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This volume constitutes the thoroughly refereed proceedings of the 49th International Workshop on Graph-Theoretic Concepts in Computer Science, WG 2023. The 33 full papers presented in this volume were carefully reviewed and selected from a total of 116 submissions. The WG 2022 workshop aims to merge theory and practice by demonstrating how concepts from graph theory can be applied to various areas in computer science, or by extracting new graph theoretic problems from applications.

This book constitutes the refereed post-conference proceedings of the Special Event on the Analysis of Experimental Algorithms, SEA² 2019, held in Kalamata, Greece, in June 2019.The 35 revised full papers presented were carefully reviewed and selected from 45 submissions. The papers cover a wide range of topics in both computer science and operations research/mathematical programming. They focus on the role of experimentation and engineering techniques in the design and evaluation of algorithms, data structures, and computational optimization methods.

This LNCS 13453 constitutes the thoroughly refereed proceedings of the 48th International Workshop on Graph-Theoretic Concepts in Computer Science, WG 2022.The 32 full papers presented in this volume were carefully reviewed and selected from a total of 96 submissions. The WG 2022 workshop aims to merge theory and practice by demonstrating how concepts from Graph Theory can be applied to various areas in Computer Science, or by extracting new graph theoretic problems from applications.

This book constitutes revised selected papers from the 25th International Symposium on Graph Drawing and Network Visualization, GD 2017, held in Boston, MA, USA, in September 2017.The 34 full and 9 short papers presented in this volume were carefully reviewed and selected from 87 submissions. Also included in this book are 2 abstracts of keynote presentations, 16 poster abstracts, and 1 contest report. The papers are organized in topical sections named: straight-line representations; obstacles and visibility; topological graph theory; orthogonal representations and book embeddings; evaluations; tree drawings; graph layout designs; point-set embeddings; special representations; and beyond planarity.

This book constitutes the revised selected papers of the 43rd International Workshop on Graph-Theoretic Concepts in Computer Science, WG 2017, held in Eindhoven, The Netherlands, in June 2017.The 31 full papers presented in this volume were carefully reviewed and selected from 71 submissions. They cover a wide range of areas, aiming at connecting theory and applications by demonstrating how graph-theoretic concepts can be applied in various areas of computer science. Another focus is on presenting recent results and on identifying and exploring promising directions of future research.

This book constitutes the thoroughly refereed post-conference proceedings of the 9th International Conference on Computers and Games, CG 2016, held in Leiden, The Netherlands,in conjunction with the 19th Computer Olympiad and the 22nd World Computer-Chess Championship.The 20 papers presented were carefully reviewed and selected of 30 submitted papers. The 20 papers cover a wide range of computer games and many different research topics in four main classes which determined the order of publication: Monte Carlo Tree Search (MCTS) and its enhancements (seven papers), concrete games (seven papers), theoretical aspects and complexity (five papers) and cognition model (one paper). The paper Using Partial Tablebases in Breakthrough by Andrew Isaac and Richard Lorentz received the Best Paper Award.

This book constitutes revised selected papers from the 24th International Symposium on Graph Drawing and Network Visualization, GD 2016, held in Athens, Greece, in September 2016. The 45 papers presented in this volume were carefully reviewed and selected from 99 submissions. They were organized in topical sections named: large graphs and clutter avoidance; clustered graphs; planar graphs, layered and tree drawings; visibility representations; beyond planarity; crossing minimization and crossing numbers; topological graph theory; special graph embeddings; dynamic graphs, contest report.

This book constitutes the thoroughly refereed post-conference proceedings of the 18th Japanese Conference on Discrete and Computational Geometry and Graphs, JDCDGG 2015, held in Kyoto, Japan, in September 2015. The total of 25 papers included in this volume was carefully reviewed and selected from 64 submissions. The papers feature advances made in the field of computational geometry and focus on emerging technologies, new methodology and applications, graph theory and dynamics. This proceedings are dedicated to Naoki Katoh on the occasion of his retirement from Kyoto University.

