Mining Frequent Patterns Without Candidate Generation


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Mining Frequent Patterns Without Candidate Generation

  1. 1. Data Mining: Concepts and Techniques <ul><li>© Jiawei Han and Micheline Kamber </li></ul><ul><li>Intelligent Database Systems Research Lab </li></ul><ul><li>School of Computing Science </li></ul><ul><li>Simon Fraser University, Canada </li></ul><ul><li> </li></ul>Some of these slides are taken with some modifications from:
  2. 2. Acknowledgements <ul><li>This work on this set of slides started with Han’s tutorial for UCLA Extension course in February 1998 </li></ul><ul><li>Dr. Hongjun Lu from Hong Kong Univ. of Science and Technology taught jointly with me a Data Mining Summer Course in Shanghai, China in July 1998. He has contributed many excellent slides to it </li></ul><ul><li>Some graduate students have contributed many new slides in the following years. Notable contributors include Eugene Belchev, Jian Pei , and Osmar R. Zaiane (now teaching in Univ. of Alberta). </li></ul>
  3. 3. Where to Find More Slides? <ul><li>Tutorial sections (MS PowerPoint files): </li></ul><ul><ul><li> </li></ul></ul><ul><li>Other conference presentation slides (.ppt): </li></ul><ul><ul><li> or </li></ul></ul><ul><li>Research papers, DBMiner system, and other related information: </li></ul><ul><ul><li> or </li></ul></ul>
  4. 4. Introduction <ul><li>Motivation: Why data mining? </li></ul><ul><li>What is data mining? </li></ul><ul><li>Data Mining: On what kind of data? </li></ul><ul><li>Data mining functionality </li></ul><ul><li>Are all the patterns interesting? </li></ul><ul><li>Classification of data mining systems </li></ul><ul><li>Major issues in data mining </li></ul>
  5. 5. Motivation: “Necessity is the Mother of Invention” <ul><li>Data explosion problem </li></ul><ul><ul><li>Automated data collection tools and mature database technology lead to tremendous amounts of data stored in databases, data warehouses and other information repositories </li></ul></ul><ul><li>We are drowning in data, but starving for knowledge! </li></ul><ul><li>Solution: Data warehousing and data mining </li></ul><ul><ul><li>Data warehousing and on-line analytical processing </li></ul></ul><ul><ul><li>Extraction of interesting knowledge (rules, regularities, patterns, constraints) from data in large databases </li></ul></ul>
  6. 6. Evolution of Database Technology <ul><li>1960s: </li></ul><ul><ul><li>Data collection, database creation, IMS and network DBMS </li></ul></ul><ul><li>1970s: </li></ul><ul><ul><li>Relational data model, relational DBMS implementation </li></ul></ul><ul><li>1980s: </li></ul><ul><ul><li>RDBMS, advanced data models (extended-relational, OO, deductive, etc.) and application-oriented DBMS (spatial, scientific, engineering, etc.) </li></ul></ul><ul><li>1990s —2000s : </li></ul><ul><ul><li>Data mining and data warehousing, multimedia databases, and Web databases </li></ul></ul>
  7. 7. What Is Data Mining? <ul><li>Data mining (knowledge discovery in databases): </li></ul><ul><ul><li>Extraction of interesting ( non-trivial, implicit, previously unknown and potentially useful ) information or patterns from data in large databases </li></ul></ul><ul><li>Alternative names and their “inside stories”: </li></ul><ul><ul><li>Data mining: a misnomer? </li></ul></ul><ul><ul><li>Knowledge discovery(mining) in databases (KDD), knowledge extraction, data/pattern analysis, data archeology, data dredging, information harvesting, business intelligence, etc. </li></ul></ul><ul><li>Not data mining if it </li></ul><ul><ul><li>handles only small amounts of data </li></ul></ul><ul><ul><li>retrieves data in answer to queries </li></ul></ul>
  8. 8. Why Data Mining? — Potential Applications <ul><li>Database analysis and decision support </li></ul><ul><ul><li>Market analysis and management </li></ul></ul><ul><ul><ul><li>customer relation management, market basket analysis </li></ul></ul></ul><ul><ul><li>Risk analysis and management </li></ul></ul><ul><ul><ul><li>Forecasting, quality control, competitive analysis </li></ul></ul></ul><ul><ul><li>Fraud detection and management </li></ul></ul><ul><li>Other Applications </li></ul><ul><ul><li>Text mining (news group, email, documents) and Web analysis. </li></ul></ul><ul><ul><li>Intelligent query answering </li></ul></ul>
