Pod Resources

Resource Types

ESS Pods supports storing different types of resources:

• Resource Description Framework (RDF) Resources

• Non-RDF Resources

• Containers

CRUD Operations

ESS supports the Solid Protocol specification. As such, retrieving, creating, deleting and editing Solid Resources within a Pod is directly supported via the standard HTTP interfaces.

Access Control

This section summarizes the relationship between Create/Read/Update/Delete (CRUD) operations and the required access modes.

Create

To create a resource, the user requires either an Append or Write access.

Note The creation operation creates the resource (be it container, RDF resource, non-RDF resource) and updates the content of the parent container with the new resource’s metadata.

Resource	Description
Container	Either Append or Write access on the parent container (under which the new container is to be created) allows agents to create a new container. For example, to create https://storage..../parentcontainer/newContainer/, either an Append or a Write access on https://storage..../parentcontainer/ allows agents to create https://storage..../parentcontainer/newContainer/.
RDF resource	Either Append or Write access on the parent container (under which the new resource is to be created) allows agents to create a RDF resource. For example, to create https://storage..../parentcontainer/newResource/, either an Append or a Write access on https://storage..../parentcontainer/ allows agents to create https://storage..../parentcontainer/newResource.
Non-RDF resource	Either Append or Write access on the parent container (under which the new resource is to be created) allows agents to create a new non-RDF resource. For example, to create https://storage..../parentcontainer/foo.jpg, an Append or Write access on https://storage..../parentcontainer/ allows agents to create https://storage..../parentcontainer/foo.jpg.

Read

For read operations, the user requires Read access.

Resource	Description
Container	Read access to the target container (analogous to a folder in a file system), allowing agents to read/retrieve the container as a resource (not the resource(s) under the container). That is, Read access only affects read operation on the container itself. Reading a container (which stores metadata about the resources contained within the container) allows a client to discover what resources are contained inside the container and their resource type (i.e., analogous to an ls on a folder in a file system).
RDF resource	Read access to the RDF resource allows agents to read/retrieve the resource (regardless of the access on the parent container). For example, if a resource has as its URL https://storage..../container/ResourceToRead, to read/retrieve this resource: The user must have Read access on https://storage..../container/ResourceToRead. The user’s access on https://storage..../container/ is immaterial.
Non-RDF resource	Read access on a non-RDF resource allows agents to read/retrieve the resource (regardless of Read access on the container). For example, if a non-RDF resource has as its URL https://storage..../container/foo.jpg, to read/retrieve this resource: The user must have Read access on https://storage..../container/foo.jpg. The user’s access on https://storage..../container/ is immaterial.

Read access is also required to subscribe to notifications about a resource.

Update

For update operations, the user requires Append or Write access, depending on the specific update operation.

Resource	Description
Container	To add resources to the Container, see the Create tab. To delete resources from the Container, see the Delete tab.
RDF resource	Either Append or Write access on an RDF resource allows agents to add content (statements) to the resource. Write access on an RDF resource allows agents to delete content (statements) from the resource. Write access on an RDF resource allows agents to modify existing content (statements) in the resource.
Non-RDF resource	Write access on the target resource allows agents to overwrite/replace the resource (regardless of the access on the parent container). For example, if the non-RDF resource has as its URL https://storage..../container/foo.jpg, to overwrite this resource: The user must have Write access on https://storage..../container/foo.jpg. The user’s access on https://storage..../container/ is immaterial.

Delete

For delete operations, the user requires Write access.

Resource	Description
Container	Write access to both the parent container and the target container allows agents to delete the target container. For example, to delete https://storage..../parentcontainer/containerToDelete/, Write access to both https://storage..../parentcontainer/ and https://storage..../parentcontainer/containerToDelete/ allows agents to delete https://storage..../parentcontainer/containerToDelete/ Tip To delete a container, the container must be empty.
RDF resource	To delete an RDF resource , Write access on both the parent container and the target resource allows agents to delete the target resource. For example, to deletehttps://storage..../parentcontainer/resourceToDelete/,Write access on bothhttps://storage..../parentcontainer/ andhttps://storage..../parentcontainer/resourceToDelete allows agents to deletehttps://storage..../parentcontainer/resourceToDelete.
Non-RDF resource	To delete a non-RDF resource, Write access on both the parent container and the target resource allows agents to delete the target resource. For example, to deletehttps://storage..../parentcontainer/foo.jpg, Write access on both https://storage..../parentcontainer/ and https://storage..../parentcontainer/foo.jpg allows agents to deletehttps://storage..../parentcontainer/foo.jpg.

Tip To delete a container, the container must be empty.

Other Considerations

Resource Deletion

For resource deletions, ESS uses soft deletes. That is, ESS marks the resource as deleted but does not perform an actual delete from the data store. The use of soft deletes can:

• Help maintain throughput when compared to database delete operations that may be potentially costly due to locking.

