The table below describes briefly the sources for metadata for various categories of materials over time.
| Resource Category | Before Computers | Presently | Future? | Comments |
| books (monographs) | card catalogs, book catalogs | OPACs | OPACs, links to ebooks | Include online bookstores here? |
| periodicals/serials (indexed) | card catalogs, book catalogs | OPACs, CD-ROMs, websites, aggregators | OPACs, aggregators | |
| periodical articles | analytics in card catalogs, printed indexes | printed indexes, CD-ROMs, websites/databases, aggregators | websites/databases | |
| technical reports, dissertations, etc. | card catalogs, book catalogs, printed indexes and abstracts | printed indexes and abstracts, websites, databases | websites/databases | |
| archival collections | card catalogs, book catalogs, finding aids | OPACs, EAD/SGML files, websites/databases, finding aids | OPACs, EAD/SGML files, websites/databases | |
| government publications | shipping lists, card catalogs, book catalogs | OPACs, websites/databases, CD-ROMs, GILS databases | OPACs, websites/databases, CD-ROMs | |
| slide collections, image collections | individual labels, card catalogs, book catalogs | OPACs, card catalogs, book catalogs, CD-ROMs, websites/databases, thumbnails | OPACs, CD-ROMs, websites/databases, thumbnails | |
| pamphlets, vertical files, offprints | card catalogs, book catalogs, temporary files | OPACs, websites/databases | websites/databases | |
| maps | lists, card catalogs, book catalogs | OPACs, websites/databases, CD-ROMs | OPACs, websites/databases | |
| microform collections | card catalogs, printed indexes | CD-ROM, OPACs, printed indexes | OPACs, printed indexes, websites/databases? | |
| unindexed periodicals | analytics in card catalog, local cardfiles | websites/databases, CD-ROMs | websites/databases | |
| webpages | did not exist | OPACs, websites/databases | websites/databases | embedded metadata? |
| CD-ROM collections | did not exist | OPACs (collection level records only) | OPACs, websites/databases | May not survive |
| individual webdocuments | did not exist | OPACs | OPACs |
6/4/99 dih