Alexandru Timotin, Florin Teodor Tãnãsescu * Structures for a Thesaurus of Technical Terminology



3.2.1. Hierarchical relations

Hierarchical relations are asymmetrical and can be ascendant or descendant. Each ascendant relation (with symbol < ) has a unique inverse, the related descendant relation (with symbol > ) and reciprocally.

A hierarchical relation should be immediate in the given concept fund, i.e. it should attach a concept to its nearest concept of this concept fund and according to the relation viewpoint. A relation can be logical when it refers to the concept features, and factual when concerned with the concept designated elements.

Only the ascendant relations will be presented in the following examples. The descendant ones result by inversion. The concept types will be put between brackets [...]. The parts of the terms put between parentheses are often omitted. The terms may be followed by a complement put between brackets: a comment requested, e.g. for the separation of homonyms.

1).The specific relation SG (< G) with the inverse GS ( > S)

specific concept < G generic concept <-> generic concept > S specific concept

This relation represents the strictly logical subordination. The set of the elements designated by the specific concept must be a proper sub-set of the set of elements designated by the generic concept. The generic concept has to be a proximate one, in the available concept fund. Consequently this is not a transitive relation and, therefore not an order one. The two concepts have to be of the same type or of compatible types. Examples:

speciestype genus proximustype
(electric) power line [P] < G electric line [P]
electric field strength [Q] < G polar vector Q]
ion [F] < G charged particle [F]
material [M] < G (fabricated) product [P]
component [C] < G (fabricated) product [P]
signal [T] < G physical phenomenon [F]

Improper use of the SG relation: incompatible types

Ward-Leonard set [P] < G electric drive [T]
ideal dipole [theoretic model] [G] < G electric dipole [physical object] [F]

Improper use of the SG relation: the generic concept is too far (not proximate)

speed [Q] < G measurable quantity [Q]

2). The attributive relation QE (< E) with the inverse EQ ( > Q)

property / feature < E entity <-> entity > Q property / feature

This relation is also a logical one, the old Aristotelian "attribution" attaching a quality to a characterized "substance" or entity (an object or a process). The first concept should be of the Q type and the second one of a non-Q type. Consequently, it is not a transitive relation and, therefore, not an order one. Typical models:

featuretype entitytype
a) quality, property [Q] < E [#Q]
colour [Q] < E Visible radiation [F]
form [Q] < E Geometrical figure [G]
b) set of properties [Q] < E [#Q]
state [Q] < E System [P]
thermal equilibrium [Q] < E Thermodynamic system [F]
c) measurable quantity [Q] < E [#Q]
area [Q] < E Surface [G]
energy [Q] < E Physical system [F]
efficiency [Q] < E Machine [P]

Remarks:

  1. A feature of a Q-type concept (that is, a "feature of a feature") is a second (or higher) order "attribution" and has not to be treated as a QE relation, that requires a non-Q-type second member. The vague RL relation has to be used instead. For instance a colour may be more or less dark, therefore one can put
    darkness [Q] < L colour [Q], but not
    darkness [Q] < E colour [Q]
  2. From the grammatical point of view the first concept (the property) may be: noun, adjective, adverb.

  3. One can recognize two kinds of properties: intrinsic or definitional (entering the definition of the concept, i.e. of the second member entity) and extrinsic (not implied in this definition). In the first case it is preferable to avoid the QE relation and use instead an OD one. Example: instead of
    electric < E electric machine, one can put
    electric > D electric machine i.e. electric machine < O electric


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