  9. 9. Market Analysis and Management <ul><li>Where are the data sources for analysis? </li></ul><ul><ul><li>Credit card transactions, clickstreams, customer forms, shopping baskets </li></ul></ul><ul><li>Target marketing </li></ul><ul><ul><li>Clusters of “model” customers with same characteristics: interest, income level </li></ul></ul><ul><li>Determine customer purchasing patterns over time </li></ul><ul><li>Cross-market analysis </li></ul><ul><ul><li>Identify associations between product sales, use to predict purchases </li></ul></ul><ul><li>Customer profiling </li></ul><ul><ul><li>what types of customers buy what products? (clustering or classification) </li></ul></ul><ul><li>Identifying customer requirements </li></ul><ul><ul><li>identify best products for different customers, predict factors to attract new customers </li></ul></ul>
  10. 10. Other Applications <ul><li>Sports </li></ul><ul><ul><li>IBM Advanced Scout analyzed NBA game statistics (shots blocked, assists, and fouls) to gain competitive advantage for New York Knicks and Miami Heat </li></ul></ul><ul><li>Astronomy </li></ul><ul><ul><li>JPL and the Palomar Observatory discovered 22 quasars with the help of data mining </li></ul></ul><ul><li>Medical Research </li></ul><ul><ul><li>Large insurance companies use data mining to study questions such as the effectiveness of various kinds of antibiotic in reducing recurrent infections </li></ul></ul>
  11. 11. Data Mining: A KDD Process <ul><ul><li>Data mining: the core of knowledge discovery process. </li></ul></ul>Data Cleaning Data Integration Databases Data Warehouse Knowledge Task-relevant Data Selection Data Mining Pattern Evaluation
  12. 12. Steps of a KDD Process <ul><li>Learning the application domain: </li></ul><ul><ul><li>relevant prior knowledge and goals of application </li></ul></ul><ul><li>Creating a target data set: data selection </li></ul><ul><li>Data cleaning and preprocessing: (may take 60% of effort!) </li></ul><ul><li>Data reduction and transformation : </li></ul><ul><ul><li>Find useful features, dimensionality/variable reduction, invariant representation. </li></ul></ul><ul><li>Choosing functions of data mining </li></ul><ul><ul><li>summarization, classification, regression, association, clustering. </li></ul></ul><ul><li>Choosing the mining algorithm(s) </li></ul><ul><li>Data mining : search for patterns of interest </li></ul><ul><li>Pattern evaluation and knowledge presentation </li></ul><ul><ul><li>visualization, transformation, removing redundant patterns, etc. </li></ul></ul><ul><li>Use of discovered knowledge </li></ul>
  13. 13. Data Mining and Business Intelligence Increasing potential to support business decisions End User Business Analyst Data Analyst DBA Making Decisions Data Presentation Visualization Techniques Data Mining Information Discovery Data Exploration OLAP, MDA Statistical Analysis, Querying and Reporting Data Warehouses / Data Marts Data Sources Paper, Files, Information Providers, Database Systems, OLTP
  14. 14. Architecture of a Typical Data Mining System Data Warehouse Data cleaning & data integration Filtering Databases Database or data warehouse server Data mining engine Pattern evaluation Graphical user interface Knowledge-base
  15. 15. Data Mining: On What Kind of Data? <ul><li>Relational databases </li></ul><ul><li>Data warehouses </li></ul><ul><li>Transactional databases </li></ul><ul><li>Advanced DB and information repositories </li></ul><ul><ul><li>Object-oriented and object-relational databases </li></ul></ul><ul><ul><li>Spatial databases </li></ul></ul><ul><ul><li>Time-series data and temporal data </li></ul></ul><ul><ul><li>Text databases and multimedia databases </li></ul></ul><ul><ul><li>Heterogeneous and legacy databases </li></ul></ul><ul><ul><li>WWW </li></ul></ul>
  16. 16. Data Mining Functionalities (1) <ul><li>Concept description: Characterization and discrimination </li></ul><ul><ul><li>Generalize, summarize, and contrast data characteristics, e.g., dry vs. wet regions </li></ul></ul><ul><li>Association ( correlation and causality) </li></ul><ul><ul><li>Multi-dimensional vs. single-dimensional association </li></ul></ul><ul><ul><li>age(X, “20..29”) ^ income(X, “20..29K”)  buys(X, “PC”) [support = 2%, confidence = 60%] </li></ul></ul><ul><ul><li>contains(T, “computer”)  contains(x, “software”) [1%, 75%] </li></ul></ul>
