This page provides some background and discussion relating to various types of grouping constructs found in some thesauri, and also in other types of concept scheme. This page relates to ISSUE-33: GroupingConstructs.
/ProposalOne - "Minimal Fix"
/ProposalTwo - "Bundles"
/ProposalThree - "Loosening domains and ranges"
Grouping in Thesauri
Section 9.3.3 of [ISO 2788-1986] discusses the use of node labels in thesauri. It states: "Two kinds of node label, each with a different function, may be inserted into the schedules of a systematic thesaurus...".
The first kind of node label is that which "... serve[s] as a facet indicator to show the logical basis on which the hierarchy was organised...". The example given is as follows:
AIRCRAFT By payload FREIGHT AIRCRAFT PASSENGER AIRCRAFT By user CIVIL AIRCRAFT MILITARY AIRCRAFT
[ISO 2788-1986] further states: "In this example, By payload and By user function as node labels. They introduce terms that are narrower than the class [SIC] preceding the node label."
In other words, the alphabetic display of the same example would show the following:
AIRCRAFT NT FREIGHT AIRCRAFT NT PASSENGER AIRCRAFT NT CIVIL AIRCRAFT NT MILITARY AIRCRAFT
The second kind of node label is that which is "... used to introduce different types of concepts [SIC], ensuring that these are collocated, for the convenience of the user, under the concept(s) with which they are usually associated." The example given is as follows:
BOOKS Operations BINDING PRINTING
Note especially that the node label "... serves only to collocate associated concepts ..." - not broader/narrower.
In other words, the alphabetic display of the same example should show the following:
BOOKS RT BINDING RT PRINTING
Section 9 of [BS 8723-2:2005] follows similar (if not identical?) principles for the use of node labels in thesauri.
The following example is given to illustrate use of node labels to give the "characteristic of division" by which a concept is subdivided into an "array" of narrower concepts:
electromagnetic radiation <by wavelength> ultraviolet radiation visible radiation infrared radiation microwave radiation radio waves
Note that, in this example, the narrower terms have been arranged systematically and not alphabetically. [BS 8723-2:2005] states: "The terms in an array may be arranged either alphabetically or systematically. Alphabetical sequence should be used when there is no other obvious way to arrange a group of concepts. Systematic sequence should be used when it is likely to be familiar to most users, or when the arrangement helps to clarify the scope of the terms. In the example for electromagnetic radiation, the types of radiation are presented in order of increasing wavelength, as this might help some indexers in selecting the correct term(s). "
The above usage of node labels is the same as the first kind of usage allowed in [ISO 2788-1986].
[BS 8723-2:2005] also allows the use of node labels to introduce "facets". For example:
agricultural industries (people) farm managers dairy personnel shepherds (products) cereal products dairy products
This is similar (if not identical?) to the second kind of usage allowed in [ISO 2788-1986]. Note especially that: "... where the label introduces a new facet, the terms that follow are typically not narrower terms of the preceding term: farm managers and cereal products, etc., are not narrower terms of agricultural industries ...". Unfortunately, [BS 8723-2:2005] does not indicate whether the following alphabetical display would be correct for the example shown above:
agricultural industries RT farm managers RT dairy personnel RT shepherds RT cereal products RT dairy products
Note finally that [BS 8723-2:2005] states: "Node labels are not preferred terms or non-preferred terms. They are present only for the purposes of systematic display, and they do not qualify for any of the inter-term relationships described in Clause 8 [I.e. broader, narrower, related, use, used for]."
The Art and Architecture Thesaurus (AAT)
The AAT has the notion of a guide term.
Some uses of guide terms obviously correspond to the use of node labels to introduce a characteristic of division as described in [ISO 2788-1986] and [BS 8723-2:2005], for example (guide term shown within angle brackets):
chairs <chairs by form> armchairs ax chairs backstools ...
Styles and Periods <styles and periods by region> <The Islamic World> Saracenic pre-Islamic <Islamic World dynastic styles and periods> Orthodox Caliphate Umayyad Abbasid
Grouping in Tagging Systems
Some tagging systems such as http://del.icio.us allow users to group tags into "bundles". Note that bundles cannot be used as tags.
[ISO 2788-1986] Documentation - Guidelines for the Establishment and Development of Monolingual Thesauri, ISO 2788-1986
[BS 8723-2:2005] Structured vocabularies for information retrieval — Guide — Part 2: Thesauri, BS 8723-2:2005