This book constitutes revised selected papers from the 42nd International Workshop on Graph-Theoretic Concepts in Computer Science, WG 2016, held in Istanbul, Turkey, in June 2016. The 25 papers presented in this volume were carefully reviewed and selected from 74 submissions.The WG conferences aim to connect theory and practice by demonstrating how graph-theoretic concepts can be applied to various areas of computer science and by extracting new graph problems from applications. Their goal is to present new research results and to identify and explore directions of future research.

This book constitutes revised selected papers from the 41st International Workshop on Graph-Theoretic Concepts in Computer Science, WG 2015, held in Garching, Germany, in June 2015. The 32 papers presented in this volume were carefully reviewed and selected from 79 submissions. They were organized in topical sections named: invited talks; computational complexity; design and analysis; computational geometry; structural graph theory; graph drawing; and fixed parameter tractability.

This book constitutes the thoroughly refereed post-conference proceedings of the First IFIP WG 1.8 International Conference on Topics in Theoretical Computer Science, held in Tehran, Iran, in August 2015. The 10 full papers presented together with 3 invited talks were carefully reviewed and selected from 48 submissions. The papers feature novel and high-quality research in all areas of theoretical computer science.

This book constitutes the proceedings of the 23rd International Symposium on Graph Drawing and Network Visualization, GD 2015, held in Los Angeles, Ca, USA, in September 2015. The 35 full papers presented together with 7 short papers and 8 posters in this volume were carefully reviewed and selected from 77 submissions. Graph Drawing is concerned with the geometric representation of graphs and constitutes the algorithmic core of Network Visualization. Graph Drawing and Network Visualization are motivated by applications where it is crucial to visually analyze and interact with relational datasets. Examples of such application areas include social sciences, Internet and Web computing, information systems, computational biology, networking, VLSI circuit design, and software engineering. This year the Steering Committee of GD decided to extend the name of the conference from the'International Symposium on Graph Drawing'to the'International Symposium on Graph Drawing and Network Visualization'in order to better emphasize the dual focus of the conference on combinatorial and algorithmic aspects as well as the design of network visualization systems and interfaces.

This book constitutes the thoroughly refereed workshop post-proceedings of the 15th International Workshop on Approximation and Online Algorithms, WAOA 2017, held in Vienna, Austria, in September 2017 as part of ALGO 2017.The 23 revised full papers presented in this book were carefully reviewed and selected from 50 submissions. Topics of interest for WAOA 2017 were: graph algorithms; inapproximability results; network design; packing and covering; paradigms for the design and analysis of approximation and online algorithms; parameterized complexity; scheduling problems; algorithmic game theory; coloring and partitioning; competitive analysis; computational advertising; computational finance; cuts and connectivity; geometric problems; mechanism design; resource augmentation; and real-world applications.

This book constitutes the proceedings of the 22nd International Symposium on Graph Drawing, GD 2014, held in Würzburg, Germany, in September 2014. The 41 full papers presented in this volume were carefully reviewed and selected from 72 submissions. The back matter of the book also contains 2 page poster papers presented at the conference. The contributions are organized in topical sections named: planar subgraphs; simultaneous embeddings; applications; contact representations; k-planar graphs; crossing minimization; level drawings; theory; fixed edge directions; drawing under constraints; clustered planarity; and greedy graphs.

This book constitutes the thoroughly refereed post-conference proceedings of the 16th Japanese Conference on Discrete and computational Geometry and Graphs, JDCDGG 2013, held in Tokyo, Japan, in September 2013.The total of 16 papers included in this volume was carefully reviewed and selected from 58 submissions. The papers feature advances made in the field of computational geometry and focus on emerging technologies, new methodology and applications, graph theory and dynamics.

This book constitutes the refereed contest reports of the 1st International Workshop, VAAM 2014, held in Stockholm, Sweden, in August 2014. The 10 revised full papers presented were carefully reviewed and selected from 13 submissions. The aim of this workshop is to provide an overview of state of the art methods for audience measurements in retail and Digital Signage, end-users attraction, and stimulate the creation of appropriate benchmark dataset to be used as reference for the development of novel audience measurement algorithms. Papers are invited under the following topics: demographics and modeling consumer behaviour.

