2. A computerized searchable repository according to claim 1 , wherein the documents are organized into sets in the storage device, and wherein: the content index is a single content index including index entries for content parts of all the documents, and the metadata index includes a plurality of metadata indexes each including index entries for metadata parts of only a corresponding set of the documents; and the linking structure includes a single content-to-metadata linking structure containing the content-to-metadata entries for all the documents, and a plurality of metadata-to-content linking structures each containing the metadata-to-content links for only a corresponding set of the documents.
5. A computerized searchable repository according to claim 2 , wherein the content-to-metadata linking structure is organized in a set-first manner to support searches limited in scope to one or more identified sets of the documents.