back to MARC elements

MARC Indicators

The indicators in MARC pose a number of problems because of the great variety of meanings and ways that they have been used. Like all of MARC, the indicators were designed to be understandable to humans but not to have the rigor required for most machine processing.

Defined

Each variable field begins with two positions before the first subfield. These are known as the first and second indicators. The indicators are not always defined; in fact, in about 60% of the tags one or both indicators is not defined and is therefore always left blank in instance data. Unfortunately, in some indicators the blank is a meaningful value. This practice was recognized as problematic after a while, but some instances of this remain.

Indicators are displayed in various ways in MARC displays.  MARCEdit uses backslashes for blanks in the indicator positions:

=082  0\$a813/.54$219

=100  1\$aWallace, Carol,$d1955-

=245  10$aWelcome to Mount Merry College 

The LC Catalog uses an underscore:

043 __ |a n-us---

050 00 |a ZA3250.U6 |b C68 1997

082 00 |a 025.04 |2 21

100 1_ |a Coyle, Karen.

I have not seen any examples of instance data that distinguish between blank indicators and undefined indicators. In fact, I think that distinction isn't possible in instance data. 

Types of Indicators

Identifying sources

A large number of the indicators are used to identify the authoritative source of some of the data in the field. I say "some" of the data because MARC fields are designed around display, not semantics, and therefore can contain subfields that cover more than one logical data entity. The indicators that identify sources give the information that would normally be included in a URI; that is, they provide uniqueness for the data in the subfields, and they indicate the authoritative source of the data.

The indicators have a variety of names:

code source 9052, 072)

national bibliographic agency (016)

number source (086)

source of call number (050, 060)

source of classification number (082)

source of code (041, 047)

source of term (656. 657)

subject heading system/thesaurus (600, 610, 611, 630, 648, 650, 655)

In most cases, the indicator has values ranging from 0 to 5 or 6. Any source not included in that value list is given in the subfield $2. Indicator value 7 means "Source specified in $2," and therefore serves as a re-direct to the $2 subfield. There are two significant aspects to this: the first is that the subfield $2 has the same role as an indicator even though it is a subfield; the second is that the $2 represents a much expanded list of possible sources. Fortunately, the $2 is not free text but takes its values from the MARC source codes for vocabularies, rules and schemas.

Remainders from card production

There are some indicators that are probably not used at all today (or at least I hope not). These are:

• Display constant controller
• Note controller

These were used when cards were produced by vendors and represented printing options for the cards and card sets. These types of options are now included in online systems and I would be surprised if libraries coded them on a record-by-record basis.

Note controller is binary ("display note" "do not display note"). Display constant controller often has two choices: a display constant or no display constant.

My feeling is that we can ignore these in the current environment, but I will try to find out if any systems still use them.

"Existence in x collection"

There are four call number fields (050, 055, 060, 070) that include a binary element for whether the item is in the related collection, e.g. "Existence in NAL collection" on the NAL call number tag (070). This happens to be an indicator, but it really is a binary data element relating to holdings. In the section on the 0XX fields, I treat these as free-standing data elements. My thinking is that their placement on the fields for the call numbers is convenient but the information is about the primary resource of the record.