  17. 17. Data Mining Functionalities (2) <ul><li>Classification and Prediction </li></ul><ul><ul><li>Finding models (functions) that describe and distinguish classes or concepts for future prediction </li></ul></ul><ul><ul><li>E.g., classify countries based on climate, or classify cars based on gas mileage </li></ul></ul><ul><ul><li>Presentation: decision-tree, classification rule, neural network </li></ul></ul><ul><ul><li>Prediction: Predict some unknown or missing numerical values </li></ul></ul><ul><li>Cluster analysis </li></ul><ul><ul><li>Class label is unknown: Group data to form new classes, e.g., cluster houses to find distribution patterns </li></ul></ul><ul><ul><li>Clustering based on the principle: maximizing the intra-class similarity and minimizing the interclass similarity </li></ul></ul>
  18. 18. Data Mining Functionalities (3) <ul><li>Outlier analysis </li></ul><ul><ul><li>Outlier: a data object that does not comply with the general behavior of the data </li></ul></ul><ul><ul><li>It can be considered as noise or exception but is quite useful in fraud detection, rare events analysis </li></ul></ul><ul><li>Trend and evolution analysis </li></ul><ul><ul><li>Trend and deviation: regression analysis </li></ul></ul><ul><ul><li>Sequential pattern mining, periodicity analysis </li></ul></ul><ul><ul><li>Similarity-based analysis </li></ul></ul><ul><li>Other pattern-directed or statistical analyses </li></ul>
  19. 19. Are All the “Discovered” Patterns Interesting? <ul><li>A data mining system/query may generate thousands of patterns, not all of them are interesting. </li></ul><ul><ul><li>Suggested approach: Human-centered, query-based, focused mining </li></ul></ul><ul><li>Interestingness measures : A pattern is interesting if it is easily understood by humans, valid on new or test data with some degree of certainty, potentially useful , novel, or validates some hypothesis that a user seeks to confirm </li></ul><ul><li>Objective vs. subjective interestingness measures: </li></ul><ul><ul><li>Objective: based on statistics and structures of patterns, e.g., support, confidence, etc. </li></ul></ul><ul><ul><li>Subjective: based on user’s belief in the data, e.g., unexpectedness, novelty, actionability, etc. </li></ul></ul>
  20. 20. Can We Find All and Only Interesting Patterns? <ul><li>Find all the interesting patterns: Completeness </li></ul><ul><ul><li>Can a data mining system find all the interesting patterns? </li></ul></ul><ul><ul><li>Association vs. classification vs. clustering </li></ul></ul><ul><li>Search for only interesting patterns: Optimization </li></ul><ul><ul><li>Can a data mining system find only the interesting patterns? </li></ul></ul><ul><ul><li>Approaches </li></ul></ul><ul><ul><ul><li>First generate all the patterns and then filter out the uninteresting ones. </li></ul></ul></ul><ul><ul><ul><li>Generate only the interesting patterns — mining query optimization </li></ul></ul></ul>
  21. 21. Data Mining: Confluence of Multiple Disciplines Data Mining Database Technology Statistics Other Disciplines Information Science Machine Learning Visualization
  22. 22. Data Mining: Classification Schemes <ul><li>General functionality </li></ul><ul><ul><li>Descriptive data mining </li></ul></ul><ul><ul><li>Predictive data mining </li></ul></ul><ul><li>Different views, different classifications </li></ul><ul><ul><li>Kinds of databases to be mined </li></ul></ul><ul><ul><li>Kinds of knowledge to be discovered </li></ul></ul><ul><ul><li>Kinds of techniques utilized </li></ul></ul><ul><ul><li>Kinds of applications adapted </li></ul></ul>
  23. 23. A Multi-Dimensional View of Data Mining Classification <ul><li>Databases to be mined </li></ul><ul><ul><li>Relational, transactional, object-oriented, object-relational, active, spatial, time-series, text, multi-media, heterogeneous, legacy, WWW, etc. </li></ul></ul><ul><li>Knowledge to be mined </li></ul><ul><ul><li>Characterization, discrimination, association, classification, clustering, trend, deviation and outlier analysis, etc. </li></ul></ul><ul><ul><li>Multiple/integrated functions and mining at multiple levels </li></ul></ul><ul><li>Techniques utilized </li></ul><ul><ul><li>Database-oriented, data warehouse (OLAP), machine learning, statistics, visualization, neural network, etc. </li></ul></ul><ul><li>Applications adapted </li></ul><ul><ul><li>Retail, telecommunication, banking, fraud analysis, DNA mining, stock market analysis, Web mining, Weblog analysis, etc. </li></ul></ul>
