| Authorize Access Model | A node access model under which an entity can subscribe only through having a subscription request approved by a node owner (subscription requests are accepted but only provisionally) and only subscribers may retrieve items. | |
| Address | (1) A JID as defined in &xmppcore;, or (2) the combination of a JID and a &xep0030; node. | |
| Collection Node | A type of node that contains nodes and/or other collections but no published items. Collections make it possible to represent hierarchial node structures. | |
| Collection Node | A type of node that contains nodes and/or other collections but no published items. Collections make it possible to represent more sophisticated relationships among nodes. Collection nodes are defined in &xep0248;. | |
| Entity | A JID-addressable Jabber entity (client, service, application, etc.). | |
| Event | A change in the state of a node. | |
| Instant Node | A node whose NodeID is automatically generated by a pubsub service. | |
| Collection | -A node that contains nodes and/or other collections but no published items. Collections make it possible to represent hierarchial node structures. | +A node that contains nodes and/or other collections but no published items. Collections make it possible to represent more sophisticated relationships among nodes. For details, refer to XEP-0248. |
These error cases are described more fully in the following sections.
When requesting subscription options, the subscriber MUST specify the JID that is subscribed to the node and SHOULD specify a node (if no node is specified, the service MUST assume that the requesting entity wishes to request subscription options for its subscription to the root collection node; see the Root Collection Node section of this document for details).
+When requesting subscription options, the subscriber MUST specify the JID that is subscribed to the node and SHOULD specify a node (if no node is specified, the service MUST assume that the requesting entity wishes to request subscription options for its subscription to the root collection node; refer to XEP-0248 for details).
The service MUST validate that the entity making the request is authorized to set the subscription options for the subscribed entity. If the subscriber's JID is of the form &FULLJID;, a service MUST perform this check by comparing the &BAREJID; part of the two JIDs to ensure that they match. If the bare JID portions of the JIDs do not match and the requesting entity is not authorized to modify subscription options for the JID (e.g., because it is not a service-wide admin or authorized proxy), the service MUST return a &forbidden; error.
If the service or node does not support item retrieval (e.g., because the node is a collection node), the service MUST return a &feature; error to the subscriber, specifying a pubsub-specific error condition of <unsupported/> and a feature of "retrieve-items".
+If the service or node does not support item retrieval (e.g., because the node is a collection node as described in XEP-0248), the service MUST return a &feature; error to the subscriber, specifying a pubsub-specific error condition of <unsupported/> and a feature of "retrieve-items".
If the node does not support item publication (because it is a Collection Node), the service MUST return a &feature; error, specifying a pubsub-specific error condition of <unsupported/> and a feature of "publish".
+If the node does not support item publication (e.g., because it is a collection node as described in XEP-0248), the service MUST return a &feature; error, specifying a pubsub-specific error condition of <unsupported/> and a feature of "publish".
Note: When a service successfully creates a node on behalf of the requesting entity, it MUST return an IQ result. If the node creation request did not specify a NodeID and the service supports creation of instant nodes, the service MUST specify the created NodeID in the IQ result. Similarly, if the node creation request specified a NodeID but the service modified the NodeID before creating the node as described in the Collection Nodes section of this document, the service MUST also specify the modified node in the IQ result. In all other cases, the service MUST NOT specify the NodeID in the IQ result (since the node creator can determine which node was created by tracking the 'id' attribute that it specified for the IQ-set).
+Note: When a service successfully creates a node on behalf of the requesting entity, it MUST return an IQ result. If the node creation request did not specify a NodeID and the service supports creation of instant nodes, the service MUST specify the created NodeID in the IQ result. Similarly, if the node creation request specified a NodeID but the service modified the NodeID before creating the node (refer to XEP-0248), the service MUST also specify the modified node in the IQ result. In all other cases, the service MUST NOT specify the NodeID in the IQ result (since the node creator can determine which node was created by tracking the 'id' attribute that it specified for the IQ-set).
As explained above, each node type has its own default configuration. By asking the service to create a node with default configuration, the node creator accepts the default configuration. If the service allows node configuration, the owner may reconfigure the node after creating the node (as described in the Configure a Node section of this document). In addition, a service MAY allow entities to determine the default configuration options for a given node type before creating a node (as described in the Request Default Configurations section of this document).
@@ -3257,7 +3254,7 @@ And by opposing end them? ]]> -(For error handling if the service does not support the specified node type, see the Collection Node section of this document.)
+(For error handling if the service does not support the specified node type, refer to XEP-0248.)
If an implementation allows node configuration (see the Configure a Node section of this document), it SHOULD allow node creation requests to contain the desired node configuration in the node creation request.
