LZWL: Difference between revisions

This article has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these messages) This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "LZWL" – news · newspapers · books · scholar · JSTOR (January 2013) (Learn how and when to remove this message) This article's tone or style may not reflect the encyclopedic tone used on Wikipedia. See Wikipedia's guide to writing better articles for suggestions. (August 2009) (Learn how and when to remove this message) This article uses bare URLs, which are uninformative and vulnerable to link rot. Please consider converting them to full citations to ensure the article remains verifiable and maintains a consistent citation style. Several templates and tools are available to assist in formatting, such as reFill (documentation) and Citation bot (documentation). (September 2022) (Learn how and when to remove this message) (Learn how and when to remove this message)

LZWL is a syllable-based variant of the character-based LZW compression algorithm^[1][2] that can work with syllables obtained by all algorithms of decomposition into syllables. The algorithm can be used for words too.

Algorithm LZWL can work with syllables obtained by all algorithms of decomposition into syllables. This algorithm can be used for words too.

In the initialization step the dictionary is filled up with all characters from the alphabet. In each next step it is searched for the maximal string S, which is from the dictionary and matches the prefix of the still non-coded part of the input. The number of phrase S is sent to the output. A new phrase is added to the dictionary. This phrase is created by concatenation of string S and the character that follows S in file. The actual input position is moved forward by the length of S. Decoding has only one situation for solving. We can receive the number of phrase, which is not from the dictionary. In this case we can create that phrase by concatenation of the last added phrase with its first character.

The syllable-based version uses a list of syllables as an alphabet. In the initialization step we add to the dictionary the empty syllable and small syllables from a database of frequent syllables. Finding string S and coding its number is similar to the character-based version, except that string S is a string of syllables. The number of phrase S is encoded to the output. The string S can be the empty syllable.

If S is the empty syllable, then we must get from the file one syllable called K and encode K by methods for coding new syllables. Syllable K is added to the dictionary. The position in the file is moved forward by the length of S. In the case when S is the empty syllable, the input position is moved forward by the length of K.

In adding a phrase to the dictionary there is a difference in the character-based version. The phrase from the next step will be called S1. If S and S1 are both non-empty syllables, then we add a new phrase to the dictionary. The new phrase is created by the concatenation of S1 with the first syllable of S. This solution has two advantages: The first is that strings are not created from syllables that appear only once. The second advantage is that we cannot receive in decoder number of phrase that is not from dictionary.

• Detailed description