We've gone both from EAD to MARC and MARC to EAD and the mapping seems
quite good (we use MarcEdit for the conversions).  One thing we found
when going from existing MARC records to EAD was that MARC records
commonly lacked some fields that EAD best practices either require or
recommend -- for example the usage and access restrictions (540 and
506), language of the materials (546), arrangement (351$a), acquisition
info (541), etc.  This might arise from local MARC practices (e.g. MARC
only included a 540 field if there were some restrictions on the
collection, vs a blanket "There are no restrictions on this collection"
which is what we want in our EAD) or it might be due to workflow (e.g.,
the languages present in a collection may not be known until processing,
which may happen long after the initial MARC record is created without a
546 field or with one that just has English).

So listing out all the required/recommended EAD fields/subfields and
ensuring they're all included in the MARC records will make your later
conversion will go a lot faster.  But then you probably already figured
that out :)  A good way to test it would be to create a sample set of
MARC records to your local specs, then run them through MarcEdit to
create a skeleton EAD record and see what's missing/wrong/problematic,
then adjust the MARC specs accordingly.  (We also ended up having to
tweak the provided MarcEdit style sheets slightly to account for some
local idionsyncracies, and this kind of test would shake out those
issues as well.)

Michele

+-----+-----+-----+-----+-----+-----+
Michele Combs.
Librarian for Manuscripts and Archives Processing.
Special Collections Research Center.
Syracuse University Library.
222 Waverly Avenue.
Syracuse, NY   13244
+-----+-----+-----+-----+-----+-----+
-----Original Message-----
From: Encoded Archival Description List [mailto:[log in to unmask]] On Behalf
Of Caroline Curtis
Sent: Tuesday, April 01, 2008 3:11 PM
To: [log in to unmask]
Subject: MARC21 to EAD

Hello,
 
At the University of Colorado-Colorado Springs we are currently in the
process of implementing online access to our collections through our
library OPAC. We would like to prepare for possible future
implementation of a more advanced archival management software by
creating our MARC21 records to be compatible with EAD.If we plan our
MARC21 fields to correspond with EAD fields will this sufficiently
prepare us for any future time that we may need to export our records
from the OPAC into a different archival management software that
utilizes EAD? Has anyone else out there done this?
Thanks for any help you can offer.  
Sincerely, Caroline