Automatic Hierarchy Discovery and Opinion Mining of Political Blogs

1. Automatic Hierarchy Discovery and Opinion Mining of Political Blogs Amit Goyal Kristi McBurnie November 28, 2007

2. Outline • Introduction • Previous Work • Our Approach • Example • Challenges and Future Work • Milestones • Conclusion

3. Introduction • The Web contains a wealth of opinions about products, politics, newsgroup posts, review sites, and elsewhere • Our interest: to mine opinions expressed in user generated content

4. Applications • Businesses and Organizations • Market Intelligence: A huge amount of money is spent to find consumer sentiments and opinions • Opinion Polls, surveys • Individuals interested in other opinions when • Purchasing a product • Finding opinion on political topics • Using a service etc. • Smart Ads • Place an ad when one praises a product • Place an ad from a competitor if one criticizes a product • Opinion Search • Provide search for opinions • Give me opinions on “gmail” • Give me comparisons between “gmail vs yahoomail”

5. Types of opinions • Direct Opinions: sentiment expressions on objects. E.g. policies, politicians, movies, products • E.g. “I find myself in support of the Senate Judiciary Committee, which approved legislation that clears the way for millions of undocumented workers to continue working in America and seek citizenship.” • Comparisons: relations expressing similarities or differences of more than one object. • E.g. “I think Bush will beat Kerry in the presidential elections” or “The lens quality of Camera A is better than Camera B”

6. Problem Statement • Given a object and a collection of reviews on it, the task is • Identification of features • Making hierarchy of features • Sentiment Analysis: Determining the orientation and strength • Provide a visualization (summary)

7. Previous Work • Mainly focused on product and movie reviews • Feature Extraction • Opinion Observer (Hu and Liu, 2004) • Opine (Popescu and Etzioni, 2005) • Red Opal (Scaffidi, 2007) • Hierarchical Discovery • To be filled by kristi

8. Previous Work Opinion Observer • By Bing Liu and Minqing Hu • Feature Extraction • Identify Nouns using POS tagging • Identify Noun phrases by Association Rule Mining • Compactness pruning, redundancy pruning • Opinion word extraction • Infrequent feature identification • 72% precision and 80% recall

9. Previous Work OPINE • Feature Extraction • First, extract nouns and noun phrases, retains those with frequency greater than some threshold • Evaluates each noun phrase by computing the PMI (point-wise mutual information) scores between the phrase and meronymy discriminators associated with the product class • E.g. “of scanner”, “scanner has”, “scanner come with” etc. for the Scanner class • PMI(f,d) = Hits(d+f) / {Hits(d) * Hits(f)} • Then, PMI score are converted to binary features for a Naïve Bayes Classifier, which outputs a probability associated with each fact • Compared to Hu and Liu work, 22% better precision and 3% lower recall

10. Previous Work Red Opal • 3 components: • Feature Extractor • Product Scorer • User Interface • Performs better than Opinion Observer

11. Previous Work Red Opal • Feature Extraction • POS tagging, takes noun and noun phrases as potential features • Use lemma frequency to rank the features • Product Scoring: Score of feature f of product p • o(r,f) is the number of occurrences of feature f in review r • w(r,f) is the weight of feature f in review r

12. Previous Work Clustering • Conceptual clustering • CLUSTER/2 • Places object descriptions and attributes together to obtain domain-dependent goals • COBWEB • Favours classes that maximize the information that can be predicted from knowledge of class membership • Hierarchical clustering • BIRCH • Hierarchically cluster elements in a dataset • Level of clustering quality = level in the hierarchy

13. Previous Work Hierarchy Discovery • Han and Fu define formally as “A sequence of mapping from a set of lower-level concepts to their higher-level correspondences” • DBLearn automatically discovered a hierarchy of concepts for the purpose of data mining • Ie: birthplace may have the following hierarchy: city, province, country • Foreman et al. • Trains categorizers and automatically constructs hierarchy of categories using human trainers • Good GUI • Difficult for novice users and hard to optimize

14. Previous Work

15. Previous Work Hierarchy Discovery • Sanderson and Croft • Automatically develop hierarchy in web documents • Organize extracted words/phrases using subsumption • No clustering or training techniques • Yang and Lee • Hierarchies of web directories • Text mining to discover relationships between documents and between words • Cluster them into document and word maps