• Facilitate disaster recovery.

• Be part of a data-retention strategy.

Overwriting a resource with a new resource also results in a soft delete of the old version of the resource.

Overwriting a resource with a new resource is separate from an operation that just modifies the contents of a resource. Instead, modification of the contents (even though the modification may completely replace the contents) results in orphan data.

ESS provides the ability to schedule hard deletes for the soft deleted resources

Modification of Resource Content

When data in a file is modified or deleted, the old data remains but is no longer referenced by metadata. That is, the replaced/deleted data is orphaned.

ESS provides the ability to schedule hard deletes for the orphan data.

The modification/deletion of the data is separate from overwriting a file with a new file. Overwriting a file does not result in orphan data. Instead, overwriting a file with a new file results in a soft delete of the old version of the file.

Initial Access Policies

When a Pod is created, like any other Pod resource, an Access Control Resource is also created for the Pod Root. The ACR is initialized with the default ACP policies for the Pod Owner and for Access Grant enablement:

• Initial Pod Owner policies give the Pod Owner read and write access to the Pod. These policies also specify a client matcher as well if the Authorization service’s configuration for the initial client allow list is set:

  • INRUPT_AUTHORIZATION_DEFAULT_ACR_CLIENT_ID_ALLOW_LIST or if that is unset,

  • INRUPT_AUTHORIZATION_CLIENT_ID_ALLOW_LIST

Allow List is Set

ESS uses the values in its Authorization service’s INRUPT_AUTHORIZATION_DEFAULT_ACR_CLIENT_ID_ALLOW_LIST (at the time of Pod creation) to create the client matcher for the initial ACP policies. If the configuration is unset, ESS uses the values in its Authorization service’s INRUPT_AUTHORIZATION_CLIENT_ID_ALLOW_LIST (at the time of Pod creation).

Using the value of the Pod owner’s WebID and an initial client allow list, ESS creates the initial policies of the form:

If allOf(AgentMatcher and ClientMatcher) evaluates to true, Then allow (Read and Write).

Specifically, ESS creates:

Policy 1 for the Pod Root: If the agent matches the Pod owner’s WebID, and if the client application’s Client ID has a match in the initial client allow list, allow Read and Write access.

Policy 2 for the Pod Root’s Initial Member Policies: If the agent matches the Pod owner’s WebID, and if the client application’s Client ID has a match in the initial client allow list, allow Read and Write access.

For more information on a Container’s Member Policies, see Member Policies.

Allow List is Not Set

ESS uses the values in its Authorization service’s INRUPT_AUTHORIZATION_DEFAULT_ACR_CLIENT_ID_ALLOW_LIST (at the time of Pod creation) to create the client matcher for the initial ACP policies. If the configuration is unset, ESS uses the values in its Authorization service’s INRUPT_AUTHORIZATION_CLIENT_ID_ALLOW_LIST (at the time of Pod creation).

If the initial client allow list is empty (when creating the policy), ESS uses the value of the Pod owner’s WebID to create initial policies of the form:

If allOf(AgentMatcher) evaluates to true, Then allow (Read and Write).

Specifically, ESS creates:

Policy 1 for the Pod Root: If the agent matches the Pod owner’s WebID, allow Read and Write access.

Policy 2 for the Pod Root’s Initial Member Policies: If the agent matches the Pod owner’s WebID, allow Read and Write access.

For more information on a Container’s Member Policies, see Member Policies.

Disambiguation Both Authorization Service and Pod Storage Service have a INRUPT_AUTHORIZATION_CLIENT_ID_ALLOW_LIST setting.

Only the Authorization Service setting affects which clients are allowed. The Pod Storage Service is for Discovery purposes only.

• Initial Access Grant Enablement policies allow the use of Access Grants that grant read/write/append access to the Pod resources.

  If allOf(VC Matcher) evaluates to true, Then allow (Read and Write and Append).

  Specifically, ESS creates: Policy 3 for the Pod Root: If a presented VC matches the specified type, allow its use for Read, Write, and Append access. Policy 4 for the Pod Root’s Initial Member Policies: If a presented VC matches the specified type, allow its use for Read, Write, and Append access. See also INRUPT_AUTHORIZATION_DEFAULT_ACR_ACCESS_GRANTS_ALLOWED_MODES.

Important The policies only enable the use of Access Grants for the allowed access modes. To determine the access for an agent using an access grant, ESS uses the intersection of:

• The allowed access specified by the policy, and

• The granted access specified in the Access Grant (for the resource specified in the Access Grant).

Note A Pod’s initial Policies are set when the Pod is provisioned. As such, updates to the various INRUPT_AUTHORIZATION_DEFAULT_ACR_* options do not affect existing Pods.

That is, once a Pod’s initial policies have been created, changes to the various INRUPT_AUTHORIZATION_DEFAULT_ACR_* options are not reflected in that Pod’s policies.