  24. 24. Major Issues in Data Mining (1) <ul><li>Mining methodology and user interaction </li></ul><ul><ul><li>Mining different kinds of knowledge in databases </li></ul></ul><ul><ul><li>Interactive mining of knowledge at multiple levels of abstraction </li></ul></ul><ul><ul><li>Incorporation of background knowledge </li></ul></ul><ul><ul><li>Data mining query languages and ad-hoc data mining </li></ul></ul><ul><ul><li>Expression and visualization of data mining results </li></ul></ul><ul><ul><li>Handling noise and incomplete data </li></ul></ul><ul><ul><li>Pattern evaluation: the interestingness problem </li></ul></ul><ul><li>Performance and scalability </li></ul><ul><ul><li>Efficiency and scalability of data mining algorithms </li></ul></ul><ul><ul><li>Parallel, distributed and incremental mining methods </li></ul></ul>
  25. 25. Major Issues in Data Mining (2) <ul><li>Issues relating to the diversity of data types </li></ul><ul><ul><li>Handling relational and complex types of data </li></ul></ul><ul><ul><li>Mining information from heterogeneous databases and global information systems (WWW) </li></ul></ul><ul><li>Issues related to applications and social impacts </li></ul><ul><ul><li>Application of discovered knowledge </li></ul></ul><ul><ul><ul><li>Domain-specific data mining tools </li></ul></ul></ul><ul><ul><ul><li>Intelligent query answering </li></ul></ul></ul><ul><ul><ul><li>Process control and decision making </li></ul></ul></ul><ul><ul><li>Integration of the discovered knowledge with existing knowledge: A knowledge fusion problem </li></ul></ul><ul><ul><li>Protection of data security, integrity, and privacy </li></ul></ul>
  26. 26. Summary <ul><li>Data mining: discovering interesting patterns from large amounts of data </li></ul><ul><li>A natural evolution of database technology, in great demand, with wide applications </li></ul><ul><li>A KDD process includes data cleaning, data integration, data selection, transformation, data mining, pattern evaluation, and knowledge presentation </li></ul><ul><li>Mining can be performed in a variety of information repositories </li></ul><ul><li>Data mining functionalities: characterization, discrimination, association, classification, clustering, outlier and trend analysis, etc. </li></ul><ul><li>Classification of data mining systems </li></ul><ul><li>Major issues in data mining </li></ul>
  27. 27. Where to Find References? <ul><li>Data mining and KDD: </li></ul><ul><ul><li>Conference proceedings: KDD, and others, such as PKDD, PAKDD, etc. </li></ul></ul><ul><ul><li>Journal: Data Mining and Knowledge Discovery </li></ul></ul><ul><li>Database field: </li></ul><ul><ul><li>Conference proceedings: ACM-SIGMOD, ACM-PODS, VLDB, ICDE, EDBT, DASFAA </li></ul></ul><ul><ul><li>Journals: ACM-TODS, J. ACM, IEEE-TKDE, JIIS, etc. </li></ul></ul><ul><li>AI and Machine Learning: </li></ul><ul><ul><li>Conference proceedings: Machine learning, AAAI, IJCAI, etc. </li></ul></ul><ul><ul><li>Journals: Machine Learning, Artificial Intelligence, etc. </li></ul></ul><ul><li>Statistics: </li></ul><ul><ul><li>Conference proceedings: Joint Stat. Meeting, etc. </li></ul></ul><ul><ul><li>Journals: Annals of statistics, etc. </li></ul></ul><ul><li>Visualization: </li></ul><ul><ul><li>Conference proceedings: CHI, etc. </li></ul></ul><ul><ul><li>Journals: IEEE Trans. visualization and computer graphics, etc. </li></ul></ul>
  28. 28. References <ul><li>U. M. Fayyad, G. Piatetsky-Shapiro, P. Smyth, and R. Uthurusamy. Advances in Knowledge Discovery and Data Mining. AAAI/MIT Press, 1996. </li></ul><ul><li>J. Han and M. Kamber. Data Mining: Concepts and Techniques. Morgan Kaufmann, 2000. </li></ul><ul><li>T. Imielinski and H. Mannila. A database perspective on knowledge discovery. Communications of ACM, 39:58-64, 1996. </li></ul><ul><li>G. Piatetsky-Shapiro, U. Fayyad, and P. Smith. From data mining to knowledge discovery: An overview. In U.M. Fayyad, et al. (eds.), Advances in Knowledge Discovery and Data Mining, 1-35. AAAI/MIT Press, 1996. </li></ul><ul><li>G. Piatetsky-Shapiro and W. J. Frawley. Knowledge Discovery in Databases. AAAI/MIT Press, 1991. </li></ul>
  29. 29. Data Mining for Web Sites
  30. 30. Data Mining for Web Sites <ul><li>Clickstream Mining </li></ul><ul><li>KDD Cup </li></ul><ul><li>Mining site databases </li></ul>
  31. 31. Clickstream Mining <ul><li>Kinds of data available </li></ul><ul><ul><li>Raw Data </li></ul></ul><ul><ul><li>Aggregations and Cleanup </li></ul></ul><ul><li>Kinds of questions you can ask </li></ul><ul><li>Some of the cautions </li></ul>