16. Previous Work Sentiment Analysis • Esuli and Sebastiani • 3 stages: • Determine subjective/objective polarity • Determine positive/negative polarity • Determine strength of the positive/negative polarity • Uses SentiWordNet to assign 3 scores to each word (objectivity, positivity, negativity)

17. Previous Work Sentiment Analysis • Pang and Lee • Only subjective sections of the movie review • Machine learning techniques • Pair-wise relations between extracts to build an undirected graph • Minimum cut • Efficient and results in higher accuracy rates • Agarwal and Bhattacharyya: • SVM classifier • Determine strength of polarity of subjective adjectives in good vs bad classification based on WordNet’s synonymy graph • Applied cut-based graph similar to Pang et al • Reached accuracies of 84%-95.6%

18. Our proposal Apply feature extraction and opinion mining in political domain Applications in political domain: Automatic opinion polls Identification of local/global issues in elections Target campaigning in elections Impact of speech Output: <politician, topic, opinion, polarity> Objects are politicians Categories are political organizations Topic may be policies, issues etc In this project, we focus mainly on feature extraction and their hierarchy discovery

19. Our Approach Observations Two kinds of opinions: Direct – talks about single object Comparison – talks about multiple objects Two kinds of information Facts (objective) Opinions (subjective) Sentiment Analysis can be done only on subjective information Although, features occur both categories, subjective sentences are noisy

20. Comparison to product domain

21. Our Approach

22. Our Approach • Perform feature extraction • Split into objective and subjective phrases • Hierarchy discovery on features from objective sentences • Sentiment analysis on features from subjective sentences

23. Our Approach Feature Extraction • Extract the features • Extract nouns from POS tagging • Extract noun phrases from Association Rule Mining • Pruning • Rank the features based on lemma frequency • Identify the subjectivity of all sentences • Mine the opinion words (adjectives) • Use key phrases dictionary (e.g. “can you believe”, “I think”, “I recommend” etc) • Visual differences – factual data is often represented in quotes

24. Our Approach Hierarchy Discovery • 3 approaches: • Subsumption • Sanderson and Croft • Look at every pair of terms and apply subsumption • X subsumes Y if the documents in which Y occurs are a subset of the documents in which X occurs • P(X|Y) = 1 and P(Y|X) < 1 • Clustering • Use DBpedia and/or YAGO X Y

25. Our Approach Hierarchy Discovery • 3 approaches: • Subsumption • Clustering • Yang and Lee • Cluster phrases by co-occurrance • Using unsiupervised learning algorithm  SOM networks • Organizes phrases into a 2D map of neurons • According to similarity of vectors • 3 Steps: • Training process • Assigning phrases to a neuron • Labelling process • Use DBpedia and/or YAGO

26. Our Approach Hierarchy Discovery • 3 approaches: • Subsumption • Clustering • Find a group of dominating clusters (neurons) • Make these as superclusters and put neighbours one level down • Repeat for lower level of hierarchy under each subcluster • Use DBpedia and/or YAGO

27. Our Approach Hierarchy Discovery • 3 approaches: • Subsumption • Clustering • Use DBpedia and/or YAGO • DBpedia provides 3 classification schemes: • Wikipedia categories • YAGO classification • Word Net Sysnet Links

28. Our Approach Hierarchy Discovery • 3 approaches: • Subsumption • Clustering • Use DBpedia and/or YAGO

29. Our Approach Hierarchy Discovery { Dbpedia and YAGO { Clustering and Subsumption

30. Our Approach Sentiment Analysis • 2 ways to approach this: • Subjective phrases • What does the public think about each policy • Objective phrases • What is the policy • Rank parties from each policy on a scale from right-wing to left-wing

31. Our Approach Sentiment Analysis • Subjective phrases • What does the public think the policy • Pang and Lee • Cut-based classification (Pang and Lee) • Individual scores • Association scores • Partition Cost • A cut (S,T) of G is a partition of its nodes into sets S = {s} U S’ and T = {t} U T’, where s not contained in S’ and t is not contained in T’. Its cost cost(S,T) is the sum of the weights of all edges crossing from S to T • A minimum cut of G is one of minimum cost.

