Web mining
Web mining is the application of data mining techniques to discover patterns from the World Wide Web. It uses automated methods to extract both structured and unstructured data from web pages, server logs and link structures. There are three main sub-categories of web mining. Web content mining extracts information from within a page. Web structure mining discovers the structure of the hyperlinks between documents, categorizing sets of web pages and measuring the similarity and relationship between different sites. Web usage mining finds patterns of usage of web pages. Web mining types. Web mining can be divided into  three different types – Web usage mining, Web content mining and Web structure mining. Web usage mining. Web usage mining is the application of data mining techniques to discover interesting usage patterns from Web data in order to understand and better serve the needs of Web-based applications. Usage data captures the identity or origin of Web users along with their browsing behavior at a Web site. Web usage mining itself can be classified further depending on the kind of usage data considered: Studies related to work are concerned with two areas: constraint-based data mining algorithms applied in Web usage  mining and developed software tools (systems). Costa and Seco demonstrated that web log mining can be used to extract semantic information (hyponymy relationships in particular) about the user and a given community. Pros. Web usage mining essentially has many advantages which makes this technology attractive to corporations including government agencies. This technology has enabled e-commerce to do personalized marketing, which eventually results in higher trade volumes. Government agencies are using this technology to classify threats and fight against terrorism. The predicting capability of mining applications can benefit society by identifying criminal activities. Companies can establish better customer relationship by  understanding the needs of the customer better and reacting to customer needs faster. Companies can find, attract and retain customers; they can save on production costs by utilizing the acquired insight of customer requirements. They can increase profitability by target pricing based on the profiles created. They can even find customers who might default to a competitor the company will try to retain the customer by providing promotional offers to the specific customer, thus reducing the risk of losing a customer or customers. More benefits of web usage mining, particularly in the area of personalization, are outlined in specific frameworks  such as the probabilistic latent semantic analysis model, which offer additional features to the user behavior and access pattern. This is because the process provides the user with more relevant content through collaborative recommendation. These models also demonstrate a capability in web usage mining technology to address problems associated with traditional techniques such as biases and questions regarding validity since the data and patterns obtained are not subjective and do not degrade over time. There are also elements unique to web usage mining that can show the technology's benefits and these include the way semantic knowledge is applied when  interpreting, analyzing, and reasoning about usage patterns during the mining phase. Cons. Web usage mining by itself does not create issues, but this technology when used on data of personal nature might cause concerns. The most criticized ethical issue involving web usage mining is the invasion of privacy. Privacy is considered lost when information concerning an individual is obtained, used, or disseminated, especially if this occurs without the individual's knowledge or consent. The obtained data will be analyzed, made anonymous, then clustered to form anonymous profiles. These applications de-individualize users by judging them by their mouse clicks rather  than by identifying information. De-individualization in general can be defined as a tendency of judging and treating people on the basis of group characteristics instead of on their own individual characteristics and merits. Another important concern is that the companies collecting the data for a specific purpose might use the data for totally different purposes, and this essentially violates the user's interests. The growing trend of selling personal data as a commodity encourages website owners to trade personal data obtained from their site. This trend has increased the amount of data being captured and traded increasing the likeliness  of one's privacy being invaded. The companies which buy the data are obliged make it anonymous and these companies are considered authors of any specific release of mining patterns. They are legally responsible for the contents of the release; any inaccuracies in the release will result in serious lawsuits, but there is no law preventing them from trading the data. Some mining algorithms might use controversial attributes like sex, race, religion, or sexual orientation to categorize individuals. These practices might be against the anti-discrimination legislation. The applications make it hard to identify the use of such controversial attributes , and there is no strong rule against the usage of such algorithms with such attributes. This process could result in denial of service or a privilege to an individual based on his race, religion or sexual orientation. This situation can be avoided by the high ethical standards maintained by the data mining company. The collected data is being made anonymous so that, the obtained data and the obtained patterns cannot be traced back to an individual. It might look as if this poses no threat to one's privacy, however additional information can be inferred by the application by  combining two separate unscrupulous data from the user. Web structure mining. Web structure mining uses graph theory to analyze the node and connection structure of a web site. According to the type of web structural data, web structure mining can be divided into two kinds: Web structure mining terminology: An example of a techniques of web structure mining is the PageRank algorithm used by Google to rank search results. The rank of a page is decided by the number and quality of links pointing to the target node. Web content mining. Web content mining is the mining, extraction and integration  of useful data, information and knowledge from Web page content. The heterogeneity and the lack of structure that permits much of the ever-expanding information sources on the World Wide Web, such as hypertext documents, makes automated discovery, organization, and search and indexing tools of the Internet and the World Wide Web such as Lycos, Alta Vista, WebCrawler, Aliweb, MetaCrawler, and others provide some comfort to users, but they do not generally provide structural information nor categorize, filter, or interpret documents. These factors have prompted researchers to develop more intelligent tools for information retrieval, such as intelligent web agents, as  well as to extend database and data mining techniques to provide a higher level of organization for semi-structured data available on the web. The agent-based approach to web mining involves the development of sophisticated AI systems that can act autonomously or semi-autonomously on behalf of a particular user, to discover and organize web-based information. Web content mining is differentiated from two different points of view: Information Retrieval View and Database View. summarized the research works done for unstructured data and semi-structured data from information retrieval view. It shows that most of the researches use bag  of words, which is based on the statistics about single words in isolation, to represent unstructured text and take single word found in the training corpus as features. For the semi-structured data, all the works utilize the HTML structures inside the documents and some utilized the hyperlink structure between the documents for document representation. As for the database view, in order to have the better information management and querying on the web, the mining always tries to infer the structure of the web site to transform a web site to become a database. There are several ways to represent  documents; vector space model is typically used. The documents constitute the whole vector space. This representation does not realize the importance of words in a document. To resolve this, tf-idf (Term Frequency Times Inverse Document Frequency) is introduced. By multi-scanning the document, we can implement feature selection. Under the condition that the category result is rarely affected, the extraction of feature subset is needed. The general algorithm is to construct an evaluating function to evaluate the features. As feature set, information gain, cross entropy, mutual information, and odds ratio are usually used. The classifier and pattern analysis methods  of text data mining are very similar to traditional data mining techniques. The usual evaluative merits are classification accuracy, precision and recall and information score. Web mining can complement the retrieval of structured data transmitted with open protocols like OAI-PMH: an example is the aggregation of works from academic publications, which are mined to identify open access versions through a mix of open source and open data methods by academic databases like Unpaywall. Web content mining in foreign languages. Chinese. The language code of Chinese words is very complicated compared to that of English. The GB, Big5 and HZ  code are common Chinese word codes in web documents. Before text mining, one needs to identify the code standard of the HTML documents and transform it into inner code, then use other data mining techniques to find useful knowledge and useful patterns.