- Title: Objects can be associated with a PREMIS event service
- Primary Actor:
- Scope:
- Level:
- Story: An object can be associated with a listener for PREMIS events. This listener should receive event message rather than whole documents, but be able to export a log of the event history. Attempting to emulate this in Fedora 3.x requires constant replacement of an XML document, and has collision problems when integrated into a system of parallel, distributed repository processes.
Implementation Proposal:
The Fedora 4 repository relies heavily on metadata to describe and manage its digital content. There is a large intersection between the types of data Fedora uses in its implementation to manage data and the PREMIS standard for metadata that supports information necessary in the description of preserved digital objects. In fact Fedora currently relies on PREMIS to describe content nodes such as the properties premis:hasContentLocaiton and premis:hasSize.
The Fedora 4 repository also is built based on the intersection of several structural concepts. There is the legacy Fedora construction of objects and datastreams adhering to a content model definitions. There is the fedora 4 ontological description of abstract resources taking the form of objects, datastreams and content. There is the modeshape node type definitions extending a base nodetype into file and folder primary types that can be extended by the addition of mixins. The PREMIS 2.2 is structured similarly, defining abstractly intellectual entities in the form of objects classified as representations, files, and bitstreams. Given these similarities, Fedora is well situated to borrow many of the concepts defined in PREMIS in particular PREMIS's definition of an event ontology to capture actions taken on objects preserved in the repository.The kinds of actions that the Fedora repository would preserve can be divided into 2 categories, 1) preserving an object's prior event history, and events generated external to fedora and 2) preserving any events performed on the object by the repository itself. In either case the PREMIS OWL ontology provides much of the vocabulary necessary for these implementations:
"This OWL ontology allows one to provide a Linked Data-friendly, PREMIS-endorsed serialization of the PREMIS Data Dictionary version 2.2. This can be leveraged to have a Linked Data-friendly data management function for a preservation repository, allowing for SPARQL querying. It integrates PREMIS information with other Linked Data compliant datasets, especially format registries, which are now referenced from the PREMIS ontology (for instance, the Unified Digital Format Registry [4] and PRONOM [5]). Thus information can be more easily interconnected, especially between different repository databases. The OWL design of PREMIS should NOT be considered as a replacement for the XML Schema: the two of them should rather be considered complementary. Work to align the PREMIS ontology with the PROV ontology [6] is being considered."
...
<object> <rdf:type> <http://id.loc.gov/ontologies/premis.html#hasEvent> .
...
Complications:
1) The JCR events (NODE_ADDED,PROPERTY_CHANGED, etc) don't necessarily map 1:1 to all the PREMIS or other event types that one may wish to track. So the Fedora implementation of some PREMIS events may not be able to rely on the existing event machinery. In these exceptional cases, either the PREMIS may have to be coupled in the code to where the event actually takes place or a new set of Fedora events will have to be generated for the events that aren't explicitly mapped to JCR events or have the necessary information.
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Resources:
http://www.loc.gov/standards/premis/ontology-announcement.html
https://wiki.duraspace.org/display/FF/Fedora+Repository+Home
https://wiki.duraspace.org/display/FF/Properties+CRUD
https://wiki.duraspace.org/display/FF/RESTful+HTTP+API
https://github.com/futures/fcrepo4/blob/master/fcrepo-audit/src/main/java/org/fcrepo/audit/LogbackAuditor.java
https://github.com/futures/fcrepo4/blob/master/fcrepo-jms/src/main/java/org/fcrepo/jms/observer/JMSTopicPublisher.java
http://id.loc.gov/vocabulary/preservation/eventType.html
A New Eventing System
<to be described here>