@@ -3595,7 +3592,7 @@ And by opposing end them? ]]>If the "pubsub#notify_config" option is set to true, the service MUST send a notification of configuration change to all subscribers. (A service SHOULD support this option for leaf nodes and MUST support it for Collection Nodes.) If the node configuration is set to event notifications only, the notification MUST consist of an empty <configuration/> element whose 'node' attribute is set to the NodeID of the node; if the node configuration is set to full payloads, the <configuration/> element MUST in addition contain the node configuration as represented via the Data Forms protocol.
+If the "pubsub#notify_config" option is set to true, the service MUST send a notification of configuration change to all subscribers. (A service SHOULD support this option for leaf nodes and MUST support it for collection nodes as described in XEP-0248.) If the node configuration is set to event notifications only, the notification MUST consist of an empty <configuration/> element whose 'node' attribute is set to the NodeID of the node; if the node configuration is set to full payloads, the <configuration/> element MUST in addition contain the node configuration as represented via the Data Forms protocol.
The default configuration options may be different for a collection node vs. a leaf node. In order to specifically request the default configuration options for collection nodes, an entity MUST include a Data Form with a 'pubsub#node_type' field whose value is "collection" in the request (since the default value for the 'pubsub#node_type' field is "leaf").
-If the service does not support collection nodes, it MUST return a &feature; error, specifying a pubsub-specific error condition of <unsupported/> and a feature of "collections".
-If a service supports node creation, it MUST support node deletion. If an implementation persists items, it MUST remove all items from persistent storage before the node itself is deleted.
@@ -3872,13 +3827,12 @@ And by opposing end them? ]]> -If the node to be deleted is a collection node, the service should follow the recommendations provided under Collection Node Deletion.
There are several reasons why the node deletion request might fail:
These error cases are described more fully in the following sections.
@@ -3895,22 +3849,6 @@ And by opposing end them?If the requesting entity attempts to delete the root collection node, the service MUST return a ¬allowed; error.
-If the service or node does not persist items (e.g., because the node is a collection node), it MUST return a &feature; error, specifying a pubsub-specific error condition of <unsupported/> and a feature of "persistent-items".
+If the service or node does not persist items (e.g., because the node is a collection node as described in XEP-0248), it MUST return a &feature; error, specifying a pubsub-specific error condition of <unsupported/> and a feature of "persistent-items".
In order to deny the request, the owner shall submit the form and set the "pubsub#allow" field to a value of "0" or "false"; as above, the message MUST reflect the 'id' attribute originally provided.
@@ -4783,678 +4721,6 @@ And by opposing end them?A pubsub service MAY support collection nodes as well as leaf nodes. Collections enable nodes to be grouped together in many ways. A collection node MUST contain only leaf nodes and/or other collection nodes (similar to the way in which a file system directory can contain both files and subdirectories) and MUST NOT contain published items (therefore a collection MUST NOT support the "publish" feature or related features such as "persistent-items"). If collections are supported, a service MUST advertise that fact in its "disco#info" responses by including a feature of "pubsub#collections" and MUST support service discovery of child nodes as described in the Discover Nodes section of this document.
- -This section provides background information about collection nodes, with insights from graph theory.
In terms of graph theory, the set of nodes hosted at a pubsub service is a directed acyclic graph.
Finally, in XMPP pubsub, all graphs are oriented because any two collection nodes cannot have a bidirectional relationship (i.e., if collection node #1 is a direct predecessor of collection node #2 then #2 cannot also be a direct predecessor of #1).
-This terminology is summarized in the following table.
-| Model | -Description | -Root Node | -Multiple Parents | -Node Dependency | -Depth | -
|---|---|---|---|---|---|
| Flat Set | -A set of nodes with no parent-child relationships (i.e., there are no collection nodes). | -No | -N/A | -No | -0 (zero) | -
| Directed Acyclic Graph (DAG) | -A set of nodes with parent-child relationships, where a child node can have more than one parent. | -Yes | -Yes | -No | -1 or infinite | -
| Dag Set | -A set of DAGs with no root node. | -No | -Yes | -No | -1 or infinite | -
| Tree | -A set of nodes with parent-child relationships, where a node can be the child of only one parent. | -Yes | -No | -No | -1 or infinite | -
| Forest | -A set of trees with no root node. | -No | -No | -No | -1 or infinite | -
| Strict Hierarchy | -An infinite tree in which a child node can have only one parent and is dependent on its parent. | -Yes | -No | -Yes | -Infinite | -
| Strict Hierarchy Set | -A set of strict hierarchies with no root node. | -No | -No | -Yes | -Infinite | -
| Loose Hierarchy | -An infinite DAG in which a child node can have multiple parents but cannot exist without at least one parent. | -Yes | -Yes | -Yes | -Infinite | -
| Loose Hierarchy Set | -A set of loose hierarchies with no root node. | -No | -Yes | -Yes | -Infinite | -
A service that implements collection nodes SHOULD allow entities to subscribe to collection nodes (subject to access models and local security policies).
