We define a method how digital ecosystems (including data spaces) may autonomously define and "advertise" credentials they issue or they trust in the form of so-called ecosystem trust profiles. An ecosystem trust profile collects all (verifiable) credentials and issuers sorted by trust scope accepted ("trusted") by a particular ecosystem. We then show how a minimal trust relation between ecosystems may be defined using ecosystem trust frameworks of different ecosystems and explore a few of its properties. A first application of the theory is given for a use case in the manufacturing realm where different international ecosystems need to agree on certain credentials for various scopes of trust such as identity, service compliance, and other conformance standards. We implement this requirement by identifying and discussing two different definitions of credential equivalence for a given trust scope, one requiring additional cross-ecosystem governance or coordination, one not. The second approach demonstrates how to solve the so-called cross-ecosystem trust dilemma, that is, the problem how ecosystems can establish cross-ecosystem trust while, at the same time, allowing them to fully retain their sovereignty. A fragility theorem demonstrates that this sovereignty leads trust to be unstable without any additional coordination or governance mechanisms on top of (and outside to) ecosystem trust profiles. We extend our method to data spaces in particular and propose a novel rigorous definition of cross-data space interoperability. This allows us to prove the proposition that the extent of interoperability between two data spaces is exactly determined by the amount of commonality in their respective ecosystem trust profiles.

翻译：我们定义了一种方法，使数字生态系统（包括数据空间）能够自主定义并以所谓生态系统信任概要的形式“宣传”其所签发或信任的凭证。生态系统信任概要收集了特定生态系统所接受的（即“信任的”）按信任范围分类的所有（可验证）凭证及签发者。随后，我们展示了如何利用不同生态系统的生态系统信任框架来定义生态系统间的最小信任关系，并探讨了其若干性质。该理论的首个应用场景来自制造业领域，其中多个国际生态系统需要针对身份、服务合规性及其他符合性标准等不同的信任范围就特定凭证达成共识。我们通过识别并讨论给定信任范围内凭证等价的两种不同定义来实现这一需求：一种需要额外的跨生态系统治理或协调，另一种则不需要。第二种方法展示了如何解决所谓的跨生态系统信任困境，即生态系统如何在完全保持自身主权的同时建立跨生态系统信任。一个脆弱性定理表明，若在生态系统信任概要之上（及其外部）没有额外的协调或治理机制，这种主权将导致信任不稳定。我们将方法特别扩展至数据空间，并提出了一种关于跨数据空间互操作性的全新严格定义。由此得以证明：两个数据空间之间的互操作性程度完全由它们各自生态系统信任概要中的共同部分决定。