4.5.1.1 Unilateral design and IP licensing The first cluster of approaches includes those that are marked by a comparatively low degree of collaboration between the systems that are interconnecting. Unilateral design occurs when a market participant designs its products or services in a way that allows other players to ofer interoperable products or services. The range of possibilities in this cluster of more \"unilateral\" approaches is considerably broad. For example, companies often use APIs as a unilateral invitation for others to interconnect. In the case of single-sign-on, digital ID oferings, companies like Facebook ofer an open API that any app or online store can utilize, provided they comply with Facebook’s rules for accessing the API. Twiter’s revocation of its open API is a cautionary tale of how reliance upon unilateral forms of interop may be risky, because they can be withdrawn as easily as they are ofered. Another important and related way to achieve interop with minimal collaboration is through IP licensing, in which one party grants another access to technology, specifications, and/or rights associated with the technology’s use. The efectiveness of a licensing approach to interoperability not only depends on the company's willingness to grant a licence in the first place, but also on the terms in the licensing agreement.The scope of -- and compensation for -- the licence plays a particularly important role. IP licensing can be a cost-eficient path toward a higher degree of interoperability, especially in cases where transaction costs are minimized through sophisticated and \"streamlined\" licensing procedures. The flexibility of a licensing arrangement may decrease, however, if the ecosystem changes. This was precisely the patern observed in the publishing dispute between Hachete and Amazon. When the market was relatively immature, the licensing agreements between the publishers and e-book makers were fairly simple, largely following existing licensing models. However, as the market matured and Amazon’s Kindle became the dominant technical platform, the book publishers feared a loss of flexibility in the licensing terms. At that point, the licensing process became far more fraught, Trends in Telecommunication Reform 2016 111 Chapter 4 Figure 4.5: Approaches to interop NON-REGULATORY APPROACHES (PRIVATE ACTORS)REGULATORY APPROACHES (STATES ACTORS)COLLABORATIVE APPROACHES UNILATEAL APPROACHES unilateral design mandating standards reverse engineering disclosure of information IP licensing transparency for consumers technical collaboration public procurement Source: John Palfrey & Urs Gasser, Interop (2012)