Information Retrieval - Academic Year 2015/2016

General Information

Teacher : Paolo Ferragina
Course ID: 289AA
CFU: 6 (first semester)
Language: English
Lectures Schedule: tuesday 09-11 (N1), thursday 09-11 (A1)
Question time: after lectures (Tue/Thur 11-13).
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 as well as any unstructured domain. In the lectures, we will:

study and analyze the main components of a modern search engine: Crawler, Parser, Compressor, Indexer, Query resolver, Query and Document annotator, Results Ranker;

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

describe few other IR tools which are used either as a component of a search engine or as independent tools and build up the previous algorithmic techniques, such as: Classification, Clustering, Recommendation, Compressed Storage, Approximate indexing.

Exam

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

Date	Room	Text
11/01/2016	L1 (9:00)	text
01/02/2016	L1 (9:00)	text
27/06/2016	L1 (9:00)	text
19/07/2016	L1 (9:00)	no participants
02/09/2016	L1 (9:30)	text

Books

[MRS] C.D. Manning, P. Raghavan, H. Schutze. Introduction to Information Retrieval. Cambridge University Press, 2008. [ link ]
Some notes by Prof. Paolo Ferragina.

Content of the Lectures

Date	Argument	Refs
22/09/2015	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. The structure of a search engine.	Slides Chapt 1 of [MRS]
24/09/2015	Web search engine: difficulties in their design and their ephocs. The Web graph: some useful structural properties (such as Bow Tie). Crawling: problems and algorithmic structure. An example: Mercator.	Slides, Sections 19.1, 19.2, 19.4, 20.1, 20.2 of [MRS].
29/09/2015	Few useful algorithmic techniques for crawling the Web (and not only that!): Bloom Filter and Consistent Hashing.	Slides. Sect 20.3 and 20.4 of [MRS]. For doubts on Bloom Filter see paper.
01/10/2015	Compressed storage of the Web graph. Compressed storage of documents: LZ-based compression.	Slides, Sect 19.1 and 19.2 of [MRS], and Sect 1.1 and 2.2 of Ferragina's notes.
06/10/2015	MTF (with proof of its 2-optimality), RLE, and the Burrows-Wheeler Transform with bzip.	Slides of the previous lecture, Sect 2.1 and 2.3 of Ferragina's notes above.
08/10/2015	Storage and Transmission of single/group of file(s): Delta compression (Zdelta), File Synchronization (rsync, zsync), and Set Reconciliation.	Slides.
13/10/2015	Parsing: tokenization, normalization, lemmatization, stemming, thesauri. Statistical properties of texts: Zipf law: classical and generalized, Heaps law, Luhn's consideration.	Slides. Sect. 2.1, 2.2 and 5.1 of [MRS].
15/10/2015	The issue of hierarchical memories: I/O-model. Index construction: multi-way mergesort, BSBI and SPIMI. Sketch on MapReduce. Distributed indexing: Term-based vs Doc-based partitioning.	Slides. Chapter 4 of [MRS].
20/10/2015	Dynamic indexing. Posting list compression, codes: gamma, delta, variable bytes. PForDelta.	Slides. Sez 5.3 of [MRS] and Ferragina's notes (only the coders presented in class).
22/10/2015	Exact search: hashing with chaining, univeral hashing, cuckoo hashing. Prefix search: compacted trie, front coding, 2-level indexing. Edit distance via brute-force approach, or Dynamic Programming (possibly weighted)	Slides.
27/10/2015	Overlap measure with k-gram index. Edit distance with k-gram index. One-error match. Wild-card queries (permuterm, k-gram). Phonetic match. Context-sensitive match.	Slides. Chap 3 of [MRS].
29/10/2015	Query processing: skip pointers (with solution based on dynamic programming), caching, phrase queries. Zone index and tiered index.	Slide. Sect. 2.3 and 2.4 of [MRS]
10/11/2015	The auto-complete problem and its solutions for the top-1, top-2, .., top-k strings. Rank/Select data structures: B untouched and Elias-Fano's approach with B compressed.	Slide
12/11/2015	Exercises.
13/11/2015	Text-based ranking: dice, jaccard, tf-idf. Vector space model. Storage of tf-idf and use for computing document-query similarity. Other exercises.	Sect 6.2 and 6.3 from [MRS].
17/11/2015	Fast top-k retrieval: high idf, champion lists, many query-terms, fancy hits, clustering. Relevance feedback, Rocchio, pseudo-relevance feedback, query expansion.	Slides. Chap 7 and 9 of [MRS]
19 and 20 11/2015	Lab on Lucene. You need to configure your laptop as follows: Linux system (may be a virtual machine) with debian-like OS (e.g. `Ubuntu 15.10`), working Internet connection from the Polo's room, at least 5GB of free disk and 2GB RAM, `httrack` and `pylucene` installed (that can be done with `sudo apt-get update` and `sudo apt-get install python-lucene httrack`). In collaboration with Marco Cornolti ([email protected]).	Slides (crawling) Slides (Lucene)
24/11/2015	Performance measures: precision, recall, F1 and user happiness. Random Walks. Link-based ranking: pagerank and personalized pagerank.	Slides. Chap 8 and 21 from [MRS].
26/11/2015	CoSim Rank and HITS. Recommendation systems and Web advertising.	Slides only.
27/11/2015	Projections to smaller spaces: Latent Semantic Indexing (LSI). Random Projections: Johnson-Linderstauss Lemma and its applications.	Slides. Chap 18 from [MRS].
01/12/2015	Semantic-annotation tools: basics, Wikipedia structure, TAGME and other annotators. How to evaluate those systems. Various approaches to text representation.	Slides.
03/12/2015	More on topics annotators and their applications. Clustering: flat, hierarchical, soft, hard. K-means, optimal bisect, hierarchical - max, min, avg, centroid.	Slides. Chap 16 and 17 of [MRS].
10/12/2015	Locality-sensitive hashing: basics, hamming distance, Jaccard similarity, sketch of the main theorem.	Slides. Sect 19.6 of [MRS]
11/12/2015	Exercise
15/12/2015	Exercise