XEP-0099: IQ Query Action Protocol

2.1 Description¶

The existing XMPP core protocol defines four <iq/> types (get, set, result, and error). Unfortunately, these four types don't include a 'delete' type, and the 'set' type must do double duty for 'create' and 'update'. Many protocols can benefit from a clear separation of create and update paralleling other query languages such as SQL.

Protocols complying with the <query/> action protocol use <iq/> 'set' to initiate all request-response interactions. The particular action to be taken MUST be set as an "action" attribute in the <iq/> <query/> sub-element. The action attribute MUST have a value of 'create', 'read', 'update', or 'delete'. Responses use the standard <iq/> 'result' and 'error' types. For backward compatibility, an <iq/> 'get' query is treated as equivalent to an <iq/> 'set' query with action of 'read'. Action protocols may require all or just a subset of these actions depending on the desired outcome.

In addition to the action attribute an optional "strict" attribute may be set in the <iq/> <query/> sub-element. The only valid values for strict is "true" or "false" (case sensitive). The strict behavior of actions causes more errors to be returned which tends to make protocols more robust but also more complex. Action protocols MUST define the default value of the "strict" attribute in the context of that protocol. In addition, some protocols may not wish to allow changing the strict default, so action protocols MUST declare whether the strict behavior of the protocol may be set in the <iq/> <query/> sub-element.

2.2 Actions¶

2.3 Elements¶

The root element is query which is in a namespace defining the protocol in use. The query element MUST have an attribute named 'action' with values given in the previous table.

2.4 Error Codes¶

The following error codes apply to all action codes.

3.1 Description¶

The create action inserts new data on the recipient node. If the strict attribute is 'true' the create action fails if colliding data already exists on the recipient node. If the strict attribute is false, the create action will insert new data on the recipient node overwriting existing colliding data if it exists (e.g. equivalent to update).

3.2 Error Codes¶

3.3 Examples¶

Creating new data on the server using iq:private, and strict actions when no existing data is on the server.

SENDER:
<iq type="set" id="1001">
  <query xmlns="jabber:iq:private" action="create" strict="true">
    <exodus xmlns="exodus:prefs">
      <defaultnick>Hamlet</defaultnick>
    </exodus>
  </query>
</iq>

RECIPIENT:
<iq
    type="result"
    from="hamlet@shakespeare.lit/denmark"
    to="hamlet@shakespeare.lit/denmark"
    id="1001"/>

With strict actions enabled, conflict data will cause the create action to fail when existing data is on the recipient node. Here we show iq:private, and strict actions with existing data on the server.

SENDER:
<iq type="set" id="1002">
  <query xmlns="jabber:iq:private" action="create" strict="true">
    <exodus xmlns="exodus:prefs">
      <defaultnick>Hamlet</defaultnick>
    </exodus>
  </query>
</iq>

RECIPIENT:
<iq
    type="error"
    from="hamlet@shakespeare.lit/denmark"
    to="hamlet@shakespeare.lit/denmark"
    id="1002">
    <error code="409">Conflict</error>
    <exodus xmlns="exodus:prefs">
      <defaultnick>Hamlet</defaultnick>
    </exodus>
  </query>
</iq>

4.1 Description¶

The read action retrieves data on the recipient node. If the strict attribute is 'true' the read action fails if no appropriate data exists on the recipient node. If the strict attribute is false, the read action will always return with a 'result', sending an empty result in place of a 'not found' error.

4.2 Error Codes¶

4.3 Examples¶

Reading data on the server using iq:private, and strict actions when data is on the server.

SENDER:
<iq type="set" id="1001">
  <query xmlns="jabber:iq:private" action="read" strict="true">
    <exodus xmlns="exodus:prefs"/>
      <defaultnick>Hamlet</defaultnick>
    </exodus>
  </query>
</iq>

RECIPIENT:
<iq
    type="result"
    from="hamlet@shakespeare.lit/denmark"
    to="hamlet@shakespeare.lit/denmark"
    id="1001">
  <query xmlns="jabber:iq:private" action="read" strict="true">
    <exodus xmlns="exodus:prefs"/>
      <defaultnick>Hamlet</defaultnick>
    </exodus>
  </query>
</iq>

With strict actions enabled, the absence of matching data will cause the read action to fail. Here we show iq:private, and strict actions with no matching data on the server.

