Content and Carrier in MARC

Carrier information in MARC is found in fields 007 (for coded information) and 300 (Physical Description). One has to look beyond the terms themselves in order to get a clear idea of what the different fields and codes represent. For example, there is an 007 field that represents "Map", but this is defined as: "... special coded information about the physical characteristics of cartographic material other than a globe." The term "map" is used as a shorthand, and in this case cannot be assumed to refer to maps as content.

Content is covered by the Leader and the General Material Designation (GMD).

There is not a clear division in any of these, however, between content and carrier. This is not only a MARC format issue -- in some cases, content and carrier are defined together in our language terms. The term "globe," for example, implies both the content (a map) and the carrier (a sphere). There is nothing simple about defining these two intertwined aspects of information or cultural resources.

Leader 06/07

007 Physical Description

General Material Designation

300 Physical Description and Extent

MARC field 300 is for Physical Description. This is where you find the display form of all of the terms of measurement of the described resources in the bibliographic record:

12 slides
1 audiocassette
1 map
box 16 × 30 × 20 cm

The 300 field is primarily a statement of extent of carrier, but in some cases the statement contains a mix of content and carrier.:

map (1 sheet)

The attempt to separate content and carrier in FRBR brings up some questions about the extent of content vs. the extent of carrier. For example, in this statement:

14 film reels (157 min.)

The length of time in minutes is generally considered to be a statement about the extent of content.

There is a controlled vocabulary for carriers in RDA and presumably a controlled list is inherent in AACR2 as well.  The RDA list has 54 entries that are in 8 categories:
audio carriers
computer carriers
microform carriers
microscopic carriers
projected image carriers
stereographic carriers
unmediated carriers
video carriers

These categories are covered by

Note that one of the examples above, "map," is not included in the list of carriers. Nor is the most common extent used, "pages."* These are described in their own lists, "Extent of cartographic resource" and "Extent of text." Why are these separate from other carriers? The answer is: Because they are not carriers, they are types of content. The carrier of a map is either a globe or a sheet, but map is not a carrier, it is a type of Expression, as is text.

It turns out that cataloging has been mixing content and carrier descriptions in the extent area for ... well, perhaps forever.
1 map on 4 sheets
1 atlas (xvii, 37 pages, 74 leaves of
plates)
1 vocal score (x, 190 pages)

In addition, when describing books the carrier isn't mentioned at all, just the content:
xvii, 323 pages

unless there is no extent to the content, at which point the book is called a "volume:"
1 volume (unpaged)

I have no doubt that there are clear rules that cover all of this, telling catalogers how to formulate these statements. Yet I am totally perplexed about how to turn this into a coherent data format. In FRBR, there is something called "extent of content" as an attribute of the Expression entity:

4.3.8 Extent of the Expression
The extent of an expression is a quantification of the intellectual content of the expression (e.g., number of words in a text, statements in a computer program, images in a comic strip, etc.). For works expressed as sound and/or motion the extent may be a measure of duration (e.g., playing time).

while "extent of carrier" is an attribute of the Manifestation entity:

4.4.10 Extent of the Carrier
The extent of the carrier is a quantification of the number of physical units making up the carrier (e.g., number of sheets, discs, reels, etc.).

RDA does not have "extent of content," in part (I am told) because it would have separated the instructions for formulating the extent of content and carrier between chapters 7 and 3, respectively, and thus made it difficult for catalogers to create this mixed statement. Of course, one possible response might be that we shouldn't be creating a mixed statement, but two separate statements that could be displayed together as desired. These statements should probably also be linked to the content or carrier vocabulary term that is now carried in MARC 336, 337, or 338.

I looked at ONIX to see how this might have been handled by another bibliographic schema, and it appears that ONIX has two different measures: extent, which is used for extent of the content, and measure, which measures the physical item.

We have to clear up inconsistencies of this nature if we hope to produce a rational format or framework for bibliographic data. Dragging along practices from the past will result in poor quality data that cannot interact well with data from any other sources.

* I can't find "box" anywhere in any list, but perhaps I am missing something.