Pod Resources
Resource Types
ESS Pods supports storing different types of resources:
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.
To create a resource, the user requires either an Append or Write access.
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/.
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.
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.
For read operations, the user requires Read access.
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).
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
Readaccess onhttps://storage..../container/ResourceToRead.The user’s access on
https://storage..../container/is immaterial.
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
Readaccess onhttps://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.
For update operations, the user requires Append or Write access, depending on the specific update operation.
To add resources to the Container, see the Create tab.
To delete resources from the Container, see the Delete tab.
Either
AppendorWriteaccess on an RDF resource allows agents to add content (statements) to the resource.Writeaccess on an RDF resource allows agents to delete content (statements) from the resource.Writeaccess on an RDF resource allows agents to modify existing content (statements) in the 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
Writeaccess onhttps://storage..../container/foo.jpg.The user’s access on
https://storage..../container/is immaterial.
For delete operations, the user requires Write access.
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.
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.
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.
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.
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_LISTor if that is unset,
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.
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).
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