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> Nope. ISBN was created in 1966. LCCNs exist for many resources > published before 1966. Even after 1966, not every single item that may > have been cataloged by the Library of Congress was neccesarily assigned > an ISBN by it's publisher.... All true. What I meant was that _if_ an isbn exists for an item and LC cataloged it, the LC record should have both. Many resources with and without isbns may not be in LC, so the lccn cannot be used as a substitute, but LC records can be considered a reasonably authoritative source of isbns for the stuff that they have. > Nope. I think you mean all items that have an LCCN should also have an > OCLC number. Probably true (mostly). But all items that have an OCLC > number will not neccesarily have an LCCN. You say so below "items that > were not cataloged by lc" will have oclc numbers but probably not > lccns. I misspoke but it appears you see what I mean. The relationship between oclc numbers and lccns is similar to the that between lccns and isbns. The oclc number is not a substitute for an lccn, but if a record that has an oclc number also contains an lccn, the oclc record can be considered an authoritative source for the lccn -- and an isbn if one exists. > I do not believe this is the case. But let us admit that our cooperative > cataloging corpus in fact IS not very reliable, it is full of incorrect > information. But we've got to deal with it anyway. A record that is > _missing_ an applicable identifier that it _could_ have contained may be > reliable in other respects, I wouldn't automatically assume it is not. The quality is variable, but it's the best we have and it's worth using the most reliable data available. Otherwise, inappropriate linkages start popping up. If there are relatively few, that's not a big deal, but once you get too much bad data in the system you have a real problem. kyle -- ---------------------------------------------------------- Kyle Banerjee Digital Services Program Manager Orbis Cascade Alliance [log in to unmask] / 541.359.9599