[Contents]
The structure of this thesaurus is based on guidelines given in BS5723 Guidelines for the Establishment and Development of Monolingual Thesauri (British Standards Institution, 1987) and Thesaurus Construction and Use (Aitchinson, Gilchrist and Bawden, 1997). It deviates from BSI standards in that, it groups terms by class rather than the broadest noun term (Top Term). Although the British standard includes the concept of class, the broadest noun term is the Top Term. This thesaurus does not have Top Terms as the classes are not part of the hierarchy. The cultural heritage sector tends to use the singular instead of plural and that is why English Heritage thesauri use the singular, unless it affects the meaning of the term, and this is allowed for in the BS 5723.
A.1.1.1. The Equivalence relationship
Terms are either "preferred" or "non-preferred". Only preferred terms appear in the hierarchies and can be used for indexing. A non-preferred term is a term that has the equivalent meaning to the preferred term but is not used for indexing. This might be because the term is:
| a Synonym | A term with the same meaning where the preferred term is the more commonly accepted. | e.g. cabin hand bowl USE hand bowl |
| a Quasi-Synonym | A term closely related to, but not quite synonymous with, a term but treated as a synonym within a specific subject area. | NO EXAMPLES |
| a Compound Term | The term is made up of two single concepts which should be indexed separately for Thesauri purposes | NO EXAMPLES |
| a Foreign Term | English language terms used except where a foreign term has come into accepted common usage. | NO EXAMPLES |
| a Regional Term | The term is a regional term and a more general term is seen as more useful for retrieval. | e.g. longboat USE narrow boat |
| an Archaic Term | The term has passed out of common usage | NO EXAMPLES |
| Upward Posting | The term is considered too specific for the scope of the thesaurus and is usually a more specific type of the preferred term | e.g. boat registration plate USE boat plate |
A.1.1.1. The Hierarchical relationship
Preferred terms are placed into hierarchies. Terms are gathered into groups with the same concept. Then terms in each conceptual group are divided into levels going from the broadest type of term to the narrowest and most specific type of term.
| e.g. | Mersey flat | Conceptual group |
| Mersey sailing flat | Broadest level or BROADER TERM | |
| outside flat | Narrowest level or NARROWER TERM |
Here the terms Mersey sailing flat and outside flat are both types of Mersey flat but outside flat is a more specific form of Mersey sailing flat so can become a Narrower term of it.
A thesaurus can be poly-hierarchical. That is to say, a broader term can appear in more than one hierarchy and under more than one class. e.g. barge pole in two hierarchies under two separate classes.
| Classes | |
| COMPONENTS ____human powered propulsion system ________barge pole |
TOOLS AND EQUIPMENT ____components boat equipment ________barge pole |
A.1.1.2. Grouping Terms
In the creation of hierarchies it is sometimes necessary to use a grouping term in order to bring together terms with a common concept but where the grouping term itself is not to be used for indexing purposes (and is hence known as a non index term). These can be identified in this thesaurus as unemphasized, lower case terms (for example, boat equipment) whilst an index term is identified as a bold, lower case term (for example, watercan).
A.1.1.3. Facet indicators
It is sometimes necessary to specify on what basis the terms have been grouped into a hierarchy. In these instances the broadest term of the hierarchy is given a facet indicator, whereby a term is further defined by an indication of its characteristics. This thesaurus contains facet indicators, e.g. <narrow boat by type> Terms with facet indicators are non index terms.
A.1.1.2. The Associative relationship
Preferred terms can be associated with other terms that have similar concepts, but are not synonymous with each other. These types of terms are known as related terms and show an associative relationship. They are related but may not share the same hierarchy. Related terms are often used as an aid to help enquirers find terms similar to the initial term which are not always immediately obvious, in their original search. For example
Severn flat
RT up river trow
Severn flat is similar to up river trow and vice versa.
The terms within the thesaurus are grouped by classes and not the broadest noun term (Top Term). The classes are primarily concerned with the classification of waterway objects by function and as a result multi-functional object names may be assigned to more than one class. Similarly, where there are alternative interpretations of function, an object name may be assigned to several classes. These groupings have been used to aid search and retrieval but are not part of the hierarchy of terms.
Object names are included in a class on the basis of the criteria set out in the class definitions.
Within each class, groups of broad terms can be used to further sub-divide terms. These broad terms reflect the overall conceptual framework of classification by function and also other concepts used regularly for classification and retrieval within subject areas.
A scope note provides a definition of the concept to which the term applies and is to be used in the context of the thesaurus. It will occasionally include guidance for the use of the term.
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