Hi,

Thanks again for all the informative responses to my question. I also have some words to say.

First, I hope there will be some comparisons between English and Chinese or other languages PoS, which maybe helpful to have a deeper understanding of PoS.

Second, I think there maybe some differences between examples (1) "the church tower" and (2) "the chief executive officer". In (1) the pos of "church" cannot be determined with the context clues alone. But in the dictionary "church" only has one pos so we can determine its pos with a dictionary. But "chief" has two pos in the dictionary, and both of them (noun and adjective) can be placed before a noun. So we can not determine its pos with context and dictionary alone. Maybe we should have a rule for such words: if one word is both noun and adjective and it appears before a noun, then it should be tagged as adjective instead of noun. With such a rule we can make a clear and consistent decision. In this sense the two examples are different. But in (2) no matter what class “chief” is tagged, it will be the modifier of “executive officer”. If the purpose of pos tagging is to parse the sentence it seems that it doesn't matter what class we tag it. In this sense it maybe true that pos is contextual.

But in Chinese it is different. In the example:

一件 包装/v n 精美 的 礼品
(1. a present whose decoration is wonderful 2.a present which is decorated to be wonderful)

If we tag 包装 as noun, the relation between 包装 and 精美 will be Subject and Predicate (the decoration is wonderful). If we tag 包装 as verb, the relation between 包装 and 精美 will be Predicate and Complement (be decorated to be wonderful). Moreover, no matter what tag we put on 包装 and what relations between 包装 and 精美, the meaning of this phrase is the same. The Chinese speakers never care about those differences. So I call this as vagueness but not ambiguity because we cannot and need not resolve it.

I don't know whether there is such thing in English. It is also welcome to help me to analyze this Chinese phrase.