-In addition to the subscription configuration options already defined, there are two subscription configuration options specific to collection nodes:
-pubsub#subscription_type
-This subscription option enables the subscriber to subscribe either to items or to nodes.
-If the subscription type is "items", the subscriber shall be notified whenever any node contained in the collection generates a notification (e.g., when an item is published or deleted), as modified by the value of the "pubsub#subscription_depth" option.
-If the subscription type is "nodes", the subscriber shall be notified whenever a new node is added to the collection, as modified by the value of the "pubsub#subscription_depth" option.
-The default value of this subscription option MUST be "nodes".
-pubsub#subscription_depth
-This subscription option enables the subscriber to specify whether it wants to receive notifications only from first-level children of the collection (a value of "1") or from all descendents (a value of "all").
-For subscriptions of type "items", this enables the subscriber to be informed only when an item is published to a leaf node that is a direct child of the collection node to which it has subscribed, or to be informed whenever an item is published to any leaf node in the "tree" that begins at the level of the collection to which it has subscribed.
-For subscriptions of type "nodes", this enables the subscriber to be informed only when a new node is added in the specific collection to which it has subscribed, or to be informed whenever a node is added anywhere in the "tree" that begins at the level of the collection to which it has subscribed.
-The default value of this subscription option MUST be "1".
-In order to subscribe to a collection node, an entity MUST send a subscription request to the node; the subscription request MAY include subscription options, but this is not strictly necessary (especially if the entity does not wish to override the default settings for the "pubsub#subscription_type" and "pubsub#subscription_depth" options).
-The subscriber will now receive notification of new first-level nodes created within the "blogs" collection.
-The subscriber will now receive item notifications from nodes at any depth within the "blogs" collection.
-Depending on the nature of the node "tree", a subscription type of "items" and depth of "all" may result in an extremely large number of notifications. Therefore, a service MAY disallow such a combination of subscription options, in which case it MUST return a ¬allowed; error to the requesting entity.
-A service MAY allow an entity to subscribe to a collection node in two ways, once with a subscription of type "nodes" (to receive notification of any new nodes added to the collection or the entire tree) and once with a subscription of type "items" (to receive all items published within the tree). However, a service SHOULD NOT allow an entity to subscribe twice to a collection node (once with a subscription depth of "1" and once with a subscription depth of "all") for the same subscription type, since two such subscriptions are unnecessary (a depth of "all" includes by definition a depth of "1"); in this case the service SHOULD return a &conflict; error to the requesting entity.
-A service that implements collections SHOULD support a root collection. The root collection shall be identified by the lack of a node identifier (i.e., the address of the pubsub service itself, such as "pubsub.shakespeare.lit").
-Subscribing to this node with a subscription of type "nodes" and a depth of "1" enables an entity to be notified whenever a new first-level node is created at the pubsub service. Subscribing to this node with a subscription of type "nodes" and a depth of "all" enables an entity to be notified whenever a new node is created anywhere at the pubsub service.
-If the root collection node is configured to send notification of node associations and disassociations, the service shall send an event that contains a <collection/> element whose 'node' attribute specifies the NodeID of the collection (in this case the NodeID is empty to signify that the collection is the root collection); this element in turn contains an <associate/> element whose 'node' attribute specifies the NodeID of node that has been associated with the collection.
-The notification event MAY also include the node meta-data, formatted using the Data Forms protocol.
-To create a new collection node, the requesting entity MUST include a Data Form containing a 'pubsub#node_type' field whose <value/> is "collection".
-In addition to the errors already defined for leaf node creation, there are several reasons why the collection node creation request might fail:
-These error cases are described more fully in the following sections.
-If the service does not support collection nodes, it MUST respond with a &feature; error, specifying a pubsub-specific error condition of <unsupported/> and a feature of "collections".
-If the service supports collection nodes but does not allow new collection nodes to be created, it MUST respond with a ¬allowed; error.
-If the requesting entity has insufficient privileges to create new collections, the service MUST respond with a &forbidden; error.
-A service MAY offer some node configuration options that are specific to collection nodes and not provided in configuration forms related to leaf nodes. The following are RECOMMENDED:
-To create a new node and associate it with an existing collection, the node configuration protocol MUST be used in the node creation request (see the Create and Configure a Node section of this document). In order to specify the associated collection(s), the form MUST include a 'pubsub#collection' field.
