Versioning of Digital Objects in a Fedora-based Repository Matthias Razum FIZ Karlsruhe DORSDL Workshop Alicante September 21, 2006

2September 21, 2006 ECDL – DORSDL Workshop, Alicante Outline Motivation Versioning Concepts in eSciDoc Content Models Technical Approach Conclusion

3September 21, 2006 ECDL – DORSDL Workshop, Alicante eSciDoc is a joint project of the Max-Planck-Society (MPS) and FIZ Karlsruhe 6 million € five-year grant (2004 – 2009) from the German Federal Ministry of Education and Research It aims to build an integrated information, communication and publishing platform for web-based scientific work, exemplarily demonstrated for multi-disciplinary applications in the MPS eSciDoc is not a mere research project, but aims at establishing an innovative productive system Project Setup and Mission

4September 21, 2006 ECDL – DORSDL Workshop, Alicante Repositories for eScience The contents of an institutional repository or a digital library form the ‘institutional memory’ of an organization And just like human memory, they should allow for associating information objects in novel contexts, thus creating new scholarship Interdisciplinary work is becoming increasingly important, so systems have to span scientific disciplines Repositories should be open, application-independent and flexible, thus laying the ground today for repurposing the information in future applications

5September 21, 2006 ECDL – DORSDL Workshop, Alicante Turning Static Objects into ‘Living’ Knowledge e-Scholarship allows to publish all intermediate results of knowledge generation from first ideas, theories, discussions with peers to final results Institutional Repositories and Digital Libraries need to support scholars already in the early steps of this process, thus enabling their users to share their work in progress with peers Thinking a step further leads to interactive authoring environments with support for collaboration and annotations As a result, objects loose their static nature and become ‘active nodes’ in a network of knowledge

6September 21, 2006 ECDL – DORSDL Workshop, Alicante Implications The concept of ‘ownership’ of an artifact is loosened and partly replaced by an ongoing authoring process which spans persons, places, and time Collaborative authoring raises an issue familiar to software developers: versioning of digital objects All intermediate or working versions of artifacts should become part of the repository, not just the final versions Good Scientific Practice requires provenance data for objects and versioning

7September 21, 2006 ECDL – DORSDL Workshop, Alicante Outline Motivation Versioning Concepts in eSciDoc Content Models Technical Approach Conclusion

8September 21, 2006 ECDL – DORSDL Workshop, Alicante Versioning on Object Level Fedora’s basic object model – as defined in FOXML – is composed of an identifier, some key descriptive properties and a set of datastreams Currently, each change to a datastream leads to a new version of the datastream, but not of the object itself. On the other hand, authors and editors perceive objects as one coherent entity, not as a set of datastreams. They request a ‘whole-object’ versioning which complies with their mental model.

9September 21, 2006 ECDL – DORSDL Workshop, Alicante Fixed and Floating Object References Scholarly work strongly relies on citations and external references to existing material (e.g. primary data and supplementary material) In the context of digital repositories, these associations are expressed as object relations. Versioning of objects then raises the question how to handle relations pointing to a versioned object. eSciDoc implements two approaches: fixed relations pointing exactly to a given version of an object and floating relations which always point to the latest version of an object.

10September 21, 2006 ECDL – DORSDL Workshop, Alicante Internal and Public Versions Versions represent intermediate work statuses and are only visible to authors of digital objects Revisions are published versions of objects with persistent identifiers. Creating a revision is an intellectual step which most often includes some form of quality assurance, whereas versioning is an automated process.

11September 21, 2006 ECDL – DORSDL Workshop, Alicante Container Objects eSciDoc allows the grouping of objects by means of container objects like collections or bundles. A change to one of the contained objects substantially changes the container object as well. Therefore, any change to a contained object should lead to a new version of the container object. The same applies to revisioning: container objects are citable objects with their own persistent identifier. Revisioning of contained objects forces a new revision of the container object too.

