* Guest post by Rebecca Green*

The entry at 930-990 is the starting point for building a large portion of the numbers in that span. An add instruction there calls first for adding notation from Table 2 to base number 9. For example, **952 History of Japan** is built with base number **9 History and geography**, plus notation 52 from **T2--52 Japan**. The add table under 930-990 then provides for notation to be added for historical periods (930-990:01-09) or for standard subdivisions (930-990:001-009), including ethnic and national groups (930-990:004).

If the number is to reflect a particular historical period, the instructions tell the classifier to "add to 0 the historical period numbers following 0 from the appropriate continent, country, locality in 930-990." But the number-building tool isn't omniscient. Given a specific locality, how would the tool know where to find the corresponding historical period numbers?

The editorial team grappled with this problem at length, considering more than a half dozen possible solutions. The solution that has been implemented involves the addition of numerous entries for "localities of" countries, under which is found an add table with subentries for standard subdivisions and for historical periods.

This is what we find, for example, under **952.1-952.8 Localities of Japan**:

And here are all the notes found there:

Three aspects of these entries are worthy of mention:

- Numbers built using these add instructions are able to represent locality at any level given in Table 2.
- The full range of standard subdivisions given in the add table under 930-990 is made available for use.
- The add table directs the classifier to the historical period notation appropriate to the locality.

Taken collectively, these add instructions permit the classifier to build the same set of numbers that can be built by *correctly* following the add instructions under 930-990. The difference is that, by starting at the "localities of" entry for the country, the classifier is led through the number-building process in a way that helps ensure that numbers are built correctly.

For example, let’s build the number for *The death of old Yokohama: in the great Japanese earthquake of September 1, 1923*. We start at 952.1-952.8 Localities of Japan and then add **T2—521364 Yokohama**, which leads us to this point in the number-building process:

We then navigate to **930-990:01-05 Historical periods** and click Add, which gives:

At the same time, the Hierarchy box now displays the appropriate historical period notation:

We find the correct notation for 1923, **952.032 Taishō period, 1912-1926**. Clicking Add gives us the full number:

The first 765 field in the corresponding MARC record may surprise you a little:

765 1# $b 9 $a 930 $c 990 $z 2 $s 52 $u 952

as it shows that the instructions for adding T2--52 to the base number 9 are found in 930-990--which is true--even though we didn’t start there. The next 765 field reflects where our process in building the number began by indicating that we are following the instructions at 952.1-952.8 to add Table 2 notation, T2--521364:

765 0# $b 952 $a 952.1 $c 952.8 $z 2 $r 52 $s 1364 $u 952.1364

Note that "localities of" entries have been added carefully to mirror the building of numbers allowed through 930-990. Specifically, "localities of" entries have not been added if the necessary add instructions were already present in the schedules (e.g., **935.71-935.79 Provinces of Iran to 637**). Nor have such entries been added where historical period notation is specifically blocked (e.g., **943.648 †Liechtenstein**). Lastly, "localities of" entries have not been added if there is no Table 2 notation in the downward hierarchy of the notation corresponding to the number under which period notation is found (e.g., **939.73 Carthage**,** 948.1 Norway**).

Providing "localities of" entries has been a team effort over an extended period of time. Michael Panzer and Winton Matthews designed the prototype "localities of" entry. Rebecca Green programmed the generation of the entries, while Alex Kyrios and Juli Beall joined in verifying and putting the finishing touches on the entries.

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