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Grouping Constructs

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.

Proposals:

Grouping in Thesauri

ISO 2788-1986

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

BS 8723-2:2005

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]."

See also the glossary at http://www.willpowerinfo.co.uk/glossary.htm - this is published by one of the editors of [BS 8723-2:2005] and should therefore be consistent with it.

[AlistairMiles: Beware! The use of the word "facet" is not necessarily consistent between [ISO 2788-1986] and [BS 8723-2:2005].]

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
    ...

However, other uses of guide terms in the AAT do not correspond obviously to anything mandated in either [ISO 2788-1986] or [BS 8723-2:2005]. For example: 

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.

References