Fedora Repository Features

Fedora Repository Web Service Interfaces

The interface to the system consists of three open APIs that are exposed as web services:

• Management API (API-M) – defines an interface for administering the repository. It includes operations necessary for clients to create and maintain digital objects and their components. API-M is implemented as a SOAP-enabled web service.
  
  
• Access API (API-A) – defines an interface for accessing digital objects stored in the repository. It includes operations necessary for clients to perform disseminations on objects in the repository and to discover information about an object using object reflection. API-A is implemented as a SOAP-enabled web service.
  
  
• Access-Lite API (API-A-Lite) – defines a light-weight version of the Fedora Access Service that is implemented as a REST-based web service that can be invoked with a simple URL syntax.



• Management-Lite API (API-M-Lite) – this interface is under development. The intent is to provide a light-weight version of the Fedora Management Service implemented as a REST-based web service that can be invoked with a simple URL syntax. Currently, there is only one operation implemented, which is the getNextPID. A full versioin of this interface may be provided in a future release, depending on user demand.



• Search API (part of API-A-Lite) – this interface provides a simple search of the repository. The search operates upon the default index for the repository which contains object properties and the default Dublin Core record for the repository. This search interface is intended as a basic field search of the object registry. It is expected that other services will be used to created to index Fedora objects at a finer-grained level than provided by the default search.



• Resource Index Search API – this is a new interface as of Fedora 2.0 that provides searching of the new Resource Index. The Resource Index is an RDF-based index of the Fedora repository that includes the following for each digital object:
  1. object properties
  2. object-to-object relationships
  3. metadata about datastreams and disseminations
  4. default Dublin Core record

Major Features of the Fedora Repository

• Open Source - The Fedora repository system is open source software licensed under the Mozilla Public License.
  
  
• Flexible Digital Object Model - The Fedora digital object model provides the flexibility to create kinds of objects including documents, images, electronic books, multi-media learning objects, datasets, metadata, and more. Please refer to the Fedora Digital Object documentation for more details. The model a supports the aggregation of one or more content items as "Datastreams". The bytestream content of a Datastream can be any media type and can be either stored locally in the repository, or referenced by a digital object (i.e., content stored outside the repository. The Fedora object model also provides a mechanism (known as a Disseminator) for associating services with an object to produce dynamic or computed content from digital objects.
  
  
• Content Versioning - The Fedora content versioning system is enabled with the release of Fedora 1.2. Any modifications made to a Datastream or Disseminator through the Fedora management interface (API-M) will automatically result in the creation of a new version of that Datastream or Disseminator. The Fedora object contains a record of alll versions, thereby creating a history of how objects changed over time. Additionally, Fedora maintains an audit trail record of the nature of the object change events. Access to prior versions is available by adding a date-time stamp to requests on the Fedora Access service (API-A and API-A-LITE).
  
  
• XML Ingest and Export - Digital objects can be submitted to a Fedora repository as XML-encoded files that conform to either the Fedora Object XML (FOXML) schema or an extension of the Metadata Encoding and Transmission Standard (METS) schema. In future releases of Fedora other formats will be supported including MPEG2/DIDL and METS 1.3
  
  
• XML Storage - By default, Fedora digital objects are stored in a Fedora repository as XML-encoded files that conform to Fedora Object XML (FOXML) format. As previously mentioned, objects can be both ingested and exported in other XML formats. Content bytestreams that are aggregated as Datastreams in a digital object are stored in their native formats in the repository persistent storage area.
  
  
• Object-to-Object Relationships - Fedora provides the ability to assert object-to-object relationships. Object-to-Object relationship metadata is a way of asserting various kinds of relationships among Fedora objects including the notion that an object is a member of a collection, is considered a part of another object, is a derivation of another object, is a description of another object, or is equivalent to another object.. A default set of common relationships is defined in the Fedora relationship ontology, although other community or user-defined relationships may also be asserted. These relationships are automatically indexed by Fedora as part of the Fedora Resource Index.
  
  
• Access Control and Authentication - Release 1.2 includes a simple form of access control to provide access restrictions based on IP address. IP range restriction is supported in both the Management and Access APIs. In addition, the Management API is protected by HTTP Basic Authentication. In the upcoming Fedora 2.1 release we will introduce a new Access Control and Authentication module that will include the ability to enforce fine-grained access control policies expressed using XACML! (Winter/Spring 2005)
  
  
• Simple Search - Fedora automatically creates two indexes of the repository. The default search index is a simple index of the repository searchable by object properties and object Dublin Core elements. As of Fedroa 2.0 there is the new RDF-based Resource Index which includes more information about objects plus object-to-object relationships. Both of these indexes are searchable via REST-based web service interfaces.
  
  
• RDF-based Resource Index - As of Fedroa 2.0 there is the new RDF-based Resource Index which includes more information about objects plus object-to-object relationships. Both of these indexes are searchable via REST-based web service interfaces. See the Resource Index Guide for more information.
  
  
• OAI Metadata Harvesting Provider - The OAI Protocol for Metadata Harvesting is a standard for sharing metadata across repositories. Every Fedora digital object has a primary Dublin Core record that conforms to the schema at: http://www.openarchives.org/OAI/2.0/oai_dc.xsd. This metadata is accessible using the OAI Protocol for Metadata Harvesting, v2.0.
  
  
• Migration Utility - A new migration utility is provided to perform mass export and mass ingest of objects. At the core, the migration utility is built upon two newly enhanced command-line functions: fedora-export and fedora-ingest. Used together, these two command line functions can support a variety of scenarios involving moving or copying objects between repositories. The utility is general-purpose in that it can be used to copy or move objects among repositories for many reasons including upgrading from previous releases of Fedora. Client access to the migration comes in two forms: (1) run fedora-export and fedora-ingest at the command line, or (2) use the Fedora Administrator client to invoke these functions (see menu items File/Ingest and File/Export).
  
  
• Batch Utility - The Fedora repository system includes a Batch Utility as part of the Fedora Administrator client that enables the mass creation and modification of Fedora digital objects.



• Reporting Utility - A reporting utility is provided providing different management views of the contents of the Fedora repository.