SENDER:
<iq type="set" id="1002">
  <query xmlns="jabber:iq:private" action="read" strict="true">
    <data xmlns="imaginary"/>
  </query>
</iq>

RECIPIENT:
<iq
    type="error"
    from="hamlet@shakespeare.lit/denmark"
    to="hamlet@shakespeare.lit/denmark"
    id="1002">
    <error code="404">Not Found</error>
    <data xmlns="imaginary"/>
  </query>
</iq>

With strict actions disabled, the absence of matching data will cause the read action to return an 'empty' result. Here we show iq:private, and strict actions disabled with no matching data on the server.

SENDER:
<iq type="set" id="1003">
  <query xmlns="jabber:iq:private" action="read" strict="false">
    <data xmlns="imaginary"/>
  </query>
</iq>

RECIPIENT:
<iq
    type="result"
    from="hamlet@shakespeare.lit/denmark"
    to="hamlet@shakespeare.lit/denmark"
    id="1003">
    <data xmlns="imaginary"/>
  </query>
</iq>

5.1 Description¶

The update action edits existing data on the recipient node. If the strict attribute is 'true' the update action fails if matching data does not already exists on the recipient node. If the strict attribute is false, the update action will edit existing data, inserting the data on the recipient node if necessary.

5.2 Error Codes¶

5.3 Examples¶

Updating existing new data on the server using iq:private, and strict actions when existing data is on the server.

SENDER:
<iq type="set" id="1001">
  <query xmlns="jabber:iq:private" action="update" strict="true">
    <exodus xmlns="exodus:prefs">
      <defaultnick>Hamlet</defaultnick>
    </exodus>
  </query>
</iq>

RECIPIENT:
<iq
    type="result"
    from="hamlet@shakespeare.lit/denmark"
    to="hamlet@shakespeare.lit/denmark"
    id="1001"/>

With strict actions enabled, the absence of existing data will cause the update action to fail. Here we show iq:private, and strict actions with no existing data on the server.

SENDER:
<iq type="set" id="1002">
  <query xmlns="jabber:iq:private" action="update" strict="true">
    <exodus xmlns="exodus:prefs">
      <defaultnick>Hamlet</defaultnick>
    </exodus>
  </query>
</iq>

RECIPIENT:
<iq
    type="error"
    from="hamlet@shakespeare.lit/denmark"
    to="hamlet@shakespeare.lit/denmark"
    id="1002">
    <error code="404">Not Found</error>
    <exodus xmlns="exodus:prefs">
      <defaultnick>Hamlet</defaultnick>
    </exodus>
  </query>
</iq>

6.1 Description¶

The delete action deletes existing data on the recipient node. If the strict attribute is 'true' the delete action fails if matching data does not already exists on the recipient node. If the strict attribute is false, the delete action will delete any existing data on the recipient node (if any) and return successful..

6.2 Error Codes¶

6.3 Examples¶

Deleting existing new data on the server using iq:private, and strict actions when existing data is on the server.

SENDER:
<iq type="set" id="1001">
  <query xmlns="jabber:iq:private" action="delete" strict="true">
    <exodus xmlns="exodus:prefs"/>
  </query>
</iq>

RECIPIENT:
<iq
    type="result"
    from="hamlet@shakespeare.lit/denmark"
    to="hamlet@shakespeare.lit/denmark"
    id="1001"/>

With strict actions enabled, the absence of existing data will cause the delete action to fail. Here we show iq:private, and strict actions with no existing data on the server.

SENDER:
<iq type="set" id="1002">
  <query xmlns="jabber:iq:private" action="delete" strict="true">
    <data xmlns="imaginary"/>
  </query>
</iq>

RECIPIENT:
<iq
    type="error"
    from="hamlet@shakespeare.lit/denmark"
    to="hamlet@shakespeare.lit/denmark"
    id="1002">
    <error code="404">Not Found</error>
    <data xmlns="imaginary"/>
  </query>
</iq>

With strict actions disabled, the absence of existing data will not cause the delete action to fail. Here we show iq:private, and strict actions with no existing data on the server.

SENDER:
<iq type="set" id="1003">
  <query xmlns="jabber:iq:private" action="delete" strict="false">
    <data xmlns="imaginary"/>
  </query>
</iq>

RECIPIENT:
<iq
    type="result"
    from="hamlet@shakespeare.lit/denmark"
    to="hamlet@shakespeare.lit/denmark"
    id="1003"/>

7.1 Description¶

In order to define an action protocol that uses the <query/> behavior defined in this document, you must specify the following:

• The actions (create, read, update, delete) supported in the action protocol.
• The matching semantics for determing if data exists/collides.
• The default "strict" attribute ('true' or 'false'). This may be defined for each action supported or for all actions supported.
• Whether the "strict" attribute may be set by the user. If the attribute may not be set, the strict attribute will always hold the default value.

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