This book constitutes the refereed proceedings of the First International Workshop on Bayesian and grAphical Models for Biomedical Imaging, BAMBI 2014, held in Cambridge, MA, USA, in September 2014 as a satellite event of the 17th International Conference on Medical Image Computing and Computer Assisted Intervention, MICCAI 2014.The 11 revised full papers presented were carefully reviewed and selected from numerous submissions with a key aspect on probabilistic modeling applied to medical image analysis. The objectives of this workshop compared to other workshops, e.g. machine learning in medical imaging, have a stronger mathematical focus on the foundations of probabilistic modeling and inference. The papers highlight the potential of using Bayesian or random field graphical models for advancing scientific research in biomedical image analysis or for the advancement of modeling and analysis of medical imaging data.

This book constitutes the thoroughly refereed post-conference proceedings of the 10th International Workshop on Graphics Recognition, GREC 2013, held in Bethlehem, PA, USA, in August 2013.The 20 revised full papers presented were carefully reviewed and selected from 32 initial submissions. Graphics recognition is a subfield of document image analysis that deals with graphical entities in engineering drawings, sketches, maps, architectural plans, musical scores, mathematical notation, tables, and diagrams. Accordingly the conference papers are organized in 5 topical sessions on symbol spotting and retrieval, graphics recognition in context, structural and perceptual based approaches, low level processing, and performance evaluation and ground truthing.

This book constitutes the revised selected papers of the 8th International Workshop on Algorithms and Computation, WALCOM 2014, held in Chennai, India, in February 2014. The 29 full papers presented together with 3 invited talks were carefully reviewed and selected from 62 submissions. The papers are organized in topical sections on computational geometry, algorithms and approximations, distributed computing and networks, graph algorithms, complexity and bounds, and graph embeddings and drawings.

This book constitutes the refereed proceedings of the 4th International Workshop and Challenge on Computational Methods and Clinical Applications for Spine Imaging, CSI 2016, held in conjunction with MICCAI 2016, in Athens, Greece, in October 2016. The 13 workshop papers were carefully reviewed and selected for inclusion in this volume. They aim at reviewing the state-of-the-art techniques, sharing the novel and emerging analysis and visualization techniques and discussing the clinical challenges and open problems in this rapidly growing field - including all major aspects of problems related to spine imaging, including clinical applications of spine imaging, computer aided diagnosis of spine conditions, computer aided detection of spine-related diseases, emerging computational imaging techniques for spinal diseases, fast 3D reconstruction of spine, feature extraction, multiscale analysis, pattern recognition, image enhancement of spine imaging, image-guided spine intervention and treatment, multimodal image registration and fusion for spine imaging, novel visualization techniques, segmentation techniques for spine imaging, statistical and geometric modeling for spine and vertebra, spine and vertebra localization.

This book constitutes the thoroughly refereed post-conference proceedings of the 11th International Workshop on Graphics Recognition, GREC 2015, held in Nancy, France, in August 2015. The 10 revised full papers presented were carefully reviewed and selected from 19 initial submissions. They contain both classical and emerging topics of Graphics Recognition, namely symbol spotting; recognition in context; perceptual based approaches and grouping; low level processing; off-line to on-line and interactive systems; structure based approaches; performance evaluation and ground truthing; content based retrieval.

This book contains the thoroughly refereed post-conference proceedings of the 14th Information Hiding Conference, IH 2012, held in Berkeley, CA, USA, in May 2012. The 18 revised full papers presented were carefully reviewed and selected from numerous submissions. The papers are organized in topical sections on multimedia forensics and counter-forensics, steganalysis, data hiding in unusual content, steganography, covert channels, anonymity and privacy, watermarking, and fingerprinting.

This book constitutes the refereed proceedings of the International Conference, VISIGRAPP 2011, the Joint Conference on Computer Vision, Theory and Applications (VISAPP), on Imaging Theory and Applications (IMAGAPP), on Computer Graphics Theory and Applications (GRAPP), and on Information Visualization Theory and Applications (IVAPP), held in Vilamoura, Portugal, in March 2011. The 15 revised full papers presented together with one invited paper were carefully reviewed and selected. The papers are organized in topical sections on computer graphics theory and applications; imaging theory and applications; information visualization theory and applications; and computer vision theory and applications.

