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1. As a user from the Registrar office creates an Asset with a loan agreement document, the user assigns a property to the asset indicating that the asset is restricted to the Registrar staff, the user (a member of the Registrar group) should not be locked out of viewing/editing the resource.
2. A user wishes to create multiple resources that all share access restrictions. The user is able to create a single access control list that is used by that group of resources. In addition, they do not have to explicitly link to the ACL from every resource; the appropriate ACL is inferred from the collection a resource is a member of (collection defined by as a resource that ldp:contains the target resource) , or the class(es) it is an instance of. 
3. There is a collection that is by default restricted access. However, there are a selection of resources within that collection that are publicly available. These public resources are not necessarily grouped together in a single hierarchy within the collection.
4. An unauthenticated user requests a protected resource. The system presents them with an authentication challenge. The user successfully authenticates, and it is determined that they have read access to the requested resource. The system retrieves and presents the resource to the user.  
   1. Some means of simulating this scenario will have to be devised for testing purposes, since presumably the test Vagrant will not be connected to an authentication service.
5. An authorized user must be able to change which ACL applies to a given resource or group of resources without moving those resources.
6. An authorized user must be able to edit an ACL in place in order to update the policy that applies to all resources governed by that ACL.
7. An ACL should be its own ACL; thus, a user who has read (or write) access to a given ACL should be able to read (or write) to that ACL.  A user who has no access according to a given ACL should not be able to view the ACL.
8. A collection of books has an ACL that allows anonymous read access. One book within that collection (book A) has more restrictive access rules (i.e. only certain authorized users can read it), and these rules are defined in a different ACL that book A points to.  Another book in the same collection (book B) points to no ACL directly, but should be governed by the ACL of the parent collection.  When an anonymous user attempts to access book A, access should be denied (due to the ACL that book A points to), but when the same user tries to access book B, access is allowed by virtue of the ACL that the parent collection points to.  
9. The opposite scenario to #8 above – i.e. where the collection has more restrictive rules and the child book has more permissive rules – should also be possible by simply reversing the two ACLs.

Phase 2 - proposed

1. A resource can be related to tags. Each tag is contained in a tag category: Conservation, Imaging, Licensing, etc. For tags related to a certain resource:
   1. Imaging users can read, create and delete tags in Imaging category 
   2. Imaging users can read tags in Conservation category
   3. Conservation users can read, create and delete tags in Conservation and Imaging categories
   • Note: F4 does not have "tags" per se. Are you envisioning a "tag" as a resource? or a property?
   • See comment below
2. Enforce ACLs on binary resources
3. Add support for external ACL resources (resources that point to an ACL that is outside the Fedora domain)
4. Add support for external agentClass graphs
5. Enforce ACLs on ACL resources with a filesystem-based backstop (at present, only the admin user can add/edit ACLs)
6. Verify header-based (delegated) authentication use cases
7. Add ACL URIs to response headers as Link: <acl-uri>; rel=meta
8. Implement acl:Control and acl:Append modes
9. Add support for inclusion of other acls via acl:include

Removed/Amended Use Cases

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1. Given these multiple ways of inferring which ACLs apply to a given resource (via collection, class, or other metadata), there must be clear rules for determining the precedence of policies and for resolving conflicts between policies.
   1. See Finding the effective policy set below.
2. In the interest of security, the absence of an applicable ACL should result in denial of Create, Update, and Delete requests (and possibly also Read requests?) to non-admin users, but should allow all CRUD operations to admin users.
   1. the absence of an applicable ACL will result in denial of all requests.

Proposed Requirements

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(Phase 1)

Sprint 1 (Phase I) Requirements

1.  F4 F4 MUST allow assertions about authorization to be modeled in RDF in accordance with the WebAccessControl specification.
   1. Access assertions to be implemented are 
      1. READ  READ -> GET a resource
      2. WRITE  WRITE -> PUT/POST/PATCH/DELETE a resource
      3. APPEND  APPEND -> PATCH a resource, restricted to Insert statements only.
   2. as well as extending for:
      1. DELETE  DELETE -> DELETE a resource
      2. UPDATE  UPDATE -> PUT/POST a resource
   3. The  The implementation assumes an ACL is it's own ACL, therefore CONTROL will not be implemented at this time.
   4. Optional extensions (ie. regex matching) will not be implemented in Phase 1.
2. F4  F4 MUST be able to enforce authorization based on WebAC when a resource is requested via the REST-API
3. F4  F4 MUST allow authorization policies to apply to a group of resources which consists of:
   1. Resources  Resources sharing a rdf:type attribute matching an acl:accessToClass rule in an ACL in the preconfigured location.
      1. Note: sprint-1 implementation does not confine ACLs to reside in a "preconfigured location", but they can instead exist anywhere within the repository.
   2.  Resources Resources (without their own specific policy) share the policy of their container (defined by as the resource which ldp:contains the target).
4. F4  F4 MUST honor the most permissive authorization policy when multiple policies apply to a request.
   1. See the sections below on Finding the effective ACL and Resolving section Finding the effective policy from an ACLset, for more clarity.
   2. The only conflict that can arise is if two ACLs are applied with direct reference to the same resource, in these cases the most permissive policy will be applied.
5. F4  F4 MUST provide a way for external services such as Solr to enforce the authorization rules defined in the repository.
   
