Library of Congress Online Catalog: Help Pages

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  Basic Search Overview
  Keyword Searches:
  - Keyword
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  - Author/Creator
  - Subject Keyword
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  Other Searches:
  - Expert Search
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Keyword (match all words)

Use Keyword (match all words) searches when it is not clear where words or phrases relating to the material for which you are searching are likely to fall in catalog records, when terms may appear in different places in different records, or when there are no results using other types of searches.

Keyword (match all words)
finds words or phrases located anywhere in the catalog record.

Because the keyword search is set up to look for any of the words entered and because of the very large size of the Library of Congress database, keyword search results can be imprecise. The records will display according to the system's evaluation of their relevance.

Search limits are available.
Boolean AND operator is automatic.

Basic Search Examples:

Search string . . . Retrieves catalog records containing . . .
"history of analog comput?" history of analog: computer, computers, computing, computation, etc.
"eating and drinking" the exact phrase; would be different from the search "eating drinking" or "eating & drinking"
col%r photography the word photography and the word color, colur, coler, etc. (% is used to replace a single character)
jo?nson catalog? both words: joynson, johnson, johannson, etc. and catalog, catalogue, cataloger, etc.

Search Tips:

  • Enter words or phrases in any order.
  • All words will be searched (including articles and conjunctions in all languages, such as and, or, not, the, a, la, das, etc.).
  • Enclose words in " " (quotation marks) to retrieve the exact phrase (e.g., "tax reform")
  • Use a ? (question mark) to replace multiple characters either inside or at the end of a search term (e.g., ecumen? will retrieve ecumenical, ecumenism, etc.).
  • Use a % (percent sign) to replace a single character) either inside or at the end of a search term (e.g., col%r will retrieve color, coler and colur, but not colour).
  • Search results are ranked using a relevancy algorithm. To improve the relevancy of the results it is usually better to include more words or phrases in the search, in addition to using the suggested punctuation tools.

About Relevancy Ranking:

Keyword search results are displayed as a Keyword Titles List in ranked order using a special relevancy algorithm. While relevance ranking is used by most Web search engines, each formula for determining relevance is a little different. Here is some information on the ranking factors used in the Library of Congress Online Catalog:

  • Uniqueness of search terms within the database
  • Proximity of search terms to each other within the catalog record
  • Number of times a search word is present in catalog record fields (e.g., subject heading field, author field, title field) in which the terms occur.
Alternative Search Options:

If specific information is known (e.g., an author, title, subject term, etc.), it is better to use a Basic Search (other types) or Guided Search (offering guided structuring of Boolean and index-limited searches).

If a Keyword search retrieves too many catalog records (a common problem with Keyword searching), try using a combination Keyword and Subject search by following these steps:

  • Within the Keyword search box, type in words and/or phrases in any order.
  • Review the results list and identify a relevant catalog record.
  • Select the Subjects/Content tab to review the displayed subject headings.
  • Perform a new search using one of the relevant subject heading by selecting its hypertext link.

Use the browser's [Back] button to resume searching.

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July 15, 2008