Glossary
WorkId
The numeric identifier of an item in the Windows Search property store; it matches the DocumentID of the gather table and links both halves of the index.
Every item in the Windows Search index has a WorkId: the WorkID column of SystemIndex_PropertyStore in Windows.edb, or the WorkId column of SystemIndex_1_PropertyStore in Windows.db, where each property of the item is a separate row sharing that WorkId.
The same number appears as DocumentID in the gather table SystemIndex_Gthr. Joining on it gives the gatherer's view of the item (scope, file name, last modified), and a WorkId with no DocumentID counterpart is a candidate for a file deleted after indexing. See Windows.edb vs Windows.db.