def construct_bericht_sent_query(graph_uri, bericht_uri, verzonden):
    """
    Construct a SPARQL query for marking a bericht as received by the other party (and thus 'sent' by us)

    :param graph_uri: string
    :param bericht_uri: URI of the bericht we would like to mark as sent.
    :param verzonden: ISO-string representation of the datetetime when the message was sent
    :returns: string containing SPARQL query
    """
    q = """
        PREFIX schema: <http://schema.org/>

        INSERT {{
            GRAPH <{0}> {{
                <{1}> schema:dateReceived "{2}"^^xsd:dateTime.
            }}
        }}
        WHERE {{
            GRAPH <{0}> {{
                <{1}> a schema:Message.
            }}
        }}
        """.format(graph_uri, bericht_uri, verzonden)
    return q