-Note: Inclusion of the node configuration form is not necessary if the node is being created as a first-level child of the root collection node, since every such child is automatically affiliated with the root collection node (if any).
-Note: For the protocol used to associate an existing node with a collection, refer to the Associate an Existing Node with a Collection section of this document.
-Note: If the node is a collection node and the requesting entity wishes to request the default configuration, the requesting entity MUST include only the "pubsub#collection" and "pubsub#node_type" fields in the configuration form.
-If no error occurs, the service MUST create the node and associate it with the collection.
-There are several reasons why the request might fail:
-These error cases are described more fully in the following sections.
-An implementation MAY allow a node to be associated with more than one collection node and therefore MAY specify a type of "text-multi" for the "pubsub#collection" field. However, in order to reduce the complexity of implementation, it is RECOMMENDED to allow only one parent collection node for each node and therefore it is RECOMMENDED to specify a type of "text-single" for the "pubsub#collection" field. If a service supports associating a node with multiple collections, it MUST advertise support for the "multi-collection" feature (if that feature is not advertised, entities SHOULD assume that the service allows a node to be associated with only one collection). If the request specifies more than one collection node but the service allows a node to be associated with only one collection node, the service MUST return a &badrequest; error.
-If the requesting entity does not have sufficient privileges to associate a node with the specified collection node, the service MUST return a &forbidden; error.
-If no additional nodes can be associated with the collection node because a configurable limit of associated nodes has been reached, the service MUST return a &conflict; error, which SHOULD also include a pubsub-specific error condition of <max-nodes-exceeded/>.
-If the specified collection node is actually a leaf node, the service MUST return an ¬allowed; error.
-If the specified collection node does not exist, the service MUST return an ¬found; error.
-Deletion of a collection node can introduce a large number of changes to the system, depending on the node relationship model of the deployed system. This section describes recommended handling of deletion requests in the context of collection nodes.
-When the graph of the pubsub system is a Directed Acyclic Graph, a child node can have more than one parent, which may be the root collection node. Therefore, when a node owner deletes a collection node the service MUST behave as follows:
-When the graph of the pubsub system is a Dag Set, a child node can have more than one parent but there is no root collection node. Therefore, when a node owner deletes a collection node the service MUST behave as follows:
-When the graph of the pubsub system is a Tree, a child node can have only one parent, which may be the root collection node. Therefore, when a node owner deletes a collection node the service MUST behave as follows:
-When the graph of the pubsub system is a Forest, a child node can have only one parent but there is no root collection node. Therefore, when a node owner deletes a collection node the service MUST behave as follows:
-When the graph of the pubsub system is a Strict Hierarchy or a Strict Hierarchy Set, a child node can have only one parent node and cannot exist without its parent. Therefore, when a node owner deletes a collection node the service MUST behave as follows:
-Note: This action may introduce cascading changes, since deletion of a child will result in deletion of any grandchildren, great-grandchildren, etc. A service MAY refuse to allow deletion of a collection node if doing so will result in an excessive load on the system. If it so refuses, it MUST return a &constraint; error.
-When the graph of the pubsub system is a Loose Hierarchy or a Loose Hierarchy Set, a child node can have multiple parent nodes but a child node cannot exist without at least one parent node. Therefore, when a node owner deletes a collection node the service MUST behave as follows:
-Note: This action may introduce cascading changes, since deletion of a child will result in deletion of any grandchildren, great-grandchildren, etc. A service MAY refuse to allow deletion of a collection node if doing so will result in an excessive load on the system. If it so refuses, it MUST return a &constraint; error.
-Although a node can be associated with a collection when it is created (as described above), it can also be associated with a collection after it has been created. This can be done in two ways:
-These methods are described below.
-In order to modify the (child) node's "pubsub#collection" configuration field, the owner of the node shall submit a request to edit the node's configuration, receive a configuration form from the service, and then submit a modified configuration form:
-Note: To associate a node with the root collection node, the node owner MUST submit an empty <value/> element within the 'pubsub#collection' field.
-In order to modify the (parent) node's "pubsub#children" configuration field, the owner of the node shall submit a request to edit the node's configuration, receive a configuration form from the service, and then submit a modified configuration form:
-If the collection node is configured to send notification of node associations and disassociations, the service shall send an event that contains a <collection/> element whose 'node' attribute specifies the NodeID of the collection; this element in turn contains an <associate/> element whose 'node' attribute specifies the NodeID of node that has been associated with the collection.