This book constitutes the thoroughly refereed post-conference proceedings of the 21st International Symposium on Graph Drawing, GD 2013, held in Bordeaux, France, in September 2013. The 42 revised full papers presented together with 12 revised short papers, 3 invited talks and 1 poster description were carefully reviewed and selected from 110 submissions. The papers are organized in topical sections on upward drawings, planarity, beyond planarity, geometric representations, 3D et al., universality, practical graph drawing, subgraphs, crossings, geometric graphs and geographic networks, angular restrictions, grids, curves and routes. The book also contains a short description of the graph drawing contest.

This book constitutes the thoroughly refereed post-workshop proceedings of the International Workshop on Brain Lesion (BrainLes), Brain Tumor Segmentation (BRATS) and Ischemic Stroke Lesion Segmentation (ISLES), held in Munich, Germany, on October 5, 2015, in conjunction with the International Conference on Conference on Medical Image Computing and Computer-Assisted Intervention, MICCAI 2015. The 25 papers presented in this volume were carefully reviewed and selected from 28 submissions. They are grouped around the following topics: brain lesion image analysis; brain tumor image segmentation; ischemic stroke lesion image segmentation.

This book constitutes the thoroughly refereed post-conference proceedings of six international workshops held in the framework of the 7th Pacific-Rim Symposium on Image and Video Technology, PSIVT 2015, during November 23-24, 2015, in Auckland, New Zealand. The 29 revised full papers presented were carefully selected from 58 submissions. Their topics diversely ranged from well-established areas to novel current trends: robot vision, RV 2015; 2D and 3D geometric properties from incomplete data, GPID 2015; vision meets graphics, VG 2015; passive and active electro-optical sensors for aerial and space imaging, EO4AS 2015; mathematical and computational methods in biomedical imaging and image analysis, MCBMIIA 2015; and video surveillance, VSWS 2015.

This book constitutes the thoroughly refereed post-workshop proceedings of the First International Workshop on Patch-based Techniques in Medical Images, Patch-MI 2015, which was held in conjunction with MICCAI 2015, in Munich, Germany, in October 2015. The 25 full papers presented in this volume were carefully reviewed and selected from 35 submissions. The topics covered are such as image segmentation of anatomical structures or lesions; image enhancement; computer-aided prognostic and diagnostic; multi-modality fusion; mono and multi modal image synthesis; image retrieval; dynamic, functional physiologic and anatomic imaging; super-pixel/voxel in medical image analysis; sparse dictionary learning and sparse coding; analysis of 2D, 2D+t, 3D, 3D+t, 4D, and 4D+t data.

This book constitutes the refereed proceedings of the International Conference, VISIGRAPP 2010, the Joint Conference on Computer Vision Theory and Applications (VISAPP), on Imaging Theory and Applications (IMAGAPP), and on Computer Graphics Theory and Applications (GRAPP), held in Angers, France, in May 2010. The 19 revised full papers presented together with two invited papers were carefully reviewed and selected. The papers are organized in topical sections on computer vision theory and applications; imaging theory and applications; computer graphics theory and applications; and information visualization theory and applications.

The two volumes LNCS 6553 and 6554 constitute the refereed post-proceedings of 7 workshops held in conjunction with the 11th European Conference on Computer Vision, held in Heraklion, Crete, Greece in September 2010. The 62 revised papers presented together with 2 invited talks were carefully reviewed and selected from numerous submissions. The second volume contains 34 revised papers selected from the following workshops: Workshop on color and Reflectance in Imaging and Computer Vision (CRICV 2010); Workshop on Media Retargeting (MRW 2010); Workshop on Reconstruction and Modeling of Large-Scale 3D Virtual Environments (RMLE 2010); and Workshop on Computer Vision on GPUs (CVGPU 2010).

This book constitutes the thoroughly refereed post-conference proceedings of the Third International Conference on Scale Space Methods and Variational Methods in Computer Vision, SSVM 2011, held in Ein-Gedi, Israel in May/June 2011. The 24 revised full papers presented together with 44 poster papers were carefully reviewed and selected from 78 submissions. The papers are organized in topical sections on denoising and enhancement, segmentation, image representation and invariants, shape analysis, and optical flow.

