When logging in to an EPP session, it is necessary to provide a list of the schemas for the objects to be referenced during the session.

The following schemas can be specified for Standard EPP

• urn:ietf:params:xml:ns:contact-1.0
• urn:ietf:params:xml:ns:domain-1.0
• urn:ietf:params:xml:ns:host-1.0

The host schema is imported by the domain schema, so it's not compulsory to specify it.  Otherwise, you can only manipulate objects defined by the schemas specified at login.

You cannot specify Nominet EPP schemas at the same time as Standard EPP schemas.  Consequently once you have logged in you can either use Nominet EPP commands or Standard EPP commands, but not both.  It is necessary to log out and then log back in to switch between Nominet EPP and Standard EPP.

Extensions to the Standard EPP schema set can be found here. These schemas account for the major differences between the Standard EPP and the Nominet business models. In order to use an extension, you must also specify (in an <objURI> element) the relevant base schema.