Ari Rappoport's homepage

Prof. Ari Rappoport

My two main areas of interest are (1) Computational Linguistics / Natural Language Processing and (2) Geometric and Solid Modeling. In addition, I have done work in Computer Graphics, Video and Image Processing, and Object-Oriented Design.

Language Research // Geometry Research // Publications (Language) // Publications (Geometry) // Addresses Etc // Students // Teaching // Business

Language Research

My current research area is Computational Linguistics and Natural Language Processing (NLP). I am interested in a wide range of topics, including lexical semantics, parsing, computational modeling of language acquisition, and applications (e.g., mining web social media and technology for helping people read in foreign languages). In all of these, I focus on using fully unsupervised and semi-supervised methods, in order to make use of the huge corpora available today and to overcome the problems associated with supervised learning (annotation cost and the arbitrariness of annotation schemes).

Recent publications include 3 papers in EMNLP 2009, 4 papers in CoNLL 2009 (best paper award), 4 papers in ACL 2008, a paper in each of ACL 2009 and EACL 2009, 2 papers in COLING 2008, and 3 papers in ACL 2007. I was a program committee member in EMNLP 2009, CoNLL 2009, EACL 2009, EACL Cognitive 2009, COLING 2008, CoNLL 2008 and the ACL 2007 Workshop on Cognitive Aspects of Computational Language Acquisition. I was the program chair for the 2007 Israel Seminar on Computational Linguistics (ISCOL '07).

Publications (Language)

NLP publications include 3 papers in EMNLP 2009, 4 papers in CoNLL 2009 (best paper award), 1 in ACL 2009, 1 in EACL 2009, 4 in ACL 2008, 3 in ACL 2007, 1 in ICWSM 2009, 2 in COLING 2008, 1 in ACL 2006, and 4 in ACL and EACL workshops (2009, 2007, 2006, 2005).

[NEW] Dmitry Davidov, Ari Rappoport. Geo-mining: Discovery of Road and Transport Networks Using Directional Patterns. EMNLP 2009.
[NEW] Dmitry Davidov, Ari Rappoport. Enhancement of Lexical Concepts Using Cross-lingual Web Mining. EMNLP 2009.
[NEW] Ram Boukobza, Ari Rappoport. Multi-Word Expression Identification Using Sentence Surface Features. EMNLP 2009.
[NEW] Omri Abend, Roi Reichart, Ari Rappoport. Unsupervised Argument Identification for Semantic Role Labeling. ACL 2009 (long paper).
[NEW] Roi Reichart, Ari Rappoport. The NVI Clustering Evaluation Measure. Computational Natural Language Learning (CoNLL) 2009.
[NEW] (BEST PAPER AWARD) Roi Reichart, Ari Rappoport. Sample Selection for Statistical Parsers: Cognitively Driven Algorithms and Evaluation Measures. Computational Natural Language Learning (CoNLL) 2009.
[NEW] Roi Reichart, Ari Rappoport. Automatic Selection of High Quality Parses Created By a Fully Unsupervised Parser. Computational Natural Language Learning (CoNLL) 2009.
[NEW] Dmitry Davidov, Roi Reichart, Ari Rappoport. Superior and Efficient Fully Unsupervised Pattern-based Concept Acquisition Using an Unsupervised Parser. Computational Natural Language Learning (CoNLL) 2009.
[NEW] Oren Tsur, Ari Rappoport. RevRank: a Fully Unsupervised Algorithm for Selecting the Most Helpful Book Reviews. Third International AAAI Conference on Weblogs and Social Media (ICWSM 2009) (long paper).
[NEW] Dmitry Davidov, Ari Rappoport. Translation and Extension of Concepts Across Languages. EACL 2009 (long paper).
[NEW] Elad Dinur, Dmitry Davidov, Ari Rappoport. Unsupervised Concept Discovery In Hebrew Using Simple Unsupervised Word Prefix Segmentation for Hebrew and Arabic. EACL 2009 Workshop on Computational Approaches to Semitic Languages.
Dmitry Davidov, Ari Rappoport. Unsupervised Discovery of Generic Relationships Using Pattern Clusters and its Evaluation by Automatically Generated SAT Analogy Questions. ACL 2008 (long paper).
Dmitry Davidov, Ari Rappoport. Classification of Semantic Relationships between Nominals Using Pattern Clusters. ACL 2008 (long paper).
Vivek Srikumar, Roi Reichart, Mark Sammons, Ari Rappoport, Dan Roth. Extraction of Entailed Semantic Relations Through Syntax-based Comma Resolution. ACL 2008 (long paper).
Roi Reichart, Katrin Tomanek, Udo Hahn, Ari Rappoport. Multi-Task Active Learning for Linguistic Annotations. ACL 2008 (long paper).
Omri Abend, Roi Reichart, Ari Rappoport. A Supervised Algorithm for Verb Disambiguation into VerbNet Classes. COLING 2008 (long paper).
Roi Reichart, Ari Rappoport. Unsupervised Induction of Labeled Parse Trees by Clustering with Syntactic Features. COLING 2008 (long paper).
Dmitry Davidov, Ari Rappoport, Moshe Koppel. Fully Unsupervised Discovery of Concept-Specific Relationships by Web Mining. Proceedings, ACL 2007 (long paper).
Roi Reichart, Ari Rappoport. An Ensemble Method for Selection of High Quality Parses. ACL 2007 (long paper).
Roi Reichart, Ari Rappoport. Self-Training for Enhancement and Domain Adaptation of Statistical Parsers Trained on Small Datasets. ACL 2007 (long paper).
Oren Tsur, Ari Rappoport. Using Classifier Features for Studying the Effect of Native Language on the Choice of Written Second Language Words. Proceedings, ACL 2007 Workshop on Cognitive Aspects of Computational Language Acquisition, June 2007, Prague.
Dmitry Davidov, Ari Rappoport. Efficient Unsupervised Discovery of Word Categories Using Symmetric Patterns and High Frequency Words. COLING-ACL 2006 (long paper).
Ari Rappoport, Tsahi Levent-Levi. Induction of Cross-Language Affix and Letter Sequence Correspondence. Proceedings, EACL 2006 Workshop on Cross-Language Knowledge Induction, April 2006, Trento, Italy.
Ari Rappoport, Vera Sheinman. A Second Language Acquisition Model Using Example Generalization and Concept Categories. Proceedings, ACL 2005 Workshop on Psycho-computational Models of Human Language Acquisition, June 2005, Ann Arbor.

