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https://jira.duraspace.org/browse/DS-893?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=24078#comment-24078
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Mark Diggory commented on DS-893:
---------------------------------
DCAT is welcome to followup however its members deem appropriate. I think the
committers/developers are open minded and would welcome feedback from the user
community on what features they desire. Your welcome to bring whatever topics
are important to you up in the list serves and jira tasks, my understanding is
that DCAT folks read all these topics expressed in jira and listserves, and its
members are free to post their thoughts/opions here, the same as everyone else
in the community.
this dialog is a bit of a distraction from my original request to Bill. Bill,
it would still be good to see some code examples, if not, i otherwise suspect
the issue should be closed or posted to the wiki list of ideas instead, at
least until someone has resources to invest. If you have any code, I'd enjoy
reviewing it for you.
> suggestion for a re-implementation of Bundles in the DSpace data model
> -----------------------------------------------------------------------
>
> Key: DS-893
> URL: https://jira.duraspace.org/browse/DS-893
> Project: DSpace
> Issue Type: Improvement
> Components: DSpace API
> Affects Versions: 1.8.0
> Reporter: Bill Hays
>
> Preliminary ideas for a new implementation of "Bundle" in the DSpace data
> model
> Current database model relationships:
> Item <- Item2Bundle -> Bundle <- Bundle2Bitstream -> Bitstream
> Current java object model relationships:
> Item <-> Bundle <-> Bitstream
> Proposed database model relationships (1):
> Item <- Item2Bitstream -> Bitstream(id, ..., bundlename, ...)
> or even more succinctly:
> Item <- Bitstream(id, item_id, bundlename, ...)
> In current DSpace, there is no realized benefit from the container complexity
> in the current model for Bundles.
> This first step in the proposal removes the Bundle table and directly
> associates Bitstream to Item. The concept of "bundle" is replaced by an enum
> field in the Bitstream that identifies a bundle type (ORIGINAL, THUMBNAIL,
> etc). Functionally this is very similar to what we get now: A bitstream
> belongs to one item and is associated with one bundle. The bundle names are
> not constrained, but some names are expected in various parts of the
> codebase.
>
> Proposed database model relationships (2):
> Item <- Bitstream -> MBundle(id, name, collection_id, derivative ...)
> This variation replaces the bundlename enum with a new class and database
> table "MBundle." Here bundles are not implemented as containers but are an
> associated type concept for a bitstream. With the association to a
> collection, bundles can be managed per collection or use a default set.
> Other properties of MBundle can be added to further enhance management
> capabilities, e.g.:
> isDerivative - identify bundles for Thumbnails and DerivativeText
> isVisible - indicate that the related bitstreams should be visible in
> display contexts
> isReserved - such as for very large "source" objects not for display or
> filtermedia
> [needs work - how complex does bundle "metadata" need to be?]
>
> Issues:
> Primary Bitstream Id: This is currently only used for the ORIGINAL bundle,
> so conceptually there is one per item. Note that the current model (API and
> database) allows for multiple ORIGINAL bundles which therefore allows
> multiple primary bitstream ids; however, the implementation doesn't expose
> this possibility.
> Possible replacement API calls, depending on the implementation:
> item.setPrimaryBitstream(Bitstream b)
> bitstream.isPrimary(Boolean b)
> Various db solutions:
> item.primaryBitstreamId - not standard database normalization but
> consistent with dspace practice
> item2bitstream.primaryBitstream - a boolean, standard normalization but
> requires some management to avoid duplicates
> mbundle.primaryBitstreamId - not standard database normalization but
> consistent with dspace practice
> item.primaryBitstream - a boolean, standard normalization but requires
> some management to avoid duplicates
>
> In the event that someone has used primaryBitstreamId in non-ORIGINAL
> bundles for special purposes, only 3 or 4 would work.
> Affected Java code: Item and Bitstream would need to be adjusted. This is
> fairly low-level so should not be visible to much of the API. Group
> authorizations would need some work (this has not been fully analyzed).
> Custom code that uses the API might be affected. Custom SQL such as for
> reporting might break, but the replacement is shorter code. Collection
> management of bundles types would need a new tab on the collection page
> (XMLUI).
>
> Upgrading a DSpace instance: The database can be modified with queries. No
> affect on assetstores.
>
> Benefits:
> Simpler, more concise model which removes unused/unnecessary containership
> structure.
> Enhanced bitstream management with bundle properties.
> Enumeration of names instead of uncontrolled strings, preventing typos in
> bundle names (e.g. from ItemImport)
> Provides easy solution to making derivative bitstreams visible.
> Moving bitstreams between bundles does not require deleting and re-adding
> the bitstream.
> Fixes data model problem with primary bitstream and multiple bundles with
> the same name
> Drawbacks:
> Not a backwardly compatible change. A fundamental change to the data
> model.
> Custom SQL code connecting using bundles will require rework.
> Summary:
> Bundles are categories for Bitstreams and do not need to be imlemented as
> containers.
> Bundles could be improved with added metadata and management features.
> The current Bundle implementation may not be a priority issue to merit the
> work suggested. However, the ideas
> above may be suggestive for other work, including metadata for all DSpace
> objects and exposing the data model
> to external systems (e.g. Fedora)
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