Merging Controlled Vocabularies for More Efficient Subject-Based IR Systems

2. Lcsh And Thesauri As Controlled Vocabularies For Pre- And Post- Coordinated Subject-Based Ir Systems

As stated in Harper and Tillett (2007), there are various types of controlled vocabularies concerning the assignment of values to the “subject” metadata element. LCSH and thesauri seem to be the predominant options for such a task.

According to the LCSH guidelines (Library of Congress, 2007), subjects employ verbal strings for the description of the resources within a repository. They, also, define relations between these strings in order to demonstrate the synonyms and the associations between the subjects. A subject consists of the main heading, which corresponds to the prevalent concept of the resource. In case of resources adhering to more specific concepts, the main heading can be further specialized with subdivisions. Such subdivisions represent various aspects of the main heading. There are four types of subdivisions according to the LCSH guidelines; topical, form, geographical and chronological subdivisions. The LCSH guidelines impose certain restrictions concerning the order of subdivisions within a subject. More specifically, such order normally conforms to the pattern 'topic-place-time-form':

• [main heading] -- [topical subdivision] -- [geographical subdivision]

• --[chronological subdivision] -- [form subdivision]