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https://jira.duraspace.org/browse/DS-893?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=24077#comment-24077
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Christophe Dupriez commented on DS-893:
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I understand the arguments. But I would like to insist: DCAT should make a poll
of EXISTING Use cases for attached content to DSpace items and for DESIRABLE
functionalities (this should be part of any decision process about DSpace
modifications involving a migration effort). From the results of this
inventory, a clever design (and migration path) could be proposed.
My previous comment was not really linked to any of my personal developments. I
effectively use authority lists based on DSpace collection contents to control
the relationships between items of different collections. And I suppose
versioning and linked content versioning (about which you work) is part of this
question of "cleaning" bundles.
> 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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