Architecting Extensible Digital Repository Services

1. Architecting Extensible Digital Repository Services Robert Chavez, Robert Dockins, Anoop Kumar, Matthew Mcvey, Ranjani Saigal, Nikolai Schwertner Tufts University, Medford, MA Fedora Users Conference, Rutgers University, May 13 2005

2. An Overview • Digital Collections at Tufts • Reasons for developing Tufts Digital Repository (TDR) • Some design requirements and goals • The TDR architecture and services • Applications that interface with TDR • Tufts Digital Library • VUE • Future Directions

3. A Brief History of Digital Collections at Tufts • Pre-existing Digital Projects/Libraries/Collections • Perseus Digital Library • Tufts University Science Knowledgebase (TUSK-Medicine) • Artifact Image Library (Art History) • Miscellaneous projects • Crime and Punishment, Faculty Publications, Faculty Datasets, many and varied content management systems • Digital Collections and Archives (DCA) • steward of the University's permanently valuable digital records and collections • many and varied digital collections • university records

4. Why TDR? • Digital collections and materials are continually growing; adding content in a variety of formats. • Original architectures and systems were not built to accommodate such expansion. • Original architectures and systems were not built to facilitate interoperability or sharing of resources. • Needed a university-wide digital repository that could manage the ever increasing content while continuing to service discipline specific needs and leveraging existing and new tools and services. • Need for DCA to support digital data warehouse services and digital archival storage services for digital content of enduring value.

5. Who? • Digital Collections and Archives (DCA), Academic Technology (AT) • partnered to create a digital repository and digital library application for managing content while supporting teaching and learning at the university. • Roles (a bit over-simplified): • DCA: content developers, collection and deposit policy creators, managers of repository • AT: content developers, applications and overall system architects and developers

6. Design Requirements • Persistence: • Enforce unique persistent identifiers • Manage identifiers for multiple projects • Assurance that the data will be preserved and retrievable over time • Ingest: • Enforce archival standards • Ability to incorporate appraisal • Automated ingest workflow • Management: • Use of information packages to facilitate storage and dissemination • Incorporate content models • Rights/access management • Access/Interoperability: • Digital resources should be accessible to multiple applications and systems • Authorization policies must be enforced • Scalability • (Re)Usability • Leverage existing and new tools and services

7. TDR Architecture Interfacing Services Caching Service Naming Service A Application Interface U A FedoraClient P Drop Box Fedora Repository Service Application Interface U Ingestion Service Search Interface U P Search Index Indexing Service Search Service P - Data Provider A - Administrator U - User Arrows represent flow of data

8. Services of TDR

9. Current System Architecture

10. TDL Application • How it all fits together, a working application • http://dl.tufts.edu

11. General TDL application search transaction process TDL App Search Interface [JSP] Search Service Oracle Query Builder [Java App.] U Search Index Main Index [Oracle] TDL App Search Results [Search Interface] Search Service Results Collation [Java App.] Search Index XML index [Oracle] Naming Service URN-PID resolution [MySQL] TDL App Disseminator Viewer [JSP] Repository Service Object Dissemination [Fedora] U

12. TDL Architecture • Drop Box and Ingestion Service • Naming Service • Fedora Repository Service at Tufts • Indexing and Search Services • Interfacing Services

13. Drop Box and Ingestion Service • automate the process of preparing materials for ingest • validate materials before ingest • primarily for large-scale ingests • not an object factory (i.e., not a tool for building individual objects)

15. TDL Architecture • Drop Box and Ingestion Service • Naming Service • Fedora Repository Service • Indexing and Search Services • Interfacing Services

16. Naming Service • Assigns, reserves and resolves URNs • The URN has a very flexible structure that can be tailor made to suit the special needs of the particular naming convention. • Example: namespace1:namescape2:namespace:3:object_id • Manages repositories • multiple production repositories, backup repositories, etc. • Tufts URN Formats examples tufts:dca:central:MS102:33.1345 Perseus:text:1999.04.0006 97.5224.77-1729-47 • URN Properties • Provides unique ID to objects deposited into repository • Service assures resolution to unique resource. • Implementation • MySQL, Java class, JSP Management console

17. Tufts Naming Service

18. TDL Architecture • Drop Box and Ingestion Service • Naming Service • Fedora Repository Service • Indexing and Search Service • Interfacing Services

19. Fedora Repository Service • Fedora met many of our critical needs: • Modular nature of the repository service • Management of digital content over time (versioning, etc.) • Aggregation of mixed, possibly distributed, data into complex objects • The ability to specify multiple content disseminations of these objects • The ability to associate rights management schemes with these disseminations.