12September 21, 2006 ECDL – DORSDL Workshop, Alicante Outline Motivation Versioning Concepts in eSciDoc Content Models Technical Approach Conclusion

13September 21, 2006 ECDL – DORSDL Workshop, Alicante Content Models in General An important part of implementing a Fedora repository is modeling different classes or “genre” of digital object that will be created, stored, and managed in the repository. A content model will typically describe the following: –Datastream composition the number and kinds of datastreams that must be present in the digital object the format(s) for those datastreams, either MIME or format identifiers whether each kind of datastream is required or optional whether each kind of datastream has cardinality contraints –Semantic identifiers for each kind of datastream relationships in the cases where a content model is a “graph” of related content models –Disseminators (optional)

14September 21, 2006 ECDL – DORSDL Workshop, Alicante eSciDoc Content Models Few generic object patterns: –Instances (administrative context) –Aggregations (collections, bundles) –Content Items –Licenses –Persons Genres are specialized object pattern with –Additional constraints and rules –Genre-specific metadata

15September 21, 2006 ECDL – DORSDL Workshop, Alicante Structural View of Content Item Content Item hasRevision * Content Component hasComponent * CC License hasLicense * License hasLicense * Metadata hasMD * Essential Properties hasProperties 1 eSciDoc Metadata hasDefaultMD 1 CC Metadata 1 hasMD

16September 21, 2006 ECDL – DORSDL Workshop, Alicante Content Item Modeled as Fedora Object Content Component RELS-EXT CC MD License 1... License n Content Stream hasComponent * Content Item RELS-EXT eSciDoc MD MD 1... MD n WOV MD

17September 21, 2006 ECDL – DORSDL Workshop, Alicante Container Modeled as Fedora Object Content Item RELS-EXT eSciDoc MD MD 1... MD n WOV MD hasMember * Container RELS-EXT eSciDoc MD MD 1... MD n Structure Map WOV MD

18September 21, 2006 ECDL – DORSDL Workshop, Alicante Outline Motivation Versioning Concepts in eSciDoc Content Models Technical Approach Conclusion

19September 21, 2006 ECDL – DORSDL Workshop, Alicante Whole-Object Versioning Metadata Fedora versioning works automatically within objects The eSciDoc middleware keeps track of whole object versions via objectVersion metadata The eSciDoc middleware also can tag particular whole object versions as “revisions” which will be official published views of the object

20September 21, 2006 ECDL – DORSDL Workshop, Alicante Animated View t0t0 t1t1 t2t2 t3t3 t4t4 Content Item CC 1 PID: parent:1 VersionID: 1.0 DOI: -- PID: child:1 Version: t 0 PID: child:2 Version: t 0 PID: parent:1 VersionID: 1.1 DOI: -- PID: child:1 Version: t 0 PID: child:2 Version: t 1 PID: parent:1 VersionID: 1.2 DOI: -- PID: child:1 Version: t 0 PID: child:2 Version: t 1 PID: child:3 Version: t 2 PID: parent:1 VersionID: 1.3 DOI: x.y/rev:1 PID: child:1 Version: t 0 PID: child:2 Version: t 1 PID: child:3 Version: t 2 PID: parent:1 VersionID: 1.4 DOI: -- PID: child:1 Version: t 4 PID: child:2 Version: t 1 PID: child:3 Version: t 2 CC 2 CC 3 Revision

21September 21, 2006 ECDL – DORSDL Workshop, Alicante Object Version XML this is the first whole object version demo:5 is the same; demo:6 modified; demo:7 ingested

22September 21, 2006 ECDL – DORSDL Workshop, Alicante Outline Motivation Versioning Concepts in eSciDoc Content Models Technical Approach Conclusion

23September 21, 2006 ECDL – DORSDL Workshop, Alicante Conclusion Versioning is essential for repositories which cover the whole object lifecycle Fedora already comes with a powerful versioning mechanism, but cannot fulfill all requirements of eSciDoc Atomistic content models make versioning even more complex The proposed approach provides a solution for advanced versioning requirement and at the same time is a demonstration of Fedora’s flexibility and adaptability

24September 21, 2006 ECDL – DORSDL Workshop, Alicante Acknowledgements The concepts in this presentation are based on eSciDoc’s Logical Data Model, created by Natasa Bulatovic (ZIM, Max Planck Society) a joint workshop of ZIM and FIZ with Sandy Payette and Carl Lagoze

Questions