Search/Browse Help - Index Descriptions
Types of Indexes
The LC Catalog supports three types of indexes: keyword, left-match, and headings:
- Keyword Indexes help you to find words and phrases across most fields of the record (MARC fields 010-999). Keyword searches allow you to search using natural language terms. Keep in mind that keywords are divided by word separators such as spaces and marks of punctuation. When a record is indexed, punctuation is generally replaced by spaces to form "words" (for example: Washington, D.C. is treated as three separate words and best treated as a word phrase in keyword searches). Words can be combined into phrases or connected with Boolean operators (AND OR NOT). Truncation, wild cards, and limits are available. Keyword searches, however, cannot take advantage of the cross-references available when browsing controlled forms of author/creator names, names/titles, subjects, and series/uniform titles.
- Left-Match Indexes start with the left-most word of a single field (or subfield) in a record. These indexes often incorporate special processing for punctuation and spaces, a feature especially useful when searching numbers (for example, hyphens are automatically removed when searching for ISBNs such as 0-7474-0114-4). Many left-match indexes search across subfields; truncation, wild cards, and limits are available. Left-match searches cannot be combined with searches for data found in other fields of the record. However, individual left-match indexes can be grouped into "composite" indexes to search across multiple fields or subfields.
Headings Indexes enable you to browse lists of controlled forms of author/creator names, subjects, names/titles, and series/uniform titles. These "authorized headings" are maintained by the Library, with many terms searchable in LC Authorities. A form of headings index also supports call number browsing of items in the Library's collections.
Headings in the LC Catalog can be searched in two ways:
- Beginning with searches start with the left-most word of the heading, with terms entered exact order.
- Contains searches look for any word in the heading (with a limited number of stopwords. The default Boolean operator is AND. Wild cards can be used. Contains searches are available for author/creator names, names/titles, subjects, and series/uniform titles, but not for call numbers.
Results of headings searches are displayed as Headings Browse Lists, lists of terms ordered alphabetically or numerically, with the relationships among headings indicated by both cross-references and scope notes. Truncation and phrase searches are supported, but limits are not available. The Library's Thesauri & Controlled Vocabularies website describes the vocabularies and thesauri used in LC Catalog records. One of the Library's most common controlled vocabularies is the Library of Congress Subject Headings (LCSH).
Index Names and Search Codes
The more than 500 keyword, left-match, and headings indexes available for searching the LC Catalog are documented in two lists, one sorted by index name and one by the four-character index search code:
Configuration information for LC Catalog keyword, left-match, and headings indexes specifies the MARC fields and subfields included in each index, the sort and display parameters used for index search results, and the Z39.50 attribute associated with each index: