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



Each concept-except the one designed by the title of the first domain-has at least an ascendant relation and rarely more than four. As already mentioned, one and only one of the ascendant relations has to be chosen as the concept priority relation, which allows its insertion in the taxonomic tree-like structure of the thesaurus.

While a multilingual thesaurus based on a standardized terminology has been developed, the introducing of the semantic relations of a concept tries to suggest the source definition (if any) or the meaning of the source context (for not explicitly defined concepts) by using all the available source languages (three in the case of the IEC thesaurus). Our experience shows some specific aspects:

  1. The definitions are often too particular (i.e. conceived merely for the narrow application area of the chosen source publication), they are different from one source to another (if more sources are available) and they sometimes have different meanings in the different languages of the same source. These difficulties are less apparent in the last edition of the IEV, which is a highly structured vocabulary, but are inherent when many years separate the various successive chapters, for the technical progress is too fast. In consequence, a thesaurus has to integrate the source information on a larger time interval, and has to give a less restrictive semantic vicinity than a definition does.

  2. The selection of the ascendant relations has to follow a lot of rules, but cannot be done according to a precise algorithm. This selection is essentially pragmatic and guided by the interest to obtain a suggestive result with a lesser number of ascendant relations. It is rarely unique and will change according to the development of the available concept fund.

  3. The number of necessary types of basic hierarchical relations is much greater than five. For instance, all the special cases of applications of the vague RL relation (see §3.2.1.5) are distinct and very precise relations and might have been treated as independent types. The choice of only five basic relations is pragmatic and, therefore, not unique.

  4. Not all concepts have to be treated similarly. A minority of high-level concepts, the "zones" - top concepts of the chosen semantic fields - and some of their 1...3-degree descendants, are important and their ascendant relations have to suggest their definitions. Such concepts also have a rich semantic first-order descending, that completes in a very efficient manner their semantic vicinity (Table 2).

  5. The semantic vicinities may be verified by considering tree-like lists of descendant concepts on many levels (see §4.3.2). Such lists have to exclude "vicious circles" obtained from a chain of relations of the same type (homogeneous chain) and have to avoid such circular heterogeneous chains (obtained with different types of relations). The presence of DO relations can generate such chains, logically correct: the mechanical work is a form of energy transfer but the energy is defined by using the mechanical work as an originating concept.


4. Proposed lexical structures

4.1. Term category

The lexical structure of the thesaurus, language-dependent, is defined at first by relating each term of that language to its corresponding concept, language- independent. This term-to-concept relation is expressed by a term property called term category, which indicates its "level of use" in this language:

Term category Symbol Graphic reference
1. Descriptor (recommended term) @ .
2. Accepted synonym T => descriptor
3. Not recommended, obsolete term N != descriptor
4. Recommended abbreviation A .= descriptor
5. Recommended literal symbol L L= descriptor
6. Alternate, shortened or permuted, form* S -> descriptor

* With a unilateral reference to the descriptor.

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