The article discusses specific features of a thesaurus and provides an overview of how a particular thesaurus is used in Hungarian practice.

Polythematic Structured Subject Heading System (PSH) has been published in a machine-readable format in a manner that adheres to the linked data design principles and best practices. This improvement opens many new ways for exploiting PSH and building upon its rich structure. These possibilities include auxiliary tools for intellectual indexing and foundations for use in automatic indexing applications. In this form PSH may be employed in the metadata standards that allow for serialization in various formats which can be easily embedded in electronic documents.

The article is based on comparison of traditional bibliographic databases used for searches concerning mainly metallurgy and related fields (METADEX and Czechoslovak database METAL) with innovative database "CSA Illustrata: Technology". Scope of periodicals abstracted and indexed in individual databases is compared, as well as results of searches based on real customer requests. Although new database brings to users many principal benefits, it is not yet suitable for the needs of metallurgists, mainly due to lack of relevant data - probably due to its rather limited retrospective. Text is supported by factual findings summarised in six tables.

The article is focused on a particular dictionary called ORBIS (non-alphabetical dictionary of the semantic classes) and on related semantic classes. It shows that the distribution of words in semantic classes is uniform, and even fullfills Zipf law (Mandelbrot law). Furthermore, it shows that the semantic classes are stable according a certain numerical criterion. It also shows that subdictionary of scientific terms in the scientific text fullfills the Mandelbrot law. Correspondence of the semantic classes with the fields of sciences and a comparison with the classification of sciences is also a part of the article.