Tanner graph
A Tanner graph is a bipartite Graph used to specify constraints or equations which specify Error correcting codes.
Origins
Tanner graphs were proposed by Michael Tanner as a means to create larger error correcting codes from smaller ones using recursive techniques. Tanner discussed lower bounds on the codes obtained from these graphs irrespective of the specific characteristics of the codes which were being used to construct larger codes.
Computational complexity of Tanner graph based methods
The advantage of these recursive techniques is that they are computationally tractable.