  32. 32. Clickstream Mining <ul><li>What is a clickstream? </li></ul><ul><ul><li>The record of every page request from every visitor to your site </li></ul></ul><ul><li>What does it typically contain? </li></ul><ul><ul><li>Date/time of the page request </li></ul></ul><ul><ul><li>IP address of visitor </li></ul></ul><ul><ul><li>Page object being requested (whole page or a frame, image, etc.) </li></ul></ul><ul><ul><li>Type of request (get, submit) </li></ul></ul><ul><ul><li>Referrer </li></ul></ul><ul><ul><li>Browser making reque st </li></ul></ul>
  33. 33. Data Cleaning <ul><li>Eliminate search engines and bots? They follow atypical patterns through a site </li></ul><ul><ul><li>Can’t typically do by IP address. </li></ul></ul><ul><ul><li>Many hits within a very short time period </li></ul></ul><ul><ul><li>exactly one hit on each link with a depth first or breadth-first pattern </li></ul></ul><ul><ul><li>Hits at the same time every day, at unusual times. </li></ul></ul><ul><li>Eliminate internal testers? </li></ul><ul><ul><li>Typically can do by IP address. Harder if both developers and customers are internal and addressing is dynamic. </li></ul></ul><ul><li>Eliminate certain sites? </li></ul><ul><ul><li>AOL reassigns IP at every request </li></ul></ul><ul><ul><li>Previous experience suggests that you get a lot of valueless hits from, e.g., the .edu domain. </li></ul></ul>
  34. 34. Aggregations/Dimensions <ul><li>Aggregate or process individual log requests to get richer dimensions </li></ul><ul><ul><li>Date and Time </li></ul></ul><ul><ul><li>Visitors </li></ul></ul><ul><ul><li>Page object </li></ul></ul><ul><ul><li>Session </li></ul></ul><ul><ul><li>Path </li></ul></ul>
  35. 35. Some Aggregations <ul><li>Date and Time </li></ul><ul><ul><li>Separate them! </li></ul></ul><ul><ul><li>Reference to standard such as GMT </li></ul></ul><ul><ul><li>If multiple servers, need very accurate synchronization </li></ul></ul><ul><li>Visitors </li></ul><ul><ul><li>anonymous, by IP only. Track within one session (probably) </li></ul></ul><ul><ul><li>Cookie. Track visitor within one session reliably, possibly across sessions </li></ul></ul><ul><ul><li>Registration. Have some significant data. Name, email address, etc. </li></ul></ul>
  36. 36. Some More Aggregations <ul><li>Page object. </li></ul><ul><ul><li>Group together objects on one “page”. Frames, images </li></ul></ul><ul><ul><li>Add meta-information/page characteristics if available. DB-based, portal-based, XML-based web-sites. </li></ul></ul><ul><li>Session </li></ul><ul><ul><li>One “visit” by a user </li></ul></ul><ul><ul><li>Typically, all connections from the same IP address without a gap of at least a certain length. </li></ul></ul><ul><ul><li>Login to logout or timeout of you require login. </li></ul></ul><ul><li>Path </li></ul><ul><ul><li>Sequence of pages visited during one session by one visitor </li></ul></ul>
  37. 37. What’s It Good For? <ul><li>Kinds of questions you can answer solely through clickstream data </li></ul><ul><ul><li>On what pages did people spend a relatively long time? </li></ul></ul><ul><ul><li>What was the last page typically viewed? Did people follow “recommender” links? </li></ul></ul><ul><ul><li>Where did referrals come from? </li></ul></ul><ul><ul><li>Where did referrals who spent significant time come from? </li></ul></ul><ul><li>Mostly questions about the web site itself </li></ul><ul><li>Mostly descriptive statistics with relatively simple analyses once the cleanup and aggregation is done </li></ul><ul><li>Interpreting the answers to the questions requires an understanding of the domain </li></ul>
  38. 38. Some cautions <ul><li>Visitor Counts: DHCP, caching, AOL </li></ul><ul><li>Session definition: false positives AND negatives </li></ul><ul><li>Path through site: caching and “go” menu </li></ul><ul><li>“Time on site”: count UP TO last request, but not time on last page. </li></ul>
  39. 39. KDD Cup <ul><li>Annual challenge problem at the ACM KDD conference. </li></ul><ul><li>In 2000, it involved clickstream mining. </li></ul><ul><li>In 2001, </li></ul><ul><ul><li>Prediction of Molecular Bioactivity for Drug Design </li></ul></ul><ul><ul><li>Prediction of Gene/Protein Function and Localization </li></ul></ul><ul><li>In 2002, </li></ul><ul><ul><li>Task 1: Information Extraction from Biomedical Articles </li></ul></ul><ul><ul><li>Task 2: Yeast Gene Regulation Prediction </li></ul></ul>
