Collating here a few thoughts that have arisen out of a range of questions and puzzles about language codes that have arisen over past year or so, inc reference to MARC mapping . . . .
Firstly, in an essentially monolingual repository I can’t see a reason to include the language note in the portal display. To cover the exceptions when articles in languages other than English will be archived then surely the simplest add on is to enter a separate note field (originally entered in a MARC 546 in cases where repositories rely on migrating MARC records?) to make this clear. Though surely the title and abstract details themselves that are on the main display normally will tell users the language anyway. (The 546 field is a perfect place to enter “English” if one wants.)
Secondly, libraries used to using the MARC 546 field for language description as their main language identifying element may be running a risk if they rely on data in these fields to be migrated to a Dublin Core element. 546 is a free text field for language notes, not strictly for coded language values. The MARC language codes are entered in either the 008/35-37 fixed field or the 041 field or both. 546 potentially contains descriptive notes in any uncontrolled format.
eng, en, en-aus — what’s the difference?
But what of the variations one sees in standard codes for language? Frex, English can be entered as en, eng or en-aus.
eng, en and en-aus are all valid ISO/RFC standard formats for identifying the English language or English language as used in Australia.
The 3 letter code ISO 639 standard was largely derived from the MARC language codes. So default MARC entries that may appear in the 008/35-37 will be valid ISO 639 language codes.
But there is also a 2 letter ISO 639 standard code.
The reason for the difference is that the shorter code was designed for “terminologies, lexicography and linguistics” and the subsequent 3 letter code was developed for “bibliographic and terminology needs”.
For practical purposes machines harvesting repositories are not going to know the difference; they’ll read both.
See http://www.loc.gov/standards/iso639-2/faq.htm for the LOC FAQ site giving more detailed explanations.
Function of the language element
The primary function of the language element is to facilitate refined searching. International service providers obviously will best achieve this by recognizing standardized formats of data. Hence the value of having the ‘eng’ in MARC 008/35-37 and/or the ‘eng’ or ‘en-aus’ etc. in the MARC 041 to map as values for the dc.language element.