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Content and carrier

Page history last edited by Karen Coyle 9 years, 6 months ago

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.


The primary issue in MARC is that the various places in the record where content and carrier are treated are not coordinated among themselves. In particular there is no direct correlation between the coded values (Leader and 007) and the textual values (300 and GMD).


Leader 06 Type of Record


The Leader 06 code indicates the primary format of the resource being described in the record. This code has multiple functions: it has driven the cataloger input template in systems; it has been used to mark records for users or allow selection by type. The types are:


06 - Type of record

a - Language material
c - Notated music
d - Manuscript notated music
e - Cartographic material
f - Manuscript cartographic material
g - Projected medium
i - Nonmusical sound recording

These are primarily content descriptors. The one that might not be is "g - Projected medium."  In the RDA/ONIX framework that re-defines content and carrier for RDA, the attribute "projected" is a carrier, not content. Given, however, that this data element was intended to drive the record type, the use of "projected medium" may have served that purpose.

It isn't clear what the need will be for record type in the future. In any case, it would be good to recognize a practical need for a record type that drives input forms and not use that type to infer content or carrier in a more formal sense.


007 Physical Description


The 007 is a fixed field with coded physical description for the following general formats:


Electronic resource
Tactile material
Projected medium
Non-projected graphic
Motion picture
Remote sensing image
Sound recording


Each of these can have sub-formats. Note that "projected medium" appears both in the Leader and in the 007, confirming that it crosses the content/carrier barrier. It could also be argued that Motion picture is a particular type of projected medium, but it probably gets its own 007 category because of its importance as a resource and content type. Map and Globe are somewhat ambiguous, at least in natural language terms. Map would be used both for sheets and for atlases, and therefore is mainly content; Globe is only used for cartographic materials (no "snow globes").


General Material Designation


The GMD is a general statement of the type of material that is primarily intended to give the catalog user an immediate indication of the nature of the resource. 


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)

1 map on 4 sheets
1 atlas (xvii, 37 pages, 74 leaves of
1 vocal score (x, 190 pages)


"Book" or "printed pages" is a kind of default in MARC, because the number of pages (possibly content) is given without mention of the carrier (bound volume) in most cases:


149 p.


However, multiple volumes are indicated without adding the extent of the volumes (at least in most cases):


11 v.


In this way, the MARC 300 field gives the user a quick view of the extent that needs little interpretation. It isn't necessary to give "1 volume, 149 p." nor to indicate "v. 1 356 p., v. 2 420 p.," etc. for the multi-volume work. For data processing purposes, however, there is nothing to indicate that "149 p." is a volume, and in any algorithm it will not be useful to compare pages to volumes.


There is no place in MARC to indicate the extent of the content, so they become mixed in the extent area. Note that the ONIX record format uses "extent" for extent of content and "measurement" for extent of carrier. The ONIX interest in the extents is probably different to that of libraries, since ONIX is primarily about the carrier as product and inventory, not as identification.


Separating Content from Carrier


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. However, printed text is generally described as the number of pages; the same text will have a different number of pages depending on font, layout, and the size of the book. It isn't clear to me if number of pages is content or carrier. For digital texts, it is possible to indicate the number of words, which is closer to the content than the number of pages because it doesn't depend on the physical layout. Similarly, the size of a digital file that carries the same text can be different for different formats (PDF vs. Word, for example). 


A neat separation of content and carrier may not be possible, but we should at least place each term in a list where it can be understood by others. 


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


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
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.
, 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.

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