I am trying to build a feedback sentiment analyser based on a semantic approach. As an example: "I had safe journey" – assume this is feedback for a driver, provided by a passenger. I need to extract the following information from this sentence:

```
"I had safe journey" -> 
 SUBJECT= "driving"
 SENTIMENT= "positive"

```

I am using NLTK and I referred NLTK Book. I already followed the "Extracting Information from Text" section. That section talks about Chunking using a regular-expression based grammar. But I am confused, there are a number of different sentence patterns for the English language and I don't know how to cover all the possibilities.

Actually, I am new to NLP. I also found "Analyzing Sentence Structure" and "Analyzing the Meaning of Sentences" in the NLTK book. Is chunking enough to achieve my goal and what am I supposed to do?