-If an entity attempts to associate a node with a collection in a way that would violate the node relationship model (e.g., adding a second parent to a node in a Tree or Strict Hierarchy or making a child a new parent of its existing parent or other predecessor and thus violating the orientation of the graph), the service MUST return a &conflict; error.
-A node can be disassociated from a collection after it has been associated (whether at creation time or afterward). This can be done in two ways:
-These methods are described below.
-In order to modify the (child) node's "pubsub#collection" configuration field, the owner of the node shall submit a request to edit the node's configuration, receive a configuration form from the service, and then submit a modified configuration form:
-Note: To disassociate the node from all collection nodes, the node owner MUST submit an empty <field/> element for the 'pubsub#collection' field as shown in the foregoing example.
-Note: To disassociate the node from the root collection node, the node owner MUST submit an empty <value/> element within the 'pubsub#collection' field as shown in the foregoing example.
-In order to modify the (parent) node's "pubsub#children" configuration field, the owner of the node shall submit a request to edit the node's configuration, receive a configuration form from the service, and then submit a modified configuration form:
-If the collection node is configured to send notification of node associations and disassociations, the service shall send an event that contains a <collection/> element whose 'node' attribute specifies the NodeID of the collection; this element in turn contains a <disassociate/> element whose 'node' attribute specifies the NodeID of node that has been disassociated from the collection.
-If a node is disassociated from a collection node and a new association is not formed, the implementation MAY associate the node with the root collection node or associate it with no collection node.
-Note: The combination of associating a node with one collection and disassociating the same node from another collection can be used to move a node from one collection to another.
-If an item is published to a node which is also included by a collection, and an entity is subscribed to that collection with a subscription type of "items", then the notifications generated by the service MUST contain additional information. The &ITEMS; element contained in the notification message MUST specify the node identifier of the node that generated the notification (not the collection) and the &ITEM; element MUST contain a SHIM header that specifies the node identifier of the collection.
-Note: The delivery options (such as "pubsub#deliver_payloads") are determined by the publishing leaf node, not by the aggregating collection node. If the owner of a collection node sets delivery options for a collection node, the service SHOULD ignore those options and apply the options set for the leaf node that publishes an item.
-Publish-subscribe functionality can be integrated into existing instant messaging and presence services (see RFC 3921), such that each registered account functions as a virtual pubsub service (sometimes called "pubsub-on-a-JID"). In such deployments, the root pubsub node for each virtual pubsub service has the same address as the bare JID &BAREJID; of the account, which is typically associated with an IM user (e.g., <hamlet@denmark.lit>). Since an IM user typically has a roster of "buddies" and shares presence information with those buddies, the virtual pubsub service can use roster and presence information to provide some helpful shortcuts for subscribers, in particular the auto-subscribe and filtered-notifications features described in this section.
Note: Because the account owner's bare JID functions as a virtual pubsub service, it is OPTIONAL for the owner to include a 'to' address when sending publish requests and completing other publisher and owner use cases. That is, when the IM server receives a pubsub-related IQ stanza of type "get" or "set" from one of the account owner's resources, the server MUST consider the stanza to be addressed to the account owner's bare JID even if the IQ stanza does not include a 'to' address.
@@ -5619,8 +4885,8 @@ And by opposing end them?NodeIDs MAY have semantic meaning in particular profiles, implementations, or deployments of pubsub. However, it is STRONGLY RECOMMENDED that such semantic meaning not be used to encapsulate the hierarchical structure of nodes; instead, node hierarchy SHOULD be encapsulated using collections and their associated child nodes.
+NodeIDs MAY have semantic meaning in particular profiles, implementations, or deployments of pubsub. However, it is STRONGLY RECOMMENDED that such semantic meaning not be used to encapsulate the hierarchical structure of nodes; instead, node hierarchy SHOULD be encapsulated using collections and their associated child nodes as described in XEP-0248.
The SHIM headers are generated by the node to which the subscriber has a subscription, which may be either a leaf node or a collection node.
+The SHIM headers are generated by the node to which the subscriber has a subscription, which may be either a leaf node or a collection node (refer to XEP-0248).
SHIM headers are not to be included when the content does not differ based on subscription ID, e.g., when a node sends notification of a configuration change to the node itself, notification that the node has been purged, or notification that the node has been deleted.
| collection | -A pubsub node of the "collection" type. | +A pubsub node of the "collection" type as described in XEP-0248. |
| leaf | -A pubsub node of the "leaf" type. | +A pubsub node of the "leaf" type as described in XEP-0060. |
| service | @@ -6392,7 +5658,7 @@ O, what a rogue and peasant slave am I!