Blockchain technology enables an ecosystem for decentralized applications with interesting properties: transparency, auditability or censorship resistance. However, the field faces many challenges. For example, there is a lack of interoperability at several levels: between projects on a same blockchain, between different blockchains, or between blockchains and existing systems. This is due to the fact each blockchain uses its own standard and economic model. Moreover, there are also scalability issues. Firstly, the number of transactions the network can handle is limited, which prohibits the use of the technology for applications needing a lot of interactions. Secondly, transactions grouping into blocks induce a latency that disallows the use of blockchains for real-time applications. Finally, transactions complexity depends on the blockchain design choices, regarding the consensus algorithm and the machine operations allowed. For example, data storage is very expensive.

With this PhD work, we hope to propose a framework that can improve interoperability for decentralized blockchain applications. It involves developing models, methods and formal tools for designing decentralized applications. In particular, the following aspects have to be considered:

1. Semantic representation of objects used in decentralized applications: transactions on a blockchain, images, videos, or physical objects,
2. Storage of these objects,
3. Exchange protocols of these objects between users,
4. Validation of their integrity
5. Their integration in the application, ensuring interoperability and scalability of the application.

This framework will be validated in the context of blockchain video game development. It is a complex use case, as video games assets are diverse and storage intensive. Video games assets can be sounds, images, videos, or models of 3D objects used in the game. Furthermore, the latency issue is crucial for a real-time game.