How do correspondence tables differ from explanatory notes?

Correspondence tables and explanatory notes do different jobs. A correspondence table shows the relationship between categories in two versions, or between two classifications, with a type for each relationship. An explanatory note defines the content and scope of one category, with inclusions, inclusions also, and exclusions. A move between versions cannot be understood from one source alone. The table shows that a move happened and what type it is. The notes show what the move means for the scope of each category involved.

What does each source contain?

The correspondence table contains rows that pair old and new categories, grouped by type. The manual passage on correspondence types gives the four types and their counts, and cites the table version. The table itself, on ShowVoc, contains the detailed rows for every class, in both directions. The explanatory notes contain, for each position in the structure, a description and annotations defining includes, includes also, and excludes, together with index entries that list detailed activities. The manual states that the notes consist of those two parts, descriptions and annotations, and index entries, and that the index is disseminated online through ShowVoc, where it is designed to evolve and be regularly revised.

The two sources are published together in the manual, but they occupy different parts of it. The introductory guidelines contain the passage on correspondence tables and the summary of main changes. The detailed structure contains the codes and headings. The explanatory notes part contains the notes for each position, in structure order. A reader who stays in one part of the manual will therefore see only one job. The table passage points to the notes for scope, and the notes point, through exclusions and cross references, to other categories whose relationship to the category in question is shown in the table. The cross references in the notes and the rows in the table are complementary, not duplicate, records.

Source	Question it answers	Form of the answer
Correspondence table	How does a category relate to categories in the other version?	Row with a type, old and new codes and headings
Explanatory note	What does one category include and exclude?	Description, includes, includes also, excludes, cross references
Index entry	Where is a detailed activity listed?	Activity name pointing to a class, as part of the notes

How are the two sources used together for a split?

The same sequence applies to a merger and to a many to many group, with the direction reversed or grouped. For a merger, the table shows the old classes combined into one new class, and the new note states the combined scope. For a many to many group, the table shows the joint scope identity for the group, and the notes for the classes in the group, read together, show how the internal boundaries moved. In every case, the table gives the relationship and the type, and the notes give the scope. Neither source, on its own, gives both.

What happens when only one source is used?

When only the table is used, a reader can state the type of a move, but cannot state what the new scope covers, and cannot pick a new class for an activity. That reader is at risk of presenting a one to many row as if it picked a class, or a many to many group as if it contained pairings. When only the notes are used, a reader can state the scope of a category in one version, but cannot state how that scope relates to the scope of a category in the other version, and cannot compare a series across versions. That reader is at risk of comparing two classes with the same code or heading, in different versions, as if they had the same scope, when the table shows a split, a merger, or a restructuring.

When neither source is used, and a heading comparison is used instead, the risk is greater. Headings are labels, not definitions, and the manual states that minor changes include heading changes at group and class level. A heading can change without a scope change, and a scope can change without a heading change, or with a heading change that does not show the full scope change. A heading comparison therefore cannot replace either source. It can only suggest where to look in the table and in the notes, and the suggestion must be verified in both.

What do the two sources not do together?

Together, the table and the notes still do not assign a code to a unit, and they do not confirm an entry. They state category relationships and category scopes, for statistical comparison and for tracing categories. The assignment of a unit to a class, for its principal activity, is made by applying the classification rules in the introductory guidelines to the information held about the unit, and it is made by the institute or register that holds the record. A reader who has read the table and the notes for a move has learned how the categories relate and what they cover. That reader must still confirm an entry with the institute or register, and must not present a category relationship as an assignment.

Read the table row for the relationship and its type, read the notes for the scope of each category in the row, and confirm any entry with the national statistical institute or the business register that holds the record.