Question: I've got a requirement of determining whether the entered sentence is positive or negative.... First I thought it is something to do with Social Network analysis and later I realised that it is Sentiment analysis. My first question is what is the difference between these two? I think SNA itself uses SA... plz correct me if i am wrong...

Regarding this I got a very good discussion by Alexander @ [NLP: Qualitatively "positive" vs "negative" sentence](https://stackoverflow.com/questions/122595/nlp-qualitatively-positive-vs-negative-sentence)...

I want to get into this field with the power of open source and preferably with Java (but I am open to others too). Can anyone pls guide me on how to get started and move ahead

Thanks in advance 
Siva

Answer: 
This is sentiment analysis. 

Social Network Analysis doesn't really have anything to do with Sentiment Analysis - social network analysis deals with relationships between people or things - common problems deal with figuring out "clustering" or cliques within a social network, discovering group cohesion, prestige within groups, discovering "ringleaders", etc. 

Sentiment analysis is much closer to natural language processing - taking some textual, audio or video content and attempting to classify it in some way - subjective/objective, agreement/disagreement, etc.

As for tools/APIs that support this - I googled and found this blog post [listing several sentiment analysis and natural language processing tools](http://lordpimpington.com/codespeaks/drupal-5.1/?q=node/5).
RapidMiner is a powerful text mining and sentiment analysis tools. Rapid-I offers RapidMiner training courses on text mining and sentiment analysis:
[Sentiment Analysis, Opinion Mining, and Automated Market Research](http://rapid-i.com/content/view/125/150/).

Best regards,

Frank