 The method most frequently employed nowadays in fully analyzing sentential structure is chart parsing.  This is a conceptually simple and efficient dynamic programming method closely related to the algorithms just mentioned; i.e., it begins by assigning possible analyses to the smallest constituents and then inferring larger constituents based on these, until an instance of the top-level category (usually S) is found that spans the given text or text segment. There are many variants, depending on whether only complete constituents are posited or incomplete ones as well (to be progressively extended), and whether we proceed left-to-right through the word stream or in some other order (e.g., some seemingly best-first order). A common variant is a left-corner chart parser, in which partial constituents are posited whenever their “left corner”—i.e., leftmost constituent on the right-hand side of a rule—is already in place. Newly completed constituents are placed on an agenda, and items are successively taken off the agenda and used if possible as left corners of new, higher-level constituents, and to extend partially completed constituents. At the same time, completed constituents (or rather, categories) are placed in a chart, which can be thought of as a triangular table of width n and height n (the number of words processed), where the cell at indices (i, j), with j &gt; i, contains the categories of all complete constituents so far verified reaching from position i to position j in the input.  The chart is used both to avoid duplication of constituents already built, and ultimately to reconstruct one or more global structural analyses. (If all possible chart entries are built, the final chart will allow reconstruction of all possible parses.) Chart-parsing methods carry over to PCFGs essentially without change, still running within a cubic time bound in terms of sentence length. An extra task is maintaining probabilities of completed chart entries (and perhaps bounds on probabilities of incomplete entries, for pruning purposes).