Information Retrieval - Academic Year 2014/2015

General Information

Teacher : Paolo Ferragina
Course ID: 289AA
CFU: 6 (first semester)
Language: English
Lectures Schedule: tuesday 14-16 (N1), thursday 14-16 (C)
Question time: by appointment.
Official Lecture's Log: Here it is the registro.
News about this course will be distributed via a Tweeter-channel

Goals

Study, design and analysis of IR systems which are efficient and effective to process, mine, search, cluster and classify documents, coming from textual, html or XML data collections. In particular, we will:

describe the main components of a modern search engine: Crawler, Parser, Compressor, Indexer, Query resolver, Results Ranker, Results Classifier/Clusterer;

present and use in the Lab some interesting Open-Source Tools for IR applications, such as Lucene and Web graph;

introduce some basic algorithmic techniques which are now ubiquitous in any IR application for data classification, compression, clustering, projection, and sketching.

Exam

The exam will consist of a written test, plus an oral discussion on the exercises.

Date	Room	Text
16-01-2015	C1	text
09-02-2015	A1	text
05-06-2015	L1	text
29-06-2015	L1	text
20-07-2015	L1	text
10-09-2015	L1	text

Books

[MRS] C.D. Manning, P. Raghavan, H. Schutze. Introduction to Information Retrieval. Cambridge University Press, 2008. [ link ]
[MG] Chapter 2 “Text compression” of Managing Gigabytes, I.H. Witten and A. Moffat and T.C. Bell, Morgan Kauffman, 1999.

Content of the Lectures

Date	Argument	Refs
23-09-2014	Introduction to the course: modern IR, not just search engines! Boolean retrieval model. Matrix document-term. Inverted list: dictionary + postings. How to implement an AND, OR and NOT queries, and their time complexities.	Slides and Chapt 1 of [MRS]
25-09-2014	The issue of hierarchical memories: I/O-model. Parsing: tokenization, normalization, lemmatization, stemming, thesauri. Statistical properties of texts: Zipf law: classical and generalized, Heaps law, Luhn's consideration.	Sect. 2.1, 2.2 and 5.1 of [MRS]. Slides of this week.
30-09-2014	Index construction: multi-way mergesort, BSBI and SPIMI. Distributed and dynamic indexing.	Chapter 4 of [MRS]. Slides.
02-10-2014	Query processing: skip pointers (with solution based on dynamic programming), caching, phrase queries.	Slides
07-10-2014	Wild-card queries (permuterm, k-gram). Edit distance: kgram index, dynamic programming. Case of 1-error. Zone indexes.	Chapter 4 and Sect. 3.2 and 3.3 of [MRS]. Slides
14-10-2014	Exact search: hashing with chaining, univeral hashing, cuckoo hashing. Prefix search: compacted trie, front coding, 2-level indexing. Exact searching with errors: Bloom filter.	Paper on cuckoo, just description (no proof). Paper on bloom filter (just things looked in class). Slides.
16-10-2014	Auto-completion search: definition, trie, top-k, cartesian tree, RMQ.	Slides. You should read Sect 8.4.1 and Sect 2 and 3 of this paper.
21-10-2014	Notion of Entropy and prefix-free codes. Huffman and Arithmetic coding, with comparisons with Entropy and comment on their performance.	Sect. 6.1 of [MRS]. Read pag. 21-36, 52-56 of [MG]. Slides.
28-10-2014	Arithmetic coding: bound on the code length, relation with entropy. LZ77, LZSS, gzip and snappy. Posting list compression, codes: gamma, delta, variable bytes.	Sez 5.3 of [MRS] and pag. 74-79 of [MG].
30-10-2014	PForDelta. Rank and Select primitives: definition and their use. Elias-Fano code and its use for postings compression.	Slides.
11-11-2014	More on Rank and Select on binary arrays. Rank and Select on general arrays: the Wavelet Tree. Binary tree encoding and navigation.	Slides
13-11-2014	Suffix arrays: data structure and search operations. Text mining over suffix arrays. Move-to-Front and Run-length-encoding and Burrows-Wheeler Transform: bzip, how to construct, how to decompress entirely or just a substring.	Slides
18-11-2014	Text-based ranking: dice, jaccard, tf-idf. Vector space model. Storage of tf-idf and use for computing document-query similarity. Fast top-k retrieval: high idf, champion lists, many query-terms, fancy hits, clustering. Relevance feedback, Rocchio, pseudo-relevance feedback, query expansion.	Sect 6.2, 6.3 from [MRS]. Chap 7 and 9 from [MRS]. Slides
25-11-2014	Link-based ranking: pagerank and HITS and weighted variants.	Chap 21 from [MRS]. Slides.
27-11-2014	Web search engines: difficulties for their design, the web-graph and its properties, how to compute the SCC I/O-efficiently, the size of the web and the estimation of the relative sizes of SE.	Chap. 8, 19.1 and 19.2, 19.5 from [MRS]. Slides
28-11-2014	The storage of the web graph. Latent Semantic Indexing.	Chap 18 and 20.4 from [MRS]. Slides.
02-12-2014	Random projections. Crawling and consistent hashing.	Chap 20.1, 20.2 and 20.3. Slides.
03-12-2014	Recommendation systems and Web advertising.	Slides.
04-12-2014	Semantic-annotation tools: basics and TAGME.
09-12-2014	Semantic-annotation tools: advanced and some applications.	Slides
10-12-2014	Extra lecture: 9-11, M1: Clustering: flat, hierarchical, soft, hard. K-means, optimal bisect, hierarchical - max, min, avg, centroid.	Chap 16 and 17 of [MRS], slides.
11-12-2014	Exercises
12-12-2014	Q&A time on theory and exercises
16-12-2014	Exercises
18-12-2014	Q&A time on theory and exercises (meeting requested by students)