Web Clustering and Text Categorization -- MP-Boost: A Multiple-Pivot Boosting Algorithm and Its Application to Text Categorization -- TreeBoost.MH: A Boosting Algorithm for Multi-label Hierarchical Text Categorization -- Cluster Generation and Cluster Labelling for Web Snippets: A Fast and Accurate Hierarchical Solution -- Principal Components for Automatic Term Hierarchy Building -- Strings -- Computing the Minimum Approximate ?-Cover of a String -- Sparse Directed Acyclic Word Graphs -- On-Line Repetition Detection -- User Behavior -- Analyzing User Behavior to Rank Desktop Items -- The Intention Behind Web Queries -- Web Search Algorithms -- Compact Features for Detection of Near-Duplicates in Distributed Retrieval -- Inverted Files Versus Suffix Arrays for Locating Patterns in Primary Memory -- Efficient Lazy Algorithms for Minimal-Interval Semantics -- Output-Sensitive Autocompletion Search -- Compression -- A Compressed Self-index Using a Ziv-Lempel Dictionary -- Mapping Words into Codewords on PPM -- Correction -- Improving Usability Through Password-Corrective Hashing -- Word-Based Correction for Retrieval of Arabic OCR Degraded Documents -- Information Retrieval Applications -- A Statistical Model of Query Log Generation -- Using String Comparison in Context for Improved Relevance Feedback in Different Text Media -- A Multiple Criteria Approach for Information Retrieval -- English to Persian Transliteration -- Bio Informatics -- Efficient Algorithms for Pattern Matching with General Gaps and Character Classes -- Matrix Tightness: A Linear-Algebraic Framework for Sorting by Transpositions -- How to Compare Arc-Annotated Sequences: The Alignment Hierarchy -- Web Search Engines -- Structured Index Organizations for High-Throughput Text Querying -- Adaptive Query-Based Sampling of DistributedCollections -- Short Papers -- Dotted Suffix Trees A Structure for Approximate Text Indexing -- Phrase-Based Pattern Matching in Compressed Text -- Discovering Context-Topic Rules in Search Engine Logs -- Incremental Aggregation of Latent Semantics Using a Graph-Based Energy Model -- A New Algorithm for Fast All-Against-All Substring Matching.

This volume contains the papers presented at the 13th International Symposium on String Processing and Information Retrieval (SPIRE), held October 11-13, 2006, in Glasgow, Scotland. The SPIRE annual symposium provides an opportunity for both new and established researchers to present original contributions to areas such as string processing (dictionary algorithms, text searching, pattern matching, text c- pression, text mining, natural language processing, and automata-based string processing); information retrieval languages, applications, and evaluation (IR modelling, indexing, ranking and ?ltering, interface design, visualization, cro- lingual IR systems, multimedia IR, digital libraries, collaborative retrieval, W- related applications, XML, information retrieval from semi-structured data, text mining, and generation of structured data from text); and interaction of biology and computation (sequencing and applications in molecular biology, evolution and phylogenetics, recognition of genes and regulatory elements, and sequen- driven protein structure prediction). The papers in this volume were selected from 102 papers submitted from over 20 di?erent countries in response to the Call for Papers. A total of 26 submissions were accepted as full papers, yielding an acceptance rate of about 25%. In view of the large number of good-quality submissions the Program Committee decided to accept 5 short papers, that have also been included in the proceedings. SPIRE 2006 also featured two talks by invited speakers: Jamie Callan (Carnegie Mellon University, USA) and Martin Farach-Colton (Rutgers University, USA).