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Comment: Migrated to Confluence 5.3

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Sakai Entity and Content Models

http://bugs.sakaiproject.org/confluence/display/MJN/Sakai+Entity+ModelImage Removed

Every Sakai Entity has the following features/capabilities:

  • URL: A URL that can be used to access this entity.
  • Reference: An internal reference.
  • Id: A globally unique (UUID) identifier.
  • Properties: A set of resource properties associated with the entity.
  • XML Form: The entity in serialized XML form.

http://bugs.sakaiproject.org/confluence/display/MJN/Sakai+Content+ModelImage Removed

ContentResource object:

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  • Sakai has migrated their Content Host Service to JCR, Sakai Wraps the JCR Factory API so that you are not exposed to how a JCR connection is retrieved, the JCR objects themselves are exposed to the user of the service so there is no need to learn another API. This presents a stronger case for use of JCR as an API for interacting with stores such as DSpace and Fedora, reuse of a Fedora JCR implementation may enable DSpace on Fedora, Sakai on Fedora, Sakai+DSpace on Fedora, etc. --Mark Diggory 17:44, 26 September 2008 (EDT)

Here is a decent document backgrounder the reasons behind th Sakai move to JCR as its Content Hosting Service http://bugs.sakaiproject.org/confluence/display/CHS/JCR+rationale+and+implicationsImage Removed

Fedora Object Model

http://www.fedora-commons.org/confluence/display/FCR30/Fedora+Digital+Object+ModelImage Removed

  • PID: A persistent, unique identifier for the object.
  • Object Properties: A set of system-defined descriptive properties that are necessary to manage and track the object in the repository.
  • Datastream(s): The element in a Fedora digital object that represents a content item.

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The entire node type hierarchy can be found in section 6.7.22.1 of the JSR-170 specification.

Image Modified

An older api overview http://www.theserverside.com/tt/articles/article.tss?l=JCRPract

  • I have concerns that JCR's use of mixin properties is a bit arduous and obtuse, I have yet to find adequate description of the mixin properties--Mark Diggory 15:36, 26 September 2008 (EDT)

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  • _I think JCR relation objects should be evaluated in comparison to the REL-EXT section of a Fedora Object. Though, I'm unsure of the update policy on object with RELS_EXT, specifically given that the relationship is stored within the Fedora Object itself. _ --Mark Diggory 17:06, 26 September 2008 (EDT)

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Fedora Relationships (RELS-EXT)

http://www.fedora-commons.org/confluence/display/FCR30/Digital+Object+RelationshipsImage Removed

RELS-EXT gives an opportunity to express relationships between fedora objects in RDF/XML, it looks something like:

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  • Per my statement above, I think that JCR is onto something here, specifically that relationships may be expressed by some "authority" other than the Object owner, as such such relationships need to be modifiable and maintained independent of the objects themselves, allowing for various authorities o assert relations independently. --Mark Diggory 17:11, 26 September 2008 (EDT)

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A Google+Summer+of+Code project in 2007 has implemented a versioning prototype, for DSpace Items, DSpace Items have two identifiers, on permanent, the other is a version lineage id. The Lineage is comprised of Items, each with unique metadata and bundles, Bitstreams within the Items will be either linked from the previous version or added anew.

http://wiki.dspace.org/index.php/Google+Summer+of+Code+2007_VersioningImage Removed

JCR

JCR Appears to Version Nodes, its unclear ATM if this results in new node ids I assume it does not, There is an explicit VersionHistory API available that gives one thability to navigate the Versions (the VersionHistory of the Node). Versions are Nodes as well.

http://day.com/maven/jsr170/javadocs/jcr-1.0/javax/jcr/version/package-summary.htmlImage Removed

Fedora

Fedora Versions Datastreams and not whole Digital Objects, this eliminates the need to generate/maintain new Object identifiers...

See for more detail http://www.fedora-commons.org/confluence/display/FCR30/VersioningImage Removed

Sakai CHS

Now based on JCR so is similarly versioned

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The Fedora API support change notification as a JMS message provider. This works via Topics or Queues.

http://www.fedora-commons.org/documentation/3.0/userdocs/server/messaging/index.htmlImage Removed

JCR

There is an explicit Change Notification API for JCR. I did uncover a recent thread exploring the topic here:

http://www.theserverside.com/news/thread.tss?thread_id=46303Image Removed

http://day.com/maven/jsr170/javadocs/jcr-1.0/javax/jcr/observation/Event.htmlImage Removedhttp://day.com/maven/jsr170/javadocs/jcr-1.0/javax/jcr/observation/EventListener.htmlImage Removed

DSpace

In 1.5 the Event Mechanism was provided as a subsystem capable of issuing events to consumers. Originally, there was a JMS consumer solution, but it was not brought into 1.5 implementation because of tractability and complexity issues with the API.

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