicate, and the definition mentioned seems to suggest a lack of general agreement about what a value of a quantity is.



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