While an OTF is any system or facility in which multiple third-party buying and selling interests interact in the system, a systematic internaliser should not be allowed to bring together third-party buying and selling interests. For instance, a so-called single-dealer platform, where trading always takes place against a single investment firm, should be considered a systematic internaliser, were it to comply with the requirements included in this Regulation. However, a so-called multi-dealer platform, with multiple dealers interacting for the same financial instrument, should not be considered a systematic internaliser.