Content deleted Content added
The paper is misleading. |
|||
Line 10:
:The example given is for ''parsing'' sentences into NP, VP and so on, which is more than [[part-of-speech tagging]]. It may be more common to introduce CYK with artificial examples, but I don't see anything wrong with using an example from an application area. [[Computational linguistics]] is one of the areas where CYK is applied, and CYK is sometimes studied as part of a CL curriculum. But I've reconstructed the grammar from the example and added it to the article. It should now make more sense. -- [[User:UKoch|UKoch]] ([[User talk:UKoch|talk]]) 17:25, 20 December 2011 (UTC)
==I don't like the article either ==
The fact that binary form (no RHS longer than 2) should be used, rather than CNF has been known for about 40 years. It was not published, because it was considered obvious, as the complexity results from the length of right-hand sides. It is also the only way to preserve conveniently the shape of parse trees.
Beau Shiel had a nice paper about it at Coling 76. The empty word is a problem that cannot be escaped, if parse-trees are to be preserved, which is implied by the name parser (but sometimes not described with the algorithm). If no parse tree is kept, it is a recognizer.
For building the parse-tree it is always necessary to store a list of nodes with at least one for each non-terminal found.
The proper way to write for an encyclopedia is to give the modern and simpler description first. Then to give some historical details such as the use of CNF in the first versions.
In 1974, Valiant used the Strassen algorithm (1969) to reduce the complexity, but the complexity of matrix multiplication was reduced since then, first by Coppersmith–Winograd (1990), then by Williams (2011). It should be better to discuss usability on the basis of Strassen's algorithm, which is the only one that has a chance of being meaningful.
==Explain practical parse tree generation!==
| |||