Cela fonctionne parfaitement en fait il me manquait le XML Adaptor. 

Merci beaucoup

Merci @Lorenzo Scalese ,

En revanche je me retrouve avec un "Method does not exist" lié au reader.Next 

J'ai pourtant mes 2 classes : 

Class replic.msg.XML Extends (%Persistent, %XML.Adaptor, Ens.Request)
{
Property Table As%String(MAXLEN = "");Property Action As%String(MAXLEN = "");Property CleIris As%String;Property nIdentifiant As%String;Property IdIris As%String;Property Contenu As%String;
}

Class replic.msg.XMLStructure Extends%Persistent
{
Parameter XMLNAME = "data";Property tablename As list Of replic.msg.XML(XMLPROJECTION = "ELEMENT");
}

Method readXML(pRequest As Ens.StreamContainer, pResponse As replic.msg.XMLStructure) As%Status
{
    set tsc             = $$$OKset reader          = ##class(%XML.Reader).%New()

    //set pResponse       = ##class(replic.msg.XMLStructure).%New()#dim data  As replic.msg.XMLStructure
	#dim tableName As replic.msg.XML
    do pRequest.Stream.Rewind()

    do reader.Correlate("data","replic.msg.XMLStructure")
    set status              = reader.OpenStream(pRequest.Stream)
    
    Do reader.Next(.data)

    Set key = ""Set tableName = data.tablename.GetNext(.key)
	While key '= "" {
		set^debug() = tableName.Table
		Set tableName = data.tablename.GetNext(.key)
	}
	}

Mon erreur : 

ERREUR <Ens>ErrException: <METHOD DOES NOT EXIST>Next+25^%XML.Reader.1 *XMLNew,replic.msg.XMLStructure -- - connecté en tant que '-' numéro - @''