Thanks for the information.
>The Mellon Fedora project is looking at both issues. The Fedora
>architecture assumes that executable code modules will change or be
>replaced over time. Executables will probably need to be upgraded or
>migrated more frequently than content. The Fedora object model makes a
>clean distinction between the content and its encoding format, and the
>executables that read content (wrapped in Disseminators). The design of
>the architecture is meant to enable the switching in and out of
>executables as needed.
>This leads to your second question. In the Cornell Fedora research we
>have the notion of a "structoid" which essentially defines a sort of
>encoding format characterized mainly by roles (e.g. "page") matched with
>formats ("image/gif"), plus some other info. In Fedora, a structoid has
>a unique identifier and thus can be registered as a known
>structural/encoding pattern. In the research version of Fedora, you can
>do a search of Disseminators that use a particular structoid pattern. We
>are currently still thinking about how this plays out in Mellon and
>METS. Maybe something having to do with METS profiles. Maybe something
>with typing of structMaps. In any event, when we identify an encoding
>format that's supported by a Disseminator, we need to speak both of
>structure (roles that different files play) and formats of different
>I'll be working with Jerry McDonough this week to firm up details on how
>we will specify the basic Disseminator notion in the METS schema. We'll
>continue to look at the finer issues in the Mellon project.
>From: Reagan Moore [mailto:[log in to unmask]]
>Sent: Wednesday, November 14, 2001 3:47 PM
>To: [log in to unmask]
>Subject: Re: [METS] Proposed METS changes from Mellon Fedora project
>For long term persistent archives, a concern is that executable code
>will become obsolete as the underlying operating systems evolve. One
>can characterize digital objects by their encoding format, and then
>identify executable code which is able to read the encoding formats.
>Will the METS system support the specification of encoding formats
>for digital objects? Is it possible to identify which Disseminators
>are able to read which encoding formats?
>>Cornell and UVA are working jointly on a Mellon-funded project to
>>develop open source repository software based on the Fedora design for
>>objects and repositories. As part of this project we would like to use
>>METS as an underlying encoding scheme for storing our digital objects.
>>We have mapped the Fedora object model to METS and most things relate
>>nicely, however, Fedora has the notion of a "Disseminator" which
>>essentially associates executable code with the object. We have a
>>proposal for the METS group to consider on allowing METS to support the
>>association of disseminators with an object. We have run our ideas by
>>Jerry McDonough and he was supportive of the concept, however, the
>>details of how we would do this requires some discussion.
>>I have sent along a set of attachments for your consideration.
>>Hopefully these will help you see what we have in mind, and not
>>overwhelm you with more detail! :-)
>>Thorny Staples and I will be attending the METS meeting at the end of
>>this week, so maybe this topic can be addressed at some point in the
>>Here's a rundown of the attachments:
>>1. proposedChanges.doc - this describes what we are thinking. If you
>>only have time to read one thing, this will summarize our ideas with
>>examples. The other attachments are complete examples of Fedora
>>encoded in METS.
>>2. METS_image_dobj3a.xml - this is a sample Fedora digital object
>>encoded in METS. It represents UVA's content model for their image
>>3. METS_Img1_sig.xml - a Fedora "Behavior Definition Object" encoded
>>METS. This Behavior Definition Object stores metadata and content that
>>essentially defines an interface for viewing images. The image content
>>object (#2 above) points to this object via a METS <mptr>.
>>4. METS_Img1_servlet.xml - a Fedora "Behavior Mechanism Object"
>>encoded in METS. This Behavior Mechanism Object stores executable code
>>that implements the image viewing behaviors defined in #3 above. The
>>image content object points to this object via a METS <mptr>.
>>5. METS_FedoraDC_sig.xml - just like #3 above, except this object
>>defines a set of behaviors for obtaining Dublin Core records from a
>>Fedora digital object.
>>6. METS_FedoraUVAtoDC_servlet.xml - just like #4 above, except this
>>object implements the Dublin Core behaviors defined in #5.
>>See you in Pittsburgh,
>>Sandy and Thorny
>>Attachment converted: Macintosh HD:proposedChanges.doc (WDBN/MSWD)
>>Attachment converted: Macintosh HD:METS_image_dobj3a.xml (TEXT/MSWD)
>>Attachment converted: Macintosh HD:METS_Img1_sig.xml (TEXT/MSWD)
>>Attachment converted: Macintosh HD:METS_Img1_servlet.xml (TEXT/MSWD)
>>Attachment converted: Macintosh HD:METS_FedoraDC_sig.xml (TEXT/MSWD)
>>Attachment converted: Macintosh HD:METS_FedoraUVAtoDC_servlet.xml