A new cataloging code, Resource Description and Access (RDA) was published in June 2010 and has been undergoing tests at select libraries. RDA is a departure from its predecessor, the Anglo-American Cataloging Rules, second edition (AACR2), in that it was designed for the online environment, is more principles-based, and better accommodates formats other than print. Liz Miller has been following the development of RDA for a few years and has presented on the topic twice at the New Mexico Library Association Conference. I was delighted when she approached me about writing an article on RDA, one geared to the noncataloger. In this column, reference librarians will learn why RDA was developed, what differences they will see, and how RDA contributes to a new world of library information.--Editor A librarian is cataloging a DVD. She consults a cataloging code, the Anglo-American Cataloging Rules, second edition (AACR2), to make decisions about the pieces of information she will include in the catalog record. AACR2 also instructs her on such points as from where on the resource she should take information (for example, should she get the title information for the DVD from the title screen or from the disc label?), when and how to abbreviate words, and how to choose and construct access points. To assign subject terms, she consults a controlled vocabulary, the Library of Congress Subject Headings. She consults yet another standard, the Library of Congress Classification, to assign a class number to collocate the DVD with other resources on the same topic. In all of these processes she uses a standard digital format, Machine-Readable Cataloging (MARC), to encode the various pieces of information she has selected to include in the record. Correct MARC coding ensures the record will search and display properly in an electronic catalog. The record then becomes part of her library's Integrated Library System (ILS), Millennium. The ILS software determines how the information in the record will be searched, retrieved, and displayed in the Online Public Access Catalog (OPAC), where it will be seen by users of the catalog, including patrons and reference librarians. You may begin to see why some have compared cataloging to solving a puzzle. One piece of the puzzle is about to change. A new cataloging code, Resource Description and Access (RDA), has been developed to take the place of AACR2. The development of RDA is big news for catalogers, of course, but it has implications for reference librarians, too. This article is intended to give reference librarians an introduction to RDA. Readers will learn why RDA was developed, the principles upon which RDA is based, the differences between AACR2 records and RDA records, and why RDA is so important to catalogers yet also controversial. WHY ARE CATALOGING CODES IMPORTANT? In the past, each library would create its own catalog cards. This changed in the early 1900s when the Library of Congress began selling card sets (author, title, and subject) to other libraries. Every card set that a library purchased meant one less that had to be created locally, from scratch. This was an early instance of shared cataloging. (1) When MARC was developed in the 1960s, catalogers started creating records in electronic form. MARC made record sharing much easier because the information in the records could be exchanged between computers. (2) When a cataloger creates an electronic record from scratch and contributes it to a bibliographic utility such as OCLC, a cataloger from any other OCLC member library can download that record instead of creating its own original catalog record. (3) One crucial factor that made it possible for libraries to share records with each other was the wide adoption of AACR2. A uniform cataloging code meant that every cataloger using it was creating records in the same way. It meant that a catalog record created in Poughkeepsie could be used by a library in Tacoma. …