  40. 40. KDD Cup, 2000 <ul><li>Five questions: </li></ul><ul><ul><li>Given a set of page views, will the visitor view another page on the site or will the visitor leave? </li></ul></ul><ul><ul><li>Given a set of page views, which product brand will the visitor view in the remainder of the session? </li></ul></ul><ul><ul><li>Given a set of purchases over a period of time, characterize visitors who spend more than $12 (order amount) on an average order at the site. </li></ul></ul><ul><ul><li>Given a set of page views, characterize killer pages, i.e., pages after which users leave the site. </li></ul></ul><ul><ul><li>Given a set of page views, characterize which product brand a visitor will view in the remainder of the session? </li></ul></ul><ul><li> </li></ul><ul><li>http://robotics.Stanford.EDU/~ronnyk/kddCupTalk.ppt </li></ul>
  41. 41. Other Kinds of Data Mining For the Web
  42. 42. Site Databases <ul><li>Kinds of data available </li></ul><ul><li>Data cleanup and aggregation a lot easier </li></ul><ul><li>Kinds of questions you might ask </li></ul><ul><li>Recommender systems </li></ul><ul><ul><li>Collaborative filtering </li></ul></ul><ul><ul><li>Simple correlations </li></ul></ul><ul><li>Can get really fancy: Amazon </li></ul>
  43. 43. Kinds of Data Available <ul><li>User data elicited from user: </li></ul><ul><ul><li>Ordering information </li></ul></ul><ul><ul><li>Preferences, likes, dislikes </li></ul></ul><ul><ul><li>Personal information such as name, address, credit car d </li></ul></ul><ul><li>Enriched User Data (e.g., Acxiom Infobase) </li></ul><ul><ul><li>age </li></ul></ul><ul><ul><li>gender </li></ul></ul><ul><ul><li>marital status </li></ul></ul><ul><ul><li>vehicle lifestyle </li></ul></ul><ul><ul><li>own/rent </li></ul></ul><ul><li>Product Data </li></ul>
  44. 44. Kinds of Questions <ul><li>What were typical items purchased? </li></ul><ul><li>What were typical items purchased by high spenders? </li></ul><ul><li>For people who chose X, what else might they like? </li></ul><ul><ul><li>Based on known characteristics </li></ul></ul><ul><ul><li>Based on statistical patterns </li></ul></ul>
  45. 45. Combining Data <ul><li>Using just clickstream data can give you some information relevant to a website. </li></ul><ul><li>Additional questions available if you combine: </li></ul><ul><ul><li>Clickstream </li></ul></ul><ul><ul><li>Site Databases </li></ul></ul><ul><ul><li>Enriched data from other databases </li></ul></ul>
  46. 46. Kinds of Questions <ul><li>What are general characteristics of people who spend a lot of time on the site? (e.g., educational level) </li></ul><ul><li>Which pages are visited by people who actually buy? </li></ul><ul><li>Which referring sites lead to purchases, and which to “curiosity” visits? </li></ul>
  47. 47. Issues, Concerns <ul><li>Merging data </li></ul><ul><ul><li>Just about requires login. So when do you require it? </li></ul></ul><ul><ul><li>Cookies may be misleading. One user, multiple systems; one system, multiple users </li></ul></ul><ul><li>Need to know domain, to interpret results </li></ul>
  48. 48. Recommender Systems <ul><li>Very common addition to e-commerce sites </li></ul><ul><li>Editorial recommenders </li></ul><ul><li>Content Filtering Recommenders </li></ul><ul><li>Collaborative Filtering Recommenders </li></ul><ul><li>Hybrids </li></ul>
  49. 49. Editorial Filtering <ul><li>Recommendations made by a person </li></ul><ul><li>Not new, obviously </li></ul><ul><li>Web has made them much more accessible </li></ul><ul><ul><li> Movie reviews </li></ul></ul><ul><ul><li> Mystery book reviews </li></ul></ul><ul><ul><li>Search, browse capabilities </li></ul></ul><ul><li>Most prevalent for media: books, movies, CDs </li></ul><ul><li>Advantages: </li></ul><ul><ul><li>Detailed, &quot;accurate&quot; reviews. </li></ul></ul><ul><ul><li>Add context </li></ul></ul><ul><li>Disadvantages </li></ul><ul><ul><li>Coverage is limited </li></ul></ul><ul><ul><li>No personalization </li></ul></ul><ul><ul><li>Some areas (e.g., travel) heavily dominated by commercial sites </li></ul></ul>
  50. 50. Content Filtering <ul><li>Find documents &quot;like this one&quot; </li></ul><ul><li>Attributes for comparison can be </li></ul><ul><ul><li>meta-data </li></ul></ul><ul><ul><ul><li>author </li></ul></ul></ul><ul><ul><ul><li>subject </li></ul></ul></ul><ul><ul><ul><li>director </li></ul></ul></ul><ul><ul><li>These are typically simple statistics </li></ul></ul><ul><ul><li>document content </li></ul></ul><ul><ul><ul><li>bag-of-words, vectors </li></ul></ul></ul><ul><ul><ul><li>keywords </li></ul></ul></ul><ul><ul><li>All the categorization techniques we have discussed </li></ul></ul>
