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Retrospective Conversion and Weeding

Retrospective Conversion is the process of converting shelf cards or pre-existing online records into machine-readable format. There are several methods for converting your existing shelf-list cards into MARC records. Typically, you search a large database such as OCLC for a given record that matches your shelf list card. Once this record is found, you download the item from OCLC or another remote database.

Finally, you customize this record, adding local information such as call number and your library's holding information. It is important that the shelf list card display adequate information in order to find the appropriate match in the remote database. One way to ensure a good match is to make sure that your shelf list or pre-existing catalog is in a standard MARC format before conversion.

Tips for Record Conversion

  • Establish a source for conversion. Will you use your shelf list, public catalog, or copy the verso (inside title page) for performing your retro-conversion? Identify one source that works best, and use it!
  • Convert the most popular items first. What circulates the most? What items or subject areas generate the most inquiries? Popular collections will be the most crucial to convert. Work your way down from here.
  • Examine Your Card Catalogs. Is there enough information available to establish a match in the database of MARC records? Is local data added to your MARC records available? (call number or copy information

What type of match are you looking for?

Is a general match sufficient; for example, as long as the title is Gone With The Wind and the author is Margaret Mitchell this match will serve your needs? Or, are you looking for more specific information for a record match such as the particular edition of Gone With The Wind? General matches require less specific information—title and publication date. If you want a closer match, you will need more detailed information such as ISBN number or Library of Congress Card Number (LCCN).

Shelf list preparation

make sure the following fields are listed on each shelf card:

  • Library of Congress Number
  • ISBN (or ISSN for periodicals)
  • Author
  • Title
  • Publisher
  • Publication date

Check the shelf list against your physical collection.

What to look for when testing data:

  • Call numbers with semicolons, or of atypical origin
  • Order records
  • Suppressed records should still be suppressed
  • Provisional records
  • Claim notes and action dates
  • Open orders by type and prices
  • Diacritics in authority and bibliographic records
  • 949 fields of bibliographic record
  • Unlinked items or short MARC records
  • Copy holding notes and 852, 866, 867, 868, and 899 fields
  • Long and/or complex call numbers (government documents, Dewey, Cutter)
  • Existing system control numbers


General Criteria for Weeding

  • Item has not circulated in five years
  • Library owns a later edition
  • Library owns multiple copies
  • Item is in poor condition
  • Refer to your library's collection development policy, for guidance in what items or category of items to weed.

For additional information, email: Regan Harper (

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