At 08:59AM on 08/02/04, Ashley Sanders <[EMAIL PROTECTED]> wrote: > On Mon, Aug 02, 2004 at 08:31:01AM -0500, Ed Summers wrote: >> As you already have found from your experiment, it's not currently >> possible. Does anyone on the list know if the MARC standard indicates > > how non integer tags should behave: as control fields (<010) or > regular >> fields (>010)? Ashley are you still here? :-) > > The MARC21 Specification book says in its Definitions list that > Control Fields "are assigned tags beginning with two zeroes." Of > Data Fields it says they "are assigned tags beginning with characters > other then two zeroes." > > So by the above definitions a tag of "00A" is a control field > whereas "SYS" is a data field.
Although in *THEORY* both alphabetic and numeric characters could be used in tags in a locally-defined MARC format, the currently defined five MARC formats in use by libraries (bibliographic, authority, holdings, classification data, and community information) utilize only NUMERIC characters for tags in the MARC21 implementation. What Ashley quoted above was the *general* MARC definition, not the definition used in any specific implementation, such as MARC21. "The MARC 21 Formats: Background and Principles" <http://www.loc.gov/marc/96principl.html> states, at 6.2: "According to ANSI Z39.2, the tag must consist of alphabetic or numeric ASCII graphic characters, i.e., decimal integers 0-9 or letters A-Z (uppercase or lowercase, but not both). The MARC 21 formats have used only numeric tags." Thus, a tag "00A" is illegal in MARC21, although one could do such a thing in one's own implementation of a MARC format (which, of course, wouldn't be "standard"). Likewise, "SYS" (although permissible in one's own implementation) is illegal in MARC21. Sometimes, you'll see "LDR" used as a 3-character abbreviation of "leader" so that it displays the same as the actual MARC data, but "LDR" is not a legal name for a tag--it's just a vendor's way of displaying normally undisplayed technical data (the first 24 characters) in a MARC record. The same web page discusses "variable control fields" (00X, that is, those that begin with 2 zeros) in section 7: "Variable control fields consist of data and a field terminator. They contain neither indicators nor subfield codes.... Variable control fields contain either a single data element or a series of fixed-length data elements identified by relative character position." All other fields are variable data fields. Thus, tags 001 to 009 are variable control fields, and tags 010 to 999 are variable data fields. (There is no defined "000" tag. Sometimes, you'll see a vendor use "000" for the leader information instead of "LDR", but it's only a display device and not defined that way.) Although in theory one could have from none to 9 indicators per variable data field, the above web page states in section 8.3: "The MARC 21 formats specify two indicator positions at the beginning of each variable data field. ... Indicators may be any lowercase alphabetic or numeric character or a blank (#). Numeric values are defined first." The second sentence above surprised me, because, traditionally, indicators in library use of MARC have always been numeric. (Maybe it's just because the digits 0 to 9 have always been able to accommodate all needs so far.) While I'm describing some of the differences between the MARC format structure in general and the specific structure of the MARC21 implementation of that general structure, I should perhaps also note that the general structure permits subfield codes up to 9 characters in length, but MARC21 (as well as USMARC before it) uses only 2 characters: a delimiter character followed by a single alphanumeric character. I hope this information clarifies some of these issues and concerns. Harvey -- =========================================== Harvey E. Hahn, Manager, Technical Services Department Arlington Heights (Illinois) Memorial Library Desk: 847/506-2644 -- FAX: 847/506-2650 -- E mailto:[EMAIL PROTECTED] Personal web pages: http://users.anet.com/~packrat
