On Mon, 11 Jul 2005, Ryan Chute wrote:
> Hi all,
> Working with the PREMIS Data Dictionary and the Object Schema, we've
> noticed a number of discrepancies between the two; primarily pertaining
> to mandatory elements. I was hoping the list could provide a bit of
> clarification as to what is the precise definition of a valid PREMIS object.
> 1. Why inconsistent mandatory element definitions (Object-v1-0.xsd vs.
> Data Dictionary)?
> There are a number of elements which are mandatory according to the data
> dictionary, but not by the object schema (e.g. preservationLevel,
> objectCharacteristics, compositionLevel, format, storage). This
> introduces a second question:
In the schema, the only things that are mandatory are those that are
mandatory at all levels in the data dictionary. In the case of subelements
(that have a container element above them) they are only truly mandatory
if the container element exists.
So in the case of preservationLevel, it is applicable for representation
and file but not for bitstream. objectCharacteristics is applicable for
file and bitstream but not for representation. Same for compositionLevel
(which is also a subelement of objectCharacteristics, so wouldn't apply
unless the latter exists) as well as format and storage.
This is because we can expect to have PREMIS metadata at any of the 3
levels so we can't make it mandatory in the schema if it isn't applicable
at all levels, and we note that distinction in the data dictionary. So the
2 have to work together.
> 2. What constitutes a valid Premis Object (Object-v1-0.xsd vs. Data
> Issue 1 poses the question: "If an xml document validates against the
> object schema, is it truly a valid premis object?" In other words, if a
> record validates against the object schema, but does not contain either
> preservationLevel or storage elements, is it a legitimate premis
> object? What definition of a premis element should be observed?
So is this still a question? I would think that to validate an object
would require more than just validating against the schema if it were to
consider the levels. It would have to validate that the semantic unit
exists if it were at a given level (and we do have the semantic unit
"objectCategory" which designates the level).
^^ Rebecca S. Guenther ^^
^^ Senior Networking and Standards Specialist ^^
^^ Network Development and MARC Standards Office ^^
^^ 1st and Independence Ave. SE ^^
^^ Library of Congress ^^
^^ Washington, DC 20540-4402 ^^
^^ (202) 707-5092 (voice) (202) 707-0115 (FAX) ^^
^^ [log in to unmask] ^^
> We'd like to ensure we're implementing a standards compliant premis
> Ryan Chute
> Digital Library Research & Prototyping
> Los Alamos National Laboratory, Research Library