Geometry Research

Research: The theme that ties most of my research in geometric modeling and computer graphics is the notion of "families of geometric objects" (see UPR and feature-based data exchange project page, and GGC, shape animation, parametric fonts, 2-D+surface+volume preservation constraints, real-time Booleans, below). A second theme is the study of fundamental geometric structures (see medial axis, Voronoi graph, ECDT, compatible decompositions). In addition, I enjoy doing research on various cool graphics subjects (see real-time reflections, textures from image sequences, 3-D effects on still images, image-based rendering).

Community: In 1992 I started the Geometric Modeling and Computer Graphics Lab at HUJI, after a postdoc at the IBM TJ Watson Research Center in New York. I was an associate editor of ACM Transactions on Graphics, and a paper committee member for Solid Modeling '95, Eurographics '96, CSG '96, Theory and Practice of Geometric Modeling (Blaubeuren II) 1996, Solid Modeling '97, TeamCAD '97, Eurographics '97, Computer Graphics International '98, CSG '98, Eurographics '98, the 1999 ACM/Siggraph Symposium on Interactive 3D Graphics, Solid Modeling '99, Eurographics '99, Computer Graphics International '99, International Conference on Visual Computing ICVC '99, Pacific Graphics '99, Geometric Modeling and Processing 2000, Solid Modeling '04, Solid and Physical Modeling '05, Shape Modeling International '05, Solid and Physical Modeling '06, Shape Modeling International '06, Solid and Physical Modeling '07, Shape Modeling International '07, International Conference on Computer Graphics Theory and Applications (GRAPP) '07, Solid and Physical Modeling '08, Shape Modeling International '08, Computer Graphics International (CGI) '08, Product Life-Cycle (PLM) '08, International Conference on Computer Graphics Theory and Applications (GRAPP) '08, Solid and Physical Modeling '09, and Shape Modeling International '09.

Publications (Geometry)

Following is a partial list of publications, arranged according to topic. Clicking on a paper's title leads to its abstract. Some papers contain links to pdf versions of the full paper. To obtain other full papers please email me personally.

The Universal Product Representation // Voronoi Graph (Medial Axis) // Interactive Rendering // Generative and Declarative Modeling // Polygons and Polyhedra // Digital Typography // Curves, Surfaces and Volumes // Morphing and Deformations // Images and Video // User Interface //

The Universal Product Representation

Rappoport Ari, Spitz Steven, Etzion Michal. One-dimensional selections for feature-based data exchange. Proceedings, Solid Modeling '05, June 2005, MIT. (pdf)
Rappoport Ari, Spitz Steven, Etzion Michal. Two-dimensional selections for feature-based data exchange. Proceedings, Geometric Modeling and Processing (GMP) 2006, July 2006, Pittsburgh, USA. (pdf)
Spitz Steven, Rappoport Ari. Integrated feature-based and geometric CAD data exchange. Proceedings, Solid Modeling '04, June 2004, Genova, Italy, ACM Press. (pdf)
Rappoport Ari. An architecture for universal CAD data exchange. Proceedings, Solid Modeling '03, June 2003, Seattle, Washington, ACM Press. (pdf)

The Voronoi Graph (Medial Axis)

Etzion Michal, Rappoport Ari. Computing Voronoi skeletons of a 3-D polyhedron by space subdivision. Computational Geometry: Theory and Applications, 21(3):87-120, March 2002. (pdf)
Sheffer Alla, Etzion Michal, Rappