(a) In ordinary English text, the average number of characters per word is 4.5. After indexing, the average length of a dictionary word is 8 characters. Suppose an index has a dictionary with 200,000 words. Assume each character occupies one byte.

(i) Explain why the average number of characters per word in ordinary English text is smaller than that in index dictionary.

(ii) With index compression, the compressed index stores dictionary as a string with block size of 4 . Estimate the size usage in number of bytes of this dictionary.

(b) A social media company runs a platform that is similar to Facebook or Twitter. Users can post freestyle messages online and their followers or friends can view the messages immediately. However, users are not allowed to comment on messages. The company has consulted you to develop a search engine to index and search for the user posted messages.

(i) With reference to the messages posted on either Facebook or Twitter, what are the potential challenges in developing this

(ii) The company explicitly requests for fast response from the search engine and accepts relatively lower quality top K results from the search engine. Briefly describe THREE (3) techniques that can be used to satisfy companys request.

(c) When a user issues a query application from submission, a search engine returns: do you mean application form submission? Discuss how to detect such kind of errors in query and how to give suggestions of correction.

(d) Briefly describe static summary and dynamic summary in the context of Web search engine.