Identifier Types in MODS data

There are twenty (!) identifier types in the MODS data:

1. egf--textgroup created to represent those authors in the Epicorum Graecorum Fragmenta without TLGs to use as canonical identifiers for the creation of CTS-URNs
2. ctsurn-canonical text services URN-used to uniquely identify a textgroup/work/version
3. lccn--Library of Congress Control Number-a unique control number assigned to an edition owned by the LOC
4. oclc--Online Computer Library Center-A unique identifier for a an OCLC bibliographic record
5. oca--Open Content Alliance-A open access digitization project of the Internet Archive-the OCA number uniquely identifies a digitized version of a book
6. fhg--Fragmenta Historicorum Graecorum--textgroup created like egf above to allow the creation of CTS URNs for fragmentary authors in this five volume series that do not contain TLG IDs to use as canonical identifiers
7. ieg--Textgroup acronym created for Delectus ex iambis et elegis Graecis to support CTS URN creation
8. isbn--International Standard Bibliographic Number--a unique ID for a printed edition
9. lyg--Textgroup acronym created for Lyra Graeca (see egf, fhg and ieg above) to support CTS URN creation
10. plg--Textgroup created for Poetae lyrici Graeci to support CTS URN creation
11. tlg--Thesaurae Linguae Graecae--a classical canon used for canonical identifiers for CTS URNs for Greek authors
12. Perseus:abo--A legacy Perseus identifier-abo stands for "Abstract bibliographic object" and was included in many MODS records to link the Perseus Catalog data to earlier data files
13. stoa author-text--A "unofficial" canon of Latin authors used for canonical identifiers for CTS URNs that Perseus has "adopted" and used to create identifiers for
14. phi--Packard Humanities Institute-a classical canon used for canonical identifiers for CTS URNs for Latin authors
15. uri--Uniform resource identifier
16. ddc--Dewey Decimal Classification
17. ark--Archival resource key--a URL and persistent identifier (found in only a few records)
18. manuscript--Used in a small number of MODS records to indicate a unique manuscript identifier that was important to the resource description
19. Perseus--Identifier used to reference Perseus document IDs
20. bhl--Bibliographica Hagiographa Latina-another textgroup identifier

A description of the significance of each should follow...