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1. Minimize change to the user via the API
2. Retain URLs of migrated Fedora resources
3. Compliance with OCFL
4. Do not allow OCFL-isms from bleeding into Fedora API
5. Rebuildability
6. Performance
7. Reduce complexity of implementation

Issues being addressed

Based on feedback from users of Fedora 4 and 5, the design for the next major release of Fedora will address the following issues:

Preservation persistence

The notions of "completeness" and "transparency" are important when it comes to how a preservation repository persists its resources (metadata and binaries) to storage. The resources in storage should be "complete" in the sense that Fedora should be able to rebuild its indexes based on what is stored on disk as files. The documented transparency of those persisted files also allows for other applications to consume those resources. See section below: OCFL Persistence.

Query service

The ability to query Fedora for basic information regarding the contents of the repository has been a missing feature in Fedora 4 and 5. This design will include a simple query service for inspecting all of the Fedora resources or resources based on specific attributes. See section below: Query service.

OCFL persistence

Architecture

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1. Requirements:
   1. Check fixity of binary resource(s) by comparing computed value with stored value
   2. Check fixity of binary resource(s) given a specific set of Fedora object rdf:types
   3. Persist results of fixity check
      1. In log file?
      2. In database?
      3. In Fedora?
2. Scheduled fixity service:
   1. Probably not part of the core
   2. Run as a separate service (see: Riprap)
   3. Potentially implemented as a circular queue of Fedora resources, ordered by "last fixity check" date property on Fedora resource
3. Retain "fedora:hasFixityService" triple or header
4. At the OCFL-level, interest in providing fixity over an OCFL storage hierarchy

Query service

1. Proposal: Query service / endpoint should support the following queries:
   1. List all resources
   2. List resources by mimetype
   3. List resources by parent
   4. List resources by mimetype, parent, and modified date (<>=)
   5. List resources where modified  <> x date
2. Open questions around scope of resources to be searchable
   1. Fedora resources?
   2. Resources defined in RDF documents within the repository?
   3. Hash URIs?
3. Open questions around properties to support
   1. Server-managed triples?
   2. All properties?
4. Triplestore not necessarily required

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