"The 'jabber:iq:version' namespace provides a standard way for Jabber entities to exchange information about the software version used by the entities. The information is communicated in a request/response pair using an <iq/> element that contains a <query/> scoped by the 'jabber:iq:version' namespace. The following children of the <query/> are allowed in an IQ result:
<name/> – The natural-language name of the software. This element is REQUIRED in a result.
<version/> – The specific version of the software. This element is REQUIRED in a result.
<os/> – The operating system of the queried entity. This element is OPTIONAL in a result (see also the Security Considerations)."