Hi All :
As Hadi asked this morning, I just check the definition about "POS guessing".
As [1] described: Naturally, when tagging (POS tagging) real-word texts, one can expect to encounter words which were not seen at the training phase (OOV) and hence not included into the lexicon. This is where word-Pos guessers (POS guessing) take their place.
As [2] introduced: The task of POS guessing is quite different from traditional POS tagging. Traditional POS tagging involves assigning a single POS tag to a word token, provided that it is known what POS tag this word can take on in principle. This task requires a lexicon that lists possible POS tags for all words. However, unknown words are not in the lexicon, so the task of POS guessing of unknown words involves the guessing of a correct POS for an unknown word from the whole POS set of the current language. Obviously, traditional methods of POS tagging cannot effectively solve the problem of POS guessing of unknown words.
As [3] presented: The quality of OOV term detection and POS guessing directly influences the precision of querying more relevant information, and has become a crucial and challenging issue in IR.
[1] Learning Part-of-Speech Guessing Rules from Lexicon: Extension to Non-Concatenative Operations (Coling 1996)
[2] A Method for Automatic POS Guessing of Chinese Unknown Words (Coling 2008)
[3] Fusion of Multiple Features and Supervised Learning for Chinese OOV Term Detection and POS Guessing (IJCAI 2011)
The above three papers introduced the definition of POS guessing, the main differences between POS tagging and POS guessing and the application/importance of OOV detection and POS guessing respectively.
For my understanding, POS guessing and OOV detection are two highly related tasks. I think the POS guessing is the specific task of POS tagging which is only towards to the OOV terms in text.
In addition, the approaches to POS guessing is developing from rule based, statistical based to hybrid based. They mainly depend on the word leading and trailing characters and other morphological features. One can get the details from the above 3 papers.