In this article we present the technological foundations on which an ecosystem of semantic data objects can be implemented on the latest Blockchain based systems. As the most important citizens among the semantic data objects are ontologies, the ecosystem is referred to as Ontospace. The foundations can be characterized by their architectural, cryptographic and transactional aspects. The architectural aspect borrows from the latest Layer-2 protocols of the 3rd generation blockchains and from the rules of Linked Data systems creation. The cryptographic aspect represents an original work that attempts to resolve the issue of efficient hashing of the graph data structures. The transactional aspect is concerned with the graph replication consistency, conditions for the direct access to graph data from the blockchain smart-contracts and with linkage between sidechains bearing semantic objects and the main network. The large parts of the work were implemented in the context of the Ontochain project – a part of the Next Generation Internet EU Initiative.