  51. 51. Collaborative Filtering <ul><li>DB of user ratings/preferences. Explicit or inferred from purchases </li></ul><ul><li>For case to be predicted or recommended </li></ul><ul><ul><li>Determine nearest neighbors based on known shared data </li></ul></ul><ul><ul><li>Weight neighbors’ choices based on “nearness”. </li></ul></ul><ul><ul><li>Return top predictions or recommendatio ns </li></ul></ul><ul><li>Can use other algorithms for choosing cases to predict from. (e.g., neural nets) </li></ul><ul><ul><li>All assume some dimensions on which we have (probably incomplete) data for each case. </li></ul></ul><ul><ul><li>All are automatic, not involving human judgment </li></ul></ul><ul><li>Lyle Ungar has an excellent set of links: </li></ul>
  52. 52. Amazon recommender systems <ul><li>Rich set of recommendations using multiple techniques </li></ul><ul><li>Content Filtering: Books like this, authors like this: straight descriptive statistics. (Caution: control for overall frequency?) </li></ul><ul><li>Collaborative filtering: individual recommendations, based on purchases and ratings </li></ul><ul><li>Editorial Filtering: Lists provided by users. </li></ul><ul><li>Hybrid: Best Seller lists, current rank of books. </li></ul><ul><li>Access recommender system directly: </li></ul><ul><ul><ul><li>I own it </li></ul></ul></ul><ul><ul><ul><li>Rate it </li></ul></ul></ul><ul><ul><ul><li>Not interested </li></ul></ul></ul><ul><ul><ul><li>exclude this item </li></ul></ul></ul><ul><ul><ul><li>why was this recommended? </li></ul></ul></ul>
  53. 53. Tuning Amazon's Recommender System <ul><li>Individual recommendations are based on purchases and ratings. </li></ul><ul><li>Access recommender system directly: </li></ul><ul><ul><ul><li>I own it </li></ul></ul></ul><ul><ul><ul><li>Rate it </li></ul></ul></ul><ul><ul><ul><li>Not interested </li></ul></ul></ul><ul><ul><ul><li>exclude this item </li></ul></ul></ul><ul><ul><ul><li>add this item </li></ul></ul></ul><ul><li>Why was this recommended? </li></ul>
  54. 54. Web Privacy
  55. 55. Introduction <ul><li>Privacy is a significant issue </li></ul><ul><ul><li>On the web </li></ul></ul><ul><ul><ul><li>Who knows what about you? </li></ul></ul></ul><ul><ul><ul><li>What are they doing with it </li></ul></ul></ul><ul><ul><li>For data mining </li></ul></ul><ul><ul><ul><li>Who has collected data on you (not just on the web) </li></ul></ul></ul><ul><ul><ul><li>Why did they collect it? </li></ul></ul></ul><ul><ul><ul><li>What else are they entitled to do with it? </li></ul></ul></ul><ul><li>Who owns data about you? </li></ul><ul><li>How can society best control privacy abuses? </li></ul><ul><ul><li>Voluntary compliance and market forces? </li></ul></ul><ul><ul><li>Government regulation? </li></ul></ul>
  56. 56. Homework Assignment <ul><li>1 . How many clicks from the home page did it take you to reach the privacy policy? </li></ul><ul><li>2. What information do they collect? For what is it used? </li></ul><ul><li>3. With whom do they share information? </li></ul><ul><li>4. If they change their policy how are you notified? </li></ul><ul><li>5. Can you ask that information maintained be limited? How? </li></ul><ul><li>6. Can you see what information is maintained about you? Ask that information be removed? Ask that it be corrected? How? </li></ul>
  57. 57. Who Knows What about You? <ul><li>Clickstreams and </li></ul><ul><li>Cookies </li></ul><ul><li>Brief overview of some of what’s out there, just to get you thinking :-) </li></ul><ul><li> </li></ul><ul><li> </li></ul>
  58. 58. How Do We Control It? <ul><li>The US has tended toward technical, marketplace and voluntary standards. </li></ul><ul><ul><li>Patchwork of state and local laws. </li></ul></ul><ul><ul><li>Several laws proposed at the national level, but none has passed </li></ul></ul><ul><ul><li>Serious Freedom of Speech concerns, both directions </li></ul></ul><ul><ul><li>Much industrial pressure to keep voluntary </li></ul></ul><ul><li>The European Union has passed the EU Data Privacy Directive. </li></ul><ul><ul><li>Articles 25 and 26 prohibit exchanging data with countries which do not comply </li></ul></ul><ul><ul><li> </li></ul></ul><ul><li>U.S.has proposed a Safe Harbor </li></ul><ul><ul><li>register and be certified as complying with safe harbor provisions </li></ul></ul><ul><ul><li>If certified, acceptable as alternative for EU data exchange </li></ul></ul><ul><ul><li> </li></ul></ul>
