Distributed ledgers technologies can be categorized in terms of their data structures, consensus algorithms, permissions, and mining characteristics.[14] DLT data structure types range from simple linear data structures (blockchains) to more complex Directed Acyclic Graphs (DAGs) and hybrid data structures. DLT consensus algorithm types vary from conventional Proof-of-Work (PoW) and Proof-of-Stake (PoS) algorithms to more sophisticated DAG consensus building and voting algorithms. DLT permission types are generally either permissioned (public) or permissionless (private).[15] DLT mineability types are generally either 'Mined' or 'Non-Mined', where the latter typically indicates 'Pre-Mined' cryptocurrencies, such as XRP or IOTA.[16]