Hello, my friends. This is my second post about this course. From the forth lecture, I've learned so much and I can't wait to share it with you.
From some examples of product, book and micro-blogging, I've developed a clearer understanding about the basic terms such as entity, attributes, opinion holder(the person who express opinions on an entity form a review, a rating, a twitter message, etc). And the concept of sentiment analysis, which is the field of study involving information retrieval and computational linguistics that analyzes people’s opinions, sentiments, evaluations, appraisals, attitudes, and emotions towards entities such as products, services, organizations, individuals, issues, events, topics, and their attributes.
These useful information can be used in many applications. For instance, how people perceive an entity, event monitoring, collect customers’ opinions and information to make decisions on what to buy, understand what do people of different places think about the same thing, learning analytics etc. Then we feel some different descriptions of opinions. Despite some opinions are implicit, we can also know the meaning of them.
The thing attracted me most is a online demo Rosanna showed us on the class. It is a tool can develop and analyze twitter message based on natural language processing. You can switch along the time line. For example, if I select the day, 18th, Jan, 2012. Base on that, the twitter message generate up to that point of time, so how do the people feel about different actors, actress and movies, you can see that there is a trend of development about the opinion, the very strong opinion can be developed among the users, because the twitter users will exchange more message more frequently and their opinion also converge.
Along the development of the time, the opinion of the majority of population, the time of the Oscar should be around. Analyzing the day 26th,2012, people may have very strong opinion, we can see the sudden burst of the opinion. It is based on NLP technic, you just count your computer program, just count about the opinion, word are associated to the actors, actress and movies.
So how can this kind of opinion minings possible. Technics like NLP and classification, test, analysis and polarity etc. I learn some different levels of sentiment classification. They are document level, sentence Level and attribute level. In addition, two methods for sentiment classification are introduced and some limitations are also pointed out. The first one is dictionary-based approach, which focus on checking whether +ve or –ve words appear in the document/sentences to be classified (+ve stands for good, excellent, durable etc. -ve stands for poor expensive etc.). The second one is called supervised learning. We use the documents’ sentiment class to train a classifier.
Another important thing we should do is identifying the aspects of the entity commented on by the people who write the comments. For the sentence below, we can find the aspects or nouns are food, drinks, waiters, the interior of the restaurant. ‘The food in this restaurant is very delicious. There is a large variety of food and drinks. The waiters are very polite and helpful. The interior of the restaurant is also nicely decorated…’ So we should do the aspect-level analysis to extract nouns that appear frequently. In Python NLTK, we can do something like this:
We can then extract the nouns(NN) and choose the most frequently seen ones to be the aspects.
After extracting the nouns, we also need to associate the opinion words with the aspects. There are two methods to find them. First one is finding out the noun that is closest to the opinion word. And second one is developing rules to extract pairs of opinion words and aspects. For example, find the common patterns of words in the different comments.
At the end of the class, Prof. Rosanna showed us some excellent previous students’ group projects, which really gave me lots of ideas about our own project in this term. And I will try my best to complete it and share more wonderful ideas with all of you!