20. Fedora Repository Service, cont… • Tufts Implementation Details: • External data stores • Modeling behaviors and content • Piece of a larger architecture; not out of the box solution • Tufts Repository Models/Policies • Fedora @ Tufts serves several purposes • Archival/institutional repository • Guarantee functional preservation • Data warehouse • Guarantee bitstream preservation • Active Repository • Active workspace; constantly updated content (i.e faculty data sets, faculty pubs, content mapping)

21. Behavior Definitions • Atomic units: sets of standardized behaviors • Building blocks of content models • Allow for flexible reuse of data • Contributes to inter-repository sharing of objects • Dissemination of standard output: XML, plain text, binary format • Rendering/processing of disseminations is the responsibility of applications implemented over the repository.

22. Content Models • Unique content models built from content modeling components. • Digital Objects that subscribe to a given content model inherit all methods established by a particular behavior. • Digital objects can subscribe to content models that suit their type or class. • Functional not presentation specific

23. Implementation Challenges • Processing large (>10MB) XML Documents • XML databases • Processing large images • Imaging servers • Streaming Media • GIS data • Modeling Collections • Advanced Searching • “Shopping cart” searching • Caching Disseminations

24. TDL Architecture • Drop Box and Ingestion Service • Naming Service • Fedora Repository Service • Indexing and Search Service • Interfacing Services

25. Indexing Search Service • Indexing • Digital objects piped through from ingestion service • Metadata index • Full-text index • Specialized XML index • Implementation • Java indexing application • Oracle database • Supported Types of Search • Basic full-text • Basic metadata • Advanced metadata • Accessing the service • HTTP GET/POST • SOAP

26. TDL Architecture • Drop Box and Ingestion Service • Naming Service • Fedora Repository Service at Tufts • Indexing Service and Search Engine • Interfacing Services

27. Interfacing Services • An important design requirement for TDR was to allow current digital library applications to easily interface with TDR and provide access to the content in the digital repository within their own environments in a seamless fashion. • Current applications like VUE can interface with this service to allow their tools to disseminate the content that resides in TDL • The service is being designed not only to support current applications but also to accommodate the needs of future yet-to-be-defined applications like course management systems, learning tools, portals etc.

28. Fedora OKI Bridge

29. Applications Accessing TDR Content • Tufts Digital Library Application • http://dl.tufts.edu/ • Visual Understanding Environment (VUE) • http://vue.tccs.tufts.edu/

31. Future Directions • Revised search service (Zebra?) • XML database for metadata and XML objects (eXist) • Customization and enhancement to address a wide variety of needs (i.e. University Records). • Object factory: a workbench for building certain classes of objects • Automated browsing service for Repository. • Authentication and authorization modules • Asset Definitions • Collection Modeling • Federation

32. Asset Definitions • The purpose of the Fedora Asset Definition is to define and expose content types and methods of objects/assets in a repository in a standard way. The goal is to facilitate access between applications and digital repositories, digital repositories and digital repositories, etc. • Some of the questions that we asked ourselves during our repository and application development helped us form the concept of an “Asset Definition.” For example: • How can an application find out what are the objects/assets within a particular repository and how does one figure out how to refer to these objects? • If one has an object/asset in a repository, how does one describe it so that other applications can understand what they can do with it?

33. Asset Definitions, cont… getFullAssetDefintion getPreview getDescription getFullView getDefaultContent getDescMetadata getAdminMetadata getThumbnail getScreenSize getMaxSize getDynamicView

34. Collection Modeling

35. Collection Modeling • Object Relationships • Extend Fedora RDF to create collection networks • Recursive disseminators to track paths in the network • Facilitate access to sets of materials • Facilitate management of digital objects • Facilitate browsing of sets of materials • http://nikolai.tccs.tufts.edu:1980/fedora/get/demo:collectionAll/demo:Collection/viewMembers/