  59. 59. Safe Harbor Provisions <ul><li>In place </li></ul><ul><li>Gradually being adopted; 156 organizations listed, compared to 30 a year ago. </li></ul><ul><li>Continues to be debated; 156 is miniscule! </li></ul><ul><li>Both enforcement of Safe Harbor compliance and EU enforcement still issues </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul>
  60. 60. Safe Harbor Provisions <ul><li>Notice </li></ul><ul><li>Choice </li></ul><ul><li>Onward Transfer (Transfers to Third Parties) </li></ul><ul><li>Access </li></ul><ul><li>Security </li></ul><ul><li>Data integrity </li></ul><ul><li>Enforcement </li></ul>
  61. 61. Notice <ul><li>Notice: Organizations must notify individuals about the purposes for which they collect and use information about them. They must provide information about how individuals can contact the organization with any inquiries or complaints, the types of third parties to which it discloses the information and the choices and means the organization offers for limiting its use and disclosure. </li></ul>
  62. 62. Choice <ul><li>Choice: Organizations must give individuals the opportunity to choose (opt out) whether their personal information is to be disclosed to a third party or to be used for a purpose incompatible with the purpose for which it was originally collected or subsequently authorized by the individual. For sensitive information, affirmative or explicit (opt in) choice must be given if the information is to be disclosed to a third party or used for a purpose other than its original purpose or the purpose authorized subsequently by the individua l. </li></ul>
  63. 63. Onward Transfer <ul><li>Onward Transfer (Transfers to Third Parties): To disclose information to a third party, organizations must apply the notice and choice principles. Where an organization wishes to transfer information to a third party that is acting as an agent (1) , it may do so if it makes sure that the third party subscribes to the safe harbor principles or is subject to the Directive or another adequacy finding. As an alternative, the organization can enter into a written agreement with such third party requiring that the third party provide at least the same level of privacy protection as is required by the relevant principles. </li></ul>
  64. 64. Access <ul><li>Access: Individuals must have access to personal information about them that an organization holds and be able to correct, amend, or delete that information where it is inaccurate, except where the burden or expense of providing access would be disproportionate to the risks to the individual's privacy in the case in question, or where the rights of persons other than the individual would be violated. </li></ul>
  65. 65. Security <ul><li>Security: Organizations must take reasonable precautions to protect personal information from loss, misuse and unauthorized access, disclosure, alteration and destruction. </li></ul>
  66. 66. Data Integrity <ul><li>Data integrity: Personal information must be relevant for the purposes for which it is to be used. An organization should take reasonable steps to ensure that data is reliable for its intended use, accurate, complete, and current. </li></ul>
  67. 67. Enforcement <ul><li>Enforcement: In order to ensure compliance with the safe harbor principles, there must be (a) readily available and affordable independent recourse mechanisms so that each individual's complaints and disputes can be investigated and resolved and damages awarded where the applicable law or private sector initiatives so provide; (b) procedures for verifying that the commitments companies make to adhere to the safe harbor principles have been implemented; and (c) obligations to remedy problems arising out of a failure to comply with the principles. Sanctions must be sufficiently rigorous to ensure compliance by the organization. Organizations that fail to provide annual self certification letters will no longer appear in the list of participants and safe harbor benefits will no longer be assured. </li></ul>
  68. 68. What do YOU think? <ul><li>Do you think the policy for your web pages is adequately described? Reasonable? </li></ul><ul><li>How you would implement privacy as a web designer? </li></ul><ul><li>What are your concerns as a web user? </li></ul>