Minor changes and additional subsections.
+## Overview
+
The add-id command copies its input file to its output file,
-adding an Id column and ID values when needed.
+adding an ID column and ID values when needed.
+
+### ID Styles
New IDs may be generated using one of several available ID generation
styles.
@@ -15,6 +19,8 @@ styles.
| wikidata | Concatenate the node1 and label column values with either the node2 column value (if it starts with P or Q) or the SHA256 hash of the node2 column value (truncated to the width giver by --value-hash-width). |
| wikidata-with-claim-id | If the claim-id column is empty, produce an ID value as per 'wikidata'. Otherwise, if --claim-id-hash-width is 0, then concatenate the claim_id column value to the `wikidata` ID value. Otherwise, concatenatea a SHA256 hash of the claim-id value, truncated per --claim-id-hash-width. |
+### Uniqueness and Memory Use
+
By default, the ID values in the file are validated for uniqueness,
using an in-memory set. This may cause
memory usage issues for large input files, and may be inappropriate
