In this paper we present X -TNL, an XML-based [4] language for carrying on trust negotiations. The language provides a flexible way of qualifying the parties involved in the negotiation, which relies on a distinction between credentials and declarations. Additionally, it provides an expressive XML encoding of disclosure policies, where a disclosure policy regulates the disclosure of a resource by imposing conditions on both credentials and negotiations. The language we provide has been especially conceived for handling multiple and heterogeneous credentials and it is flexible enough to express a wide range of protection requirements. In the paper, besides describing the language in full details, we show examples of its applicability.