32. Our Approach Sentiment Analysis • Subjective phrases • What does the public think about each policy • Agarwal and Bhattacharyya • Determine adjective strength • Cut-based classification between sentences (Pang and Lee) • Cut-based classification between documents • Improved accuracy

33. Our Approach Sentiment Analysis • Objective phrases • What is the policy • Rank parties from each policy on a scale from right-wing to left-wing • Definition of polarity would be left/right using a comparison of left-wing and right-wing policies/ideals • Instead of traditional positive/negative using the ideal words ‘poor’ and ‘excellent’ Right-wing (Conservative) Left-wing (Liberal)

34. Example Ideal case: • The economic cost of the war in Iraq is estimated to total $1.3 trillion – roughly double the amount the White House has requested thus far, according to a new report by Democrats on Congress’ Joint Economic Committee. I think this is an absurd amount of money to be spending on killing people and freeing oil fields. • Political Organization = Republicans • Politician = George Bush • Topic = War in Iraq • Sub-topic = cost • Opinion words = absurd, killing, freeing • Polarity = negative

35. Example Feature Extraction: • The economic cost of the war in Iraq is estimated to total $1.3 trillion – roughly double the amount the White House has requested thus far, according to a new report by Democrats on Congress’ Joint Economic Committee. I think this is an absurd amount of money to be spending on killing people and freeing oil fields. • Noun phrases: economic cost, war in Iraq, amount, report, amount, money, people, oil fields • Proper nouns: White House, Democrats on Congress Joint Economic Committee • Frequent features: economic cost, war in Iraq, money, oil fields, White House

36. Example Identification of Subjectivity • The economic cost of the war in Iraq is estimated to total $1.3 trillion – roughly double the amount the White House has requested thus far, according to a new report by Democrats on Congress’ Joint Economic Committee. I think this is an absurd amount of money to be spending on killing people and freeing oil fields. • Opinion words: think, absurd • 1st sentence is objective, and 2nd is subjective • Interesting features: economic cost, war in Iraq

37. Example Hierarchy Discovery – step 1 • The economic cost of the war in Iraq is estimated to total $1.3 trillion – roughly double the amount the White House has requested thus far, according to a new report by Democrats on Congress’ Joint Economic Committee. I think this is an absurd amount of money to be spending on killing people and freeing oil fields. • Identification of category/object for proper nouns using DBpedia • Category = Republicans • Object = George Bush

38. Example

39. Example Hierarchy Discovery – step 2 • The economic cost of the war in Iraq is estimated to total $1.3 trillion – roughly double the amount the White House has requested thus far, according to a new report by Democrats on Congress’ Joint Economic Committee. I think this is an absurd amount of money to be spending on killing people and freeing oil fields. • Identification of policy hierarchy using subsumption and clustering • Policies are derived from interesting features • economic cost, war in Iraq

40. Example

41. Example Sentiment Analysis • The economic cost of the war in Iraq is estimated to total $1.3 trillion – roughly double the amount the White House has requested thus far, according to a new report by Democrats on Congress’ Joint Economic Committee. I think this is an absurd amount of money to be spending on killing people and freeing oil fields. • Opinion is the subjective sentence • Polar words: absurd, spending, killing, freeing • Polarity: Negative

42. Challenges • Difficult to distinguish between objective and subjective information • Opinion words also occur in objective sentences • Identification of spam blogs • Identification of implicit features • Mapping politician to the policy in comparison blogs • Deciding on a distance measurement for clustering

43. Future Work • Implementation of algorithms • Summarization of opinions • Visualization • Refinements

44. Milestones  • Decide on domain • Read previous works • Decide on an approach that is best for the domain • Write up an example to illustrate it • Challenges and future work • Presentation • Write the paper       

45. Questions?

46. Previous Work OPINE (Backup Slide) • Overall Process

47. Previous Work Opinion Observer (Backup Slide) • By Bing Liu and Minqing Hu

48. Types of opinions • Direct Opinions: sentiment expressions on objects. E.g. policies, politicians, movies, products • E.g. “I find myself in support of the Senate Judiciary Committee, which approved legislation that clears the way for millions of undocumented workers to continue working in America and seek citizenship.” • Comparisons: relations expressing similarities or differences of more than one object. • E.g. “I think Bush will beat Kerry in the presidential elections” or “The lens quality of Camera A is better than Camera B”