This volume constitutes the thoroughly refereed post-conference proceedings of the 8th International Conference on Curves and Surfaces, held in Paris, France, in June 2014. The conference had the overall theme:'Representation and Approximation of Curves and Surfaces and Applications'. The 32 revised full papers presented were carefully reviewed and selected from 39 submissions. The scope of the conference was on following topics: approximation theory, computer-aided geometric design, computer graphics and visualization, computational geometry and topology, geometry processing, image and signal processing, interpolation and smoothing, mesh generation, finite elements and splines, scattered data processing and learning theory, sparse and high-dimensional approximation, subdivision, wavelets and multi-resolution method.

This book constitutes the thoroughly refereed post-conference proceedings of the Third International Workshop on Spatio-temporal Image Analysis for Longitudinal and Time-Series Image Data, STIA 2014, held in conjunction with MICCAI 2014 in Boston, MA, USA, in September 2014.The 7 papers presented in this volume were carefully reviewed and selected from 15 submissions. They are organized in topical sections named: longitudinal registration and shape modeling, longitudinal modeling, reconstruction from longitudinal data, and 4D image processing.

This book contains the thoroughly refereed post-conferernce proceedings of the 13th Information Hiding Conference, IH 2011, held in Prague, Czech Republic, in May 2011.Included in this volume are 23 carefully reviewed papers that were selected out of 69 submissions. The contributions are organized in topical sections on: fingerprinting, anonymity and privacy, steganography and steganalysis, watermarking, digital rights management and digital forensics, and digital hiding in unusual context. Also included are the papers that were presented as part of the special session dedicated to the BOSS (Break Our Steganographic System) contest.

This book constitutes the thoroughly refereed post-conference proceedings of the four workshops on Photographic Aesthetics and Non-Photorealistic Rendering (PAESNPR13), Geometric Properties from Incomplete Data (GPID), Quality Assessment and Control by Image and Video Analysis (QACIVA) and Geometric Computation for Computer Vision (GCCV2013), held in conjunction with the 6th Pacific-Rim Symposium on Image and Video Technology (PSIVT) in Guanajuato, Mexico during October 28-November 1, 2013. The 38 revised full papers presented were carefully selected from numerous submissions and cover all aspects of Imaging and Graphics Hardware and Visualization, Image/Video Coding and Transmission; Processing and Analysis; Retrieval and Scene Understanding, but also Applications of Image and Video Technology, Biomedical Image Processing and Analysis, Biometrics and Image Forensics, Computational Photography and Arts, Computer and Robot Vision, Pattern Recognition and Video Surveillance.

This book constitutes the refereed proceedings of the Thailand-Japan Joint Conference on Computational Geometry and Graphs, TJJCCGG 2012, held in Bangkok, Thailand, in December 2012.The 15 original research papers presented were selected from among six plenary talks, one special public talk and 41 talks by participants from about 20 countries around the world. TJJCCGG 2012 provided a forum for researchers working in computational geometry, graph theory/algorithms and their applications.

This book constitutes the thoroughly refereed post workshop proceedings of the 10th International Workshop on Approximation and Online Algorithms, WAOA 2012, held in Ljubljana, Slovenia, in September 2012 as part of the ALGO 2012 conference event. The 22 revised full papers presented together with invited talk were carefully reviewed and selected from 60 submissions. The workshop covered areas such as geometric problems, online algorithms, scheduling, algorithmic game theory, and approximation algorithms.

This comprehensive new Springer publication constitutes the thoroughly refereed post-conference proceedings of the 15th International Symposium on Graph Drawing, GD 2007, held in Sydney, Australia, in September of 2007. The 27 full papers and 9 short papers presented together with 2 invited talks, and a report on the symposium's graph drawing contest were carefully selected from 74 initial submissions. All of the current hot topics in graph drawing are addressed here.

