The RDA definition of series is: "A group of separate items related to one another by the fact that each item bears, in addition to its own title proper, a collective title applying to the group as a whole. The individual items may or may not be numbered." Note that the definition applies to both serials and multipart monographs.
Series issued as (generally) irregular serials are sometimes called monographic series; as serials, monographic series are intended to be issued indefinitely. Generally items in a monographic series are single part monographs issued on an irregular basis. For printed materials the bibliographic record for the monographic series as a whole is entered in the MARC21 Serials format with 008 Type of Serial:m.
A series may also be issued as a multipart monograph (mpm), i.e. with an intended conclusion. A multipart monograph series should be entered in the MARC 21 Books format.
Series may be classed-together (all items have the same call number; call numbers are distinguished by the volume number) or classed separately (each item in the series has a different call number). A series may be analyzed (separate bibliographic records created for the each distinct item in the series) or not. A series may be analyzed whether it is classed-together or classed separately; a classed separately series must be analyzed.
If a series is on standing order, a bibliographic record in Serials or Books format is always created. Series bibliographic records contain standard MARC fields with appropriate content designation and sufficient information for positive identification.
A bibliographic record generally is not created for a monographic series that is not received on standing order, although the cataloger may use that option for some classed-together situations. For mpm series not received on standing order, a bibliographic record is always created if the set is classed-together; a bibliographic record is not created if the set is classed-separately.
Bibliographic records for analyzed monographic series are used primarily as a hook to the Voyager Acquisitions line item and to ensure that acquisitions staff use the established form of the series and follow local classification decisions. The minimal encoding level is 7. The bibliographic record is suppressed from public display if the series is classed separately. In current practice, the bibliographic record is suppressed if the series is classed-together analyzed unless some parts lack distinctive titles. If the decision is to display the record to the public, the record may follow the same minimal standard used for classed-separately records if no cataloging copy is available. Because non-roman units catalog in OCLC, their series bibliographic records must be cataloged at E/L 7 and they may choose to create their preliminary records on the utility as well.
Bibliographic records for classed-separately multipart series on standing order are suppressed from public display and may remain at E/L 7. Bibliographic records for classed-together multiparts are always displayed and are always upgraded to full or core-level.
Because the series bibliographic record is used by acquisitions staff to determine the form of series used on analytics and to determine local classification practice, the first volume received for any new standing order series should be routed to the appropriate cataloging unit for priority cataloging. The cataloging unit is responsible for deciding whether the series will be classed together or classed separately, for creating or updating a series authority record for the series if necessary, and updating the bibliographic receipt records where necessary (e.g., for title changes or entering local classification decisions, or in some cases to full-level standard).
In a separate section, Bibliographic Records for Monographic Series & MPMs: Cataloging Policies and Procedures, standards and procedures are described for cataloging staff with responsibility for updating the bibliographic record for the series to conform to the established form of the series title.