High throughput, tree automata based XML processing using FPGAs

A novel and efficient approach to XML processing using FPGAs, based upon the sound theoretical formalism of tree automata, is presented. The approach enables the key tasks of schema validation and query to be performed in a unified manner. A remarkably simple implementation of a tree automaton in hardware, as a pair of interacting automata with the states of one forming the input to the other, is described. The implementation can process one XML token in at most two clock cycles. Also, the throughput is achieved for any schema grammar or query (that can be accommodated in the state tables) independent of its complexity. Further, use of tree automata offers greater expressive power for specifying schemas as well as queries than in previous hardware based approaches. Detailed performance evaluation demonstrates the significant throughput improvements of the proposed tree automata based approach compared with software as well as earlier FPGA based approaches. The implementation of XML schema validation on a mid-range FPGA provides sustained throughput from 1.7 to 3.1 Gbps, yielding a five to ten times speedup over an efficient software approach. Due to the very compact implementation, multiple instances can be utilized to further make significant improvements in throughput.