With the swift development of video imaging technology and the drastic improvements in CPU speed and memory, both video processing and computational video are becoming more and more popular. Similar to the digital revolution in photography of fifteen years ago, today digital methods are revolutionizing the way television and movies are being made. With the advent of professional digital movie cameras, digital projector technology for movie theaters, and 3D movies, the movie andtelevision production pipeline is turning all-digital, opening upnumerous new opportunities for the way dynamic scenes are acquired, video footage can be edited, and visual media may be experienced.This state-of-the-art survey provides a compilation of selected articles resulting from a workshop on Video Processing and Computational Video, held at Dagstuhl Castle, Germany, in October 2010. The seminar brought together junior and seniorresearchers from computer vision, computer graphics, and image communication, both from academia and industry, to address the challenges in computational video. During this workshop, 43 researchers from all over the world discussed the state of the art, contemporary challenges, and future research in imaging,processing, analyzing, modeling, and rendering of real-world, dynamic scenes.The 8 thoroughly revised papers presented were carefully reviewed and selected from more than 30 lectures given at the seminar. The articles give a good overview of the field of computational video and video processing with a specialfocus on computational photography, video-based rendering, and 3D video.

This book constitutes the thoroughly refereed post workshop proceedings of the 8th International Workshop on Approximation and Online Algorithms, WAOA 2010, held in Liverpool, UK, in September 2010 as part of the ALGO 2010 conference event.The 23 revised full papers presented were carefully reviewed andselected from 58 submissions. The workshop covered areas such asalgorithmic game theory, approximation classes, coloring andpartitioning, competitive analysis, computational finance, cuts andconnectivity, geometric problems, inapproximability results, echanismdesign, network design, packing and covering, paradigms for design and analysis of approximation and online algorithms, parameterizedcomplexity, randomization techniques, real-world applications, andscheduling problems.

The four-volume set LNCS 6492-6495 constitutes the thoroughly refereed post-proceedings of the 10th Asian Conference on Computer Vision, ACCV 2009, held in Queenstown, New Zealand in November 2010. All together the four volumes present 206 revised papers selected from a total of 739 Submissions. All current issues in computer vision are addressed ranging from algorithms that attempt to automatically understand the content of images, optical methods coupled with computational techniques that enhance and improve images, and capturing and analyzing the world's geometry while preparing the higher level image and shape understanding. Novel gemometry techniques, statistical learning methods, and modern algebraic procedures are dealt with as well.

The four-volume set LNCS 6492-6495 constitutes the thoroughly refereed post-proceedings of the 10th Asian Conference on Computer Vision, ACCV 2009, held in Queenstown, New Zealand in November 2010. All together the four volumes present 206 revised papers selected from a total of 739 Submissions. All current issues in computer vision are addressed ranging from algorithms that attempt to automatically understand the content of images, optical methods coupled with computational techniques that enhance and improve images, and capturing and analyzing the world's geometry while preparing the higher level image and shape understanding. Novel geometry techniques, statistical learning methods, and modern algebraic procedures are dealt with as well.

The four-volume set LNCS 6492-6495 constitutes the thoroughly refereed post-proceedings of the 10th Asian Conference on Computer Vision, ACCV 2009, held in Queenstown, New Zealand in November 2010. All together the four volumes present 206 revised papers selected from a total of 739 Submissions. All current issues in computer vision are addressed ranging from algorithms that attempt to automatically understand the content of images, optical methods coupled with computational techniques that enhance and improve images, and capturing and analyzing the world's geometry while preparing the higher level image and shape understanding. Novel gemometry techniques, statistical learning methods, and modern algebraic procedures are dealt with as well.

This state-of-the-art survey features papers that were selected after an open call following the International Dagstuhl Seminar on Algorithmic Methods for Railway Optimization. The second part of the volume constitutes the refereed proceedings of the 4th International Workshop on Algorithmic Methods and Models for Optimization of Railways. The 17 full papers presented here were carefully reviewed and selected from numerous submissions.

This book constitutes the thoroughly refereed post-proceedings of the 14th International Symposium on Graph Drawing, GD 2006, held in Karlsruhe, Germany. The 33 revised full papers and 5 revised short papers presented together with 2 invited talks, 1 system demo, 2 poster papers address all current aspects in graph drawing, ranging from foundational and methodological issues to applications for various classes of graphs in a variety of fields.

