Hi Steven
Just wanted to add that having the language field would probably be useful for more libraries than not.
So would you want the ability to restrict your search based on langague as a default search field as well? There are usually 2 sides (at least :-) to a question like this - what is in the koha DB, what is in MARC, how can that data be searched on, and how will that affect the display.... Sooo, while you can assume that pretty much any field is in the MARC record I think (with 900 odd fields it seems a safe bet :-), depending on what you then want to do with the data, you might need a field for it in the koha db as well - and to map the two together.
Albert C. responded to the listserv noting the MARC21 field 041 where language info can be coded (the predominant language of the material in hand should be coded in the 008 fixed field, positions 35-37 inclusive, and this is often considered sufficient coding if the work in question is monolingual).
If I understood Zhang's message correctly, though ("I don't need the MARC info too"), that was less of an issue than having the info in the core SQL tables (right?). That distinction brings to mind the question of whether Koha is running off of the MARC records it imports or the tables it populates, stuff which makes cataloguing staff worry.
I believe (and someone else might want to jump in and correct me here) that the answer is "both" or posibly "either". When you set up your Koha you can choose to have it running in "marc mode" or not - if you choose "not" then I believe it doesn't "show" the MARC and pretty much runs off the Koha db. I think that you can search either the koha db (smaller and faster) or the MARC db (bigger and slower). The koha db is I think a subset of the MARC db - and is basically automatically "joined" to the marc db, so that the two are kept in sync. Additional info about an item is added to the Koha part - about it's life since entering the library, which MARC isn't interested in. There is a fair amount of info in a MARC record which lots of libraries have no real use for, and give volunteer cataloguers the willies. So we have the most important fields (the must haves :-) in the Koha db. So the question here - is language a "must have". UNIDO thought it was, and it seems a few more might as well - basically it probably depends on where your library is, so it's worth having it maybe in the Koha db.
Another notendum: books can be in more than one language. This is fairly common in Canada, where federal and many provincial documents are flip-flop bilingual editions.
So an item needs a language field that is more like subjects, where you can have more than one.
Whatever the example, MARC coding allows for multiple languages being noted in the 041 but what does Koha do with that data?
I think at the moment, if you are in the MARC mode, then koha searches it if you choose for it to do so. A key thing is what do you want OPAC users to be able to search on - if you want them to search on language then you're likely to want it in the Koha db as well - as you get a bit more control I think.
Amitiés, yours, confused (as usual), Steven F. Baljkas library tech at large Koha neophyte Winnipeg, MB, Canada
hope it helps Cheers Rachel