Controlled Vocabularies Paul Miller Interoperability Focus UKOLN P. Miller@ukoln. ac. uk http: //www. ukoln. ac. uk/ UKOLN is funded by Resource: the Council for Museums, Archives and Libraries, the Joint Information Systems Committee (JISC) of the Further and Higher Education Funding Councils, as well as by project funding from JISC and the EU. UKOLN also receives support from the Universities of Bath and Hull where staff are based. 1
Controlled vocabularies • What are they? • Why do we need them? • Where do we get them from? 2
What are they…? • Not worrying too much about the distinction between thesauri, category lists, etc. for now… • Widely agreed sets of terms describing concepts within a domain – Often backed up by definitions (scope notes) – Sometimes hierarchical – Rarely very good at linking together… – UK GPCL and GCL… 3
Hierarchies of Meaning ‘Beer Glass’ ‘White wine glass’ ‘Glass’ ‘Wine Glass’ ‘Red wine glass’ 4
Equivalence • There are often situations in which users or cataloguers wish to allow multiple synonyms for any one term. – In these cases, one term may be defined as a preferred term “Electricity Plant USE Power Station” – Here, ‘Power Station’ is the preferred term Example from RCHME Thesaurus of Monument Types, © RCHME 1995. 5
Hierarchy • An important capability of thesauri is their ability to reflect hierarchies, whether conceptual, spatial, or whatever. – Individual thesaurus entries are linked to a class (CL), as well as to broader (BT) and narrower (NT) terms. “BAYONET CL Armour and Weapons BT Edged Weapon NT Plug Bayonet NT Socket Bayonet” Example from mda Archaeological Objects Thesaurus, © mda, English Heritage, RCHME 1997. 6
Association • In any large thesaurus, a significant number of terms will mean similar things or cover related areas, without necessarily being synonyms or fitting into a defined hierarchy. – Related Terms (RT) can be used to show these links within thesaurus. “CHURCH RT Churchyard RT Crypt RT Presbytery” Example from RCHME Thesaurus of Monument Types, © RCHME 1995. 7
Scope Notes • Thesaurus entries can often be terse, and difficult to interpret for the nonexpert. – Scope Notes (SN) serve to clarify entries and avoid possible confusion. They serve to embody the underlying concept, rather than the language-specific word. “CHITTING HOUSE SN A building in which potatoes can sprout and germinate” “FERRY SN Includes associated structures” Examples from RCHME Thesaurus of Monument Types, © RCHME 1995. 8
Why do we need them? • LOM, DC, etc are international, and very general • Subject, Level, etc are empty buckets into which to pour values – P 1, Primary 1, Early Years, 5– 6 all roughly synonymous – Hardly very helpful to the user – Consistent use of a term, or system–level mappings between terms, allow recall of all resources. 9
Where do we get them from? • Good question! • ‘Subject’ – LCSH, Dewey, etc. – HILT – UK GCL • Education–specific – British Educational Thesaurus – MEG Levels. 10
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