This Festschrift volume, published in honour of J. Ian Munro, contains contributions written by some of his colleagues, former students, and friends. In celebration of his 66th birthday the colloquium'Conference on Space Efficient Data Structures, Streams and Algorithms'was held in Waterloo, ON, Canada, during August 15-16, 2013. The articles presented herein cover some of the main topics of Ian's research interests. Together they give a good overall perspective of the last 40 years of research in algorithms and data structures.

The Fifth Workshop on Approximation and Online Algorithms (WAOA 2007) focused on the design and analysis of algorithms for online and computationally hard problems. Both kinds of problems have a large number of applications from a variety of?elds. WAOA 2007 took place in Eilat, Israel, during October 11–12, 2007. The workshop was part of the ALGO 2007 event that also hosted ESA 2007, and PEGG 2007. The previous WAOA workshops were held in Budapest (2003), Rome (2004), Palma de Mallorca (2005) and Zurich (2006). The proceedings of these previous WAOA workshops have appeared as LNCS volumes 2909, 3351, 3879 and 4368, respectively. Topics of interest for WAOA 2007 were: algorithmic game theory, appro- mation classes, coloring and partitioning, competitive analysis, computational?nance, cuts and connectivity, geometric problems, inapproximability results, mechanism design, network design, packing and covering, paradigms for design and analysis of approximation and online algorithms, randomization techniques, real-world applications, and scheduling problems. In response to the call for - pers, we received 56 submissions. Each submission was reviewed by at least three referees, and the vast majority by at least four referees. The submissions were mainly judged on originality, technical quality, and relevance to the topics of the conference. Based on the reviews, the Program Committee selected 22 papers. We are grateful to Andrei Voronkov for providing the EasyChair conference system which was used to manage the electronic submissions, the review process, and the electronic PC meeting. It made our task much easier.

This book constitutes the thoroughly refereed post-proceedings of the 4th International Workshop on Approximation and Online Algorithms, WAOA 2006, held in Zurich, Switzerland in September 2006 as part of the ALGO 2006 conference event. The 26 revised full papers presented were carefully reviewed and selected from 62 submissions.

The pixelization paradigm states as a postulate that pixelization methods are rich and are worth exploring as far as possible. In fact, we think that the strength of these methods lies in their simplicity, in their high-density way of information representation property and in their compatibility with neurocognitive processes. • Simplicity, because pixelization belongs to two-dimensional information visualization methods and its main idea is identifying a “pixel” with an informational entity in order to translate a set of informational entities into an image. • High-density way of information representation property, firstly because pixelization representation contains a third dimension—each pixel's color—and secondly because pixelization is a “compact” (two-dimensional) way of representing information compared with linear one-dimensional representations (Ganascia, p.255). • Compatibility with neurocognitive processes, firstly because we are thr- dimensional beings and thus we are intrinsically better at grasping one- or two-dimensional data, and secondly because the cerebral cortex is typically a bi-dimensional structure where metaphorically the neurons can be assimilated to “pixels,” whose activity plays the role of color (Lévy, p.3). The pixelization paradigm may be studied along two related directions: pixelization and its implementation and pixelization and cognition. The first direction—pixelization and its implementation—may be divided into two parts: pixelization theory and pixelization application.

The 32nd International Workshop on Graph-Theoretic Concepts in Computer Science (WG 2006) was held on the island of Sotra close to the city of Bergen on the west coast of Norway. The workshop was organized by the Algorithms Research Group at the Department of Informatics, University of Bergen, and it took place from June 22 to June 24. The 78 participants of WG 2006 came from the universities and research institutes of 17 di?erent countries. The WG 2006 workshop continues the series of 31 previous WG workshops. Since 1975,WG has taken place 20 times in Germany, four times in The Neth- lands, twice in Austria as well as oncein France,in Italy, in Slovakia,in Switz- land and in the Czech Republic, and has now been held for the?rst time in Norway. The workshop aims at uniting theory and practice by demonstrating how graph-theoretic concepts can be applied to various areas in computer s- ence, or by extracting new problems from applications. The goal is to present recent research results and to identify and explore directions of future research. The talks showed how recent researchresults from algorithmic graph theory can be used in computer science and which graph-theoreticquestions arisefrom new developments in computer science. There were two fascinating invited lectures by Hans Bodlaender (Utrecht, The Netherlands) and Tandy Warnow (Austin, USA).