An Introduction to the CellTree Paradigm (Invited Paper)

This note is a brief introduction to CellTree, a new architecture for distributed data repositories, drawing liberally from our article which introduces the concept in greater detail [15]. A CellTree allows data to be stored in largely independent, and highly programmable cells, which are “assimilated” into a tree structure. The data in the cells are allowed to change over time, subject to each cell’s own policies; a cell’s policies also govern how the policies themselves can evolve. A design goal of the architecture is to let a CellTree evolve organically over time, and adapt itself to multiple applications. Different parts of the tree may be maintained by different sets of parties and the core mechanisms used for maintaining the tree can also vary across the tree and over time. We outline the architecture of a CellTree, along with provable guarantees of liveness, correctness and consistency that can be achieved in a typical instantiation of the architecture. These properties can be guaranteed for individual cells that satisfy requisite trust assumptions, even if these assumptions don’t hold for other cells in the tree. We also discuss several features of a CellTree that can be exploited by applications. Finally, we briefly outline a sample application that can be built upon the CellTree, leveraging its many features.