DATE: May 1, 1998

NAME: Changes for Number Building in the USMARC Classification Format

SOURCE: Library of Congress

SUMMARY: This paper proposes the addition of a field 764 (Rule Identification) to record the specific rule used for the calculation of a classification number using a schedule number and applying a table or subarrangement. In addition it proposes the definition of the first indicator in field 762 (Table Identification) to show the order of the application of each table while building a number. Both elements will facilitate a calculator function in an online classification system.

KEYWORDS: Field 762 (CD); Field 764 (CD); Rule Identification (CD); Table Identification (CD)



5/1/98 - Forwarded to the USMARC Advisory Group for discussion at the June 1998 MARBI meetings.

6/27/98 - Results of USMARC Advisory Group discussion - Approved.

7/29/98 - Results of LC/NLC review - Approved.

PROPOSAL NO. 98-09: Changes for Classification Number Building


The Library of Congress has converted the entire Library of Congress Classification to machine-readable form using MARC classification records. It is using the database for all of the classification products, including the printed schedules and Class Plus. The database of MARC classification records is used at the Library of Congress for maintenance and for catalogers assigning classification numbers. LC has contracted with the vendor of the software used in the online classification funtion for several enhancements that will facilitate the classification process when catalogers assign classification numbers. One of these enhancements is a calculator function which will use the information in the records to calculate a specific classification number by applying a table to a classification number span.


2.1 Definition of field 764

Because the various subject areas of the LCC were developed by different people over a long period of time, the schedules vary in many ways, including the application of tables. Tables are commonly used in classification schedules to subdivide topics and create a more specific number. The subdivisions are applied to many portions of a schedule, so a table is created once and then referenced at each place where it should be applied. In LCC the schedules vary in their rules for calculating numbers when a table is applied. For instance, one table may require that the number be added to a specified base number; another may require that the span be subarranged so that it is added to the first number and then one number subtracted; another may be simply appended to the number.

While planning for the implementation of the calculator function, LC staff examined the various tables throughout the entire LCC system and identified six different rules that are used for calculations. Currently there is nothing in the record that could tell the program which rule is followed for a particular table.

This paper proposes the addition of a new field in the USMARC Classification Format that will identify the particular rule that a table follows. It is preferable to define a standard MARC field rather than use a local one. This information may be useful for other users exchanging records between other classification systems or for classifiers to verify that the calculator has calculated the number correctly, since it will also include the text of the rule.

Field 764 could be defined in the 76X Number building fields for this information. It could be defined as follows:

    764   Rule Identification
      (both indicators blank)
      $a    Rule number
      $i    Explanatory text

The field would be input in the first record of the set of table records to which it applies. The program would translate the rule identifier (identified by numerics 1 through 6 for LCC) into a sequence of steps to calculate the number, expressed in textual form in subfield $i.

Examples with LCC:

Record for Table E1:
153   $zE1 $a.x $c.xZ $j Individual biography
764   $a4 $iSubstitute Cutter number from 153$a for "x" in table

Record for Table T1: 153 $zT1 $a15 $c127 $jHistory and country divisions 764 $a1 $iAdd table to number in 153$a or to number specified in 761$b if present.

2.2 Definition of indicator in field 762

2.2.1 Table priority.
Field 762 (Table Identification) in the Classification Format contains the identification of a table which provides an arrangement for or additions to the classification number or number span recorded in field 153. The format specifies that it may be repeated for each table if more than one table applies to the classification number or number span recorded in field 153. There is currently no way to indicate which table is applied first if there is more than one 762 field.

2.2.2 Internal tables identification.
The format accommodates two "styles" of tables used to expand classification numbers: external tables which are contained in a separate set of records and referenced in the classification records to which they pertain, and internal tables, which are embedded in the classification number record to which it applies. One problem encountered in the conversion of LCC to machine-readable form was the complexity of tables that appear internally within the schedule. In order to make it possible for a calculator function to use the data in internal tables it was decided to encode these as if they were external table records. The online system can thus more easily and consistently make use of the table data, but for the printed LCC it is desirable to print those internal tables at the location where they are applied. Therefore in creating records LC has distinguished those tables that are printed internally by coding them as 763 fields (Internal Subarrangement/Add Table Entry). This coding also serves to indicate that the table is applied after any coded as 762.

Work with coding LCC, a major classification scheme, using the format has indicated that it is desirable to have a more consistent approach to table location. LC would prefer to place all references to tables in the same field. A problem with having both a 762 and a 763 is that the only difference between the two is to control printed output; it adds more complexity because two different fields are used to do almost the same thing.

To remedy this problem, the first indicator could be defined as follows:

 Indicator 1  Table application sequence
              #   First
              2   Second
              3   Third 
              4   Fourth

It is unlikely that there will be more than three levels in LCC. The use of blank allows for keeping 762 fields as is, since in existing records the indicated table is applied first.

There are cases where the choice of table must be made by the cataloger table to use (e.g. for a 10 number range or 5 number range), so these tables would have the same level and a system would need to prompt the cataloger for a choice.


In the USMARC Classification Format:

- Define Field 764 (Rule Identification) as follows:

    764    Rule Identification
       (both indicators blank)
       $a    Rule number
       $i    Explanatory text

- Define the first indicator in field 762 (Table Identification) as follows:

    Indicator 1  Table application sequence
                 #   First
                 2   Second
                 3   Third 
                 4   Fourth

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