   1. Would one method of achieving this be to create separate solr cores for public users vs. admin users and publish only the public resources to the former and everything to the latter, or does the use case dictate more granular distinctions?
6.  Each request for a Web Resource returns an HTTP document containing a Link header (Link: <>; rel=acl) to an ACL resource which describes access to the given resource and potentially others.
7.  Servers are required to recognize the class foaf:Agent as the class of all agents (i.e. foaf:Agent is synonymous with "everyone")

Sprint 2 (Phase I) Requirements 

Must have

1. Enforce ACLs on ACL resources with filesystem-based backstop:

   1. Jira
      server DuraSpace JIRA serverId c815ca92-fd23-34c2-8fe3-956808caf8c5 key FCREPO-1792

2. Implement acl:Control, acl:Append, acl:Update and acl:Delete modes: 

   1. Jira
      server DuraSpace JIRA serverId c815ca92-fd23-34c2-8fe3-956808caf8c5 key FCREPO-1794

3. F4 MUST provide a way for external services such as Solr to enforce the authorization rules defined in the repository: 

   1. Jira
      server DuraSpace JIRA serverId c815ca92-fd23-34c2-8fe3-956808caf8c5 key FCREPO-1795

       and 

   2. Jira
      server DuraSpace JIRA serverId c815ca92-fd23-34c2-8fe3-956808caf8c5 key FCREPO-1802

4. Enforce ACLs on binary files: 

   1. Jira
      server DuraSpace JIRA serverId c815ca92-fd23-34c2-8fe3-956808caf8c5 key FCREPO-1791

5. More documentation: 

   1. Jira
      server DuraSpace JIRA serverId c815ca92-fd23-34c2-8fe3-956808caf8c5 key FCREPO-1239

   2. Jira
      server DuraSpace JIRA columns key,summary,type,created,updated,due,assignee,reporter,priority,status,resolution serverId c815ca92-fd23-34c2-8fe3-956808caf8c5 key FCREPO-1806

   3. Jira
      server DuraSpace JIRA columns key,summary,type,created,updated,due,assignee,reporter,priority,status,resolution serverId c815ca92-fd23-34c2-8fe3-956808caf8c5 key FCREPO-1791

6. Add support for agentClass graphs defined within F4: 

   1. Jira
      server DuraSpace JIRA serverId c815ca92-fd23-34c2-8fe3-956808caf8c5 key FCREPO-1793

7. Verify header-based (delegated) authentication is supported (where headers are used to define the effective agent, independent of any container-based AuthN): 

   1. Jira
      server DuraSpace JIRA serverId c815ca92-fd23-34c2-8fe3-956808caf8c5 key FCREPO-1790

8. Fix bug with versioned resources: 

   1. Jira
      server DuraSpace JIRA serverId c815ca92-fd23-34c2-8fe3-956808caf8c5 key FCREPO-1760

9. Make webac and audit default configuration in fcrepo-webapp-plus: 

   1. Jira
      server DuraSpace JIRA serverId c815ca92-fd23-34c2-8fe3-956808caf8c5 key FCREPO-1773

   2. Jira
      server DuraSpace JIRA serverId c815ca92-fd23-34c2-8fe3-956808caf8c5 key FCREPO-1821

10. Bug fixes

    1. Jira
       server DuraSpace JIRA columns key,summary,type,created,updated,due,assignee,reporter,priority,status,resolution serverId c815ca92-fd23-34c2-8fe3-956808caf8c5 key FCREPO-1809

Nice to have

1. Add ACL uris to response headers as "Link: <acl-uri>; rel=acl": 

   1. Jira
      server DuraSpace JIRA serverId c815ca92-fd23-34c2-8fe3-956808caf8c5 key FCREPO-1795

2. Support external ACLs (ACLs not managed by fedora)
3. Add support for agentClass graphs defined external to F4
4. Minor code cleanup: 

   1. Jira
      server DuraSpace JIRA columns key,summary,type,created,updated,due,assignee,reporter,priority,status,resolution serverId c815ca92-fd23-34c2-8fe3-956808caf8c5 key FCREPO-1807

Likely not

1. Support for inclusion of other ACLs via acl:include

Removed requirements

1. F4 resources that are open for public read should not challenge the client to authenticate
   1. What if a resource has no ACL? Should there be a default behavior? (for example allow all to admin user; deny all to non-admin?)
   2. This requirement specifies public *read*. Do we also want to allow a public write? While use cases for the latter are admittedly going to be rare, it would seem better not to be opinionated here if public write is what an implementer wants.

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