Page 165 - DLIS402_INFORMATION_ANALYSIS_AND_REPACKAGING

Information Analysis and Repackaging

Notes Post-co-ordinated indexing where terms are combined at the time of searching would reduce this
effect but the onus would be on the searcher to link appropriate terms as opposed to the information
professional. In addition terms that occur infrequently may be highly significant for example a new
drug may be mentioned infrequently but the novelty of the subject makes any reference significant.

One method for allowing rarer terms to be included and common words to be excluded
by automated techniques would be a relative frequency approach were frequency of
a word in a document is compared to frequency in the database as a whole.

Therefore a term that occurs more often in a document than might be expected-based on the rest of
the database could then be used as an index term, and terms that occur equally frequently throughout
will be excluded. Another problem with automated extraction is that it does not recognise when a
concept is discussed but is not identified in the text by an indexable keyword.

Assignment Indexing

An alternative is assignment indexing where index terms are taken from a controlled vocabulary.
This has the advantage of controlling for synonyms as the preferred term is indexed and synonyms
or related terms direct the user to the preferred term. This means the user can find articles regardless
of the specific term used by the author and saves the user from having to know and check all possible
synonyms . It also removes any confusion caused by homographs by inclusion of a qualifying term.
A third advantage is that it allows the linking of related terms whether they are linked by hierarchy
or association, e.g., an index entry for an oral medication may list other oral medications as related
terms on the same level of the hierarchy but would also link to broader terms such as treatment.
Assignment indexing is used in manual indexing to improve inter-indexer consistency as different
indexers will have a controlled set of terms to choose from. Controlled vocabularies do not completely
remove inconsistencies as two indexers may still interpret the subject differently.

Index Presentation

The final phase of indexing is to present the entries in a systematic order. This may involve linking
entries. In a pre-coordinated index the indexer determines the order in which terms are linked in an
entry by considering how a user may formulate their search. In a post-coordinated index, the entries
are presented singly and the user can link the entries through searches, most commonly carried out
by computer software. Post-coordination results in a loss of precision in comparison to pre-
coordination.

Depth of Indexing

Indexers must make decisions about what entries should be included and how many entries an index
should incorporate. The depth of indexing describes the thoroughness of the indexing process with
reference to exhaustively and specificity.

Exhaustive Index
An exhaustive index is one which lists all possible index terms. Greater exhaustive content gives a
higher recall, or more likelihood of all the relevant articles being retrieved, however, this occurs at the
expense of precision. This means that the user may retrieve a larger number of irrelevant documents
or documents which only deal with the subject in little depth.

160 LOVELY PROFESSIONAL UNIVERSITY