algorithm to find out if two sentence parts can be joined together

I'm looking to build a开发者_JS百科n algorithm that can join together sentence parts. So, for example, it would know that

"drank it down and ordered a second glass,"

would be able to follow:

"He listened to what she had to say and ordered a glass of wine,"

but

"by trying to know what he could not understand,"

would not.

I'm familiar with the NLTK - any suggestions?

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This is actually proven to be unsolvable. The code would have to have understanding of the meaning of the words to be sure. What you are effectively asking for is a Context-free Grammar (http://en.wikipedia.org/wiki/Context-free_grammar) which simply doesn't exist for human languages.