COAST: Architectures for Decentralized On-Demand Tailored Services

Decentralized systems are systems-of-systems whose services are governed by two or more separate organizations under distinct spheres of authority. Coordinated evolution among the various elements of a decentralized system may be difficult, if not impossible, as individual organizations evolve their service offerings in response to organizationand service-specific pressures, including market demand, technology, competitive and cooperative interests, and funding. Consequently, decentralized services offer unique challenges for evolution and adaptation that reach well beyond any one single organizational boundary. However, clientdriven service customization and tailoring is a powerful tool for meeting conflicting, independent client demands in an environment where disorderly and uneven service evolution predominates. To this end we contribute an architectural style, COmputAtional State Transfer (COAST), designed to provide extensive, but safe and secure, client-directed customization of decentralized services. COAST combines mechanisms from software architecture, cryptography, security, programming languages, and systems, granting application architects flexible provisioning of their core services and assets while, at the same time, protecting those services and assets from attack and misuse.