A major change from AACR2 is the introduction of three MARC fields: content type, media type, and carrier type, which go in fields 336, 337, and 338, respectively. These replace the information that in AACR2 was contained in the general material designator (GMD), which went in the “$h” subfield of MARC field 245. The GMD was considered imprecise and will no longer be in use in RDA records. A description of the three new fields follows.
Content type (field 336) is “a categorization reflecting the fundamental form of communication in which the content is expressed and the human sense through which it is intended to be perceived” (RDA 18.104.22.168). Got that? It is most useful to look at the list of content type terms here: http://www.loc.gov/standards/valuelist/rdacontent.html. (The terms are also listed in the RDA Toolkit.) These include terms such as “performed music,” “spoken word,” “text,” and “two-dimensional moving image.” This is a closed list, and catalogers should not use terms that are not on the list.
Media type (field 337) is “a categorization reflecting the general type of intermediation device required to view, play, run, etc., the content of a resource” (RDA 22.214.171.124). (Note that content type is in chapter 6 of RDA because it describes expressions; media type is in chapter 3 because it describes manifestations.) Basically, media type tells you what you need to do to access the content of the resource. If you have only to cast your eyes upon it, it is “unmediated.” Otherwise, it may be “audio,” “computer,” “video,” etc. The list of 10 prescribed terms can be found here: http://www.loc.gov/standards/valuelist/rdamedia.html. Again, this is a closed list.
Carrier type (field 338) is “a categorization reflecting the format of the storage medium and housing of a carrier in combination with the type of intermediation device required to view, play, run, etc., the content of a resource” (RDA 126.96.36.199). Chris Oliver adds that “[c]arrier types are closely correlated with media types and can be considered as the next level of granularity for the media types” (53). For example, a resource with media type “audio” might have carrier type of “audio disc” or “audiocassette.” A resource with media type “video” might have carrier type “videocassette” or “videodisc.” The (long) list of possible carrier types can be found here: http://www.loc.gov/standards/valuelist/rdacarrier.html. Again, it’s a closed list.
All three fields are repeatable. For example, a CD may be able to be played in an audio device as well as a computer, so it might be given two media types: “audio” and “computer.”
The following are some examples of how these three fields will look for different resources. A basic book would be coded in this way:
336 ## text $2 rdacontent
337 ## unmediated $2 rdamedia
338 ## volume $2 rdacarrier
The “$2” subfields are mandatory. A DVD would look like this:
336 ## two-dimensional moving image $2 rdacontent
337 ## video $2 rdamedia
338 ## videodisc $2 rdacarrier
An audiobook on CD would look like this:
336 ## spoken word $2 rdacontent
337 ## audio $2 rdamedia
338 ## audio disc $2 rdacarrier
And a Web site would look like this:
336 ## text $2 rdacontent
337 ## computer $2 rdamedia
338 ## online resource $2 rdacarrier
These fields are not display fields. An ILS will have to design a way for the information contained in the 336-338 fields to map to a display in the OPAC. The display may be very similar to the GMD we have today and may thus mean a relatively small change for catalog users. However, the new fields may have important effects on the faceted searching (the “buttons”) provided by the OPAC, if these searches use information from the GMD. Information on content and carrier, etc., in the fixed fields will not change.