[Standards] XEP-107 and XEP-108: Empty Value?

Stephan Maka stephan at spaceboyz.net
Sun May 4 23:14:40 UTC 2008

Florian Zeitz <florian.zeitz at gmx.de> wrote:
> Stephan Maka wrote:
> > Publish-Subscribe defines an item deletion use-case[1]. However, it
> > is optional for PEP[2]. Should (client) implementations handle this?
> Ah yes, I figured that out in the meantime. Probably should have
> answered to myself earlier.

No, I think the missing part is that only some PEP extensions include
an empty variant of their XML representation to reset the indicated
event node. There is a fine »Delete And Notify« request in section of XEP-0060 (Publish-Subscribe), but no PEP XEP is using it,
although it is the generic PubSub way of retracting an item.

> But I don't know why you think it is optional. XEP-0163 says a PEP
> service MUST implement it. I think client implementations should

From http://www.xmpp.org/extensions/xep-0163.html#defaults
| 5. Recommended Defaults
| A PEP service MUST:
|     * Support the node discovery, node creation, node deletion,
|       publish item, subscribe, unsubscribe, and item retrieval use
|       cases specified in XEP-0060.

node deletion:

|     * Support the "auto-create", "auto-subscribe", and
|       "filtered-notifications" features.
|     * Support the "owner" and "subscriber" affiliations.
|     * Support the "presence" access model and set it to the default.
|     * Support the "open", "roster", and "whitelist" access models.
|     * Treat the account owner's bare JID (<localpart at domain.tld> or
|       <domain.tld>) as a collection node (i.e., as the root collection
|       node for the account's virtual pubsub service).
|     * Default the 'deliver_notifications' configuration option to true
|       (i.e., deliver payloads by default).
|     * Default the 'send_last_published_item' configuration option to
|       true (i.e., send the last publish item by default).
| A PEP service MAY support other use cases, affiliations, access
| models, and features, but such support is OPTIONAL.

There's a "MAY". Perhaps the PEP-using XEPs like User Tune should
require it for their purpose of indicating stopped activity.

No occurrences of "delete" or "retract" anywhere else in XEP-0163.

> handle this. But most don't. It works in Miranda, but it doesn't in
> Pidgin and Gajim. I'm not sure about Psi as I have not tested it.
> For Gajim I've written a patch which is currently in their Trac.

Yip, and this should be specified. Gajim trunk is sensible to the
currently-specified empty element event.


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