Carrillo and Lipman boundary:
 Projection of the MSA into series of pairwise alignments
 Assumption: It is not necessary to compute all the combinations
 Every pairwise alignment defines a set of spatial positions
within which the optimal MSA is suposed to be (heuristic)
MSA procedure:
 Calculate all pairwise alignments and associated distances
 Use the distances to build a trial phylogenetic tree
 Calculate pair weights based on the tree (divergence among sequences)
 Produce a heuristic MSA based on the tree
 From alignments and the heuristic MSA, determine the relevant positions
 Perform the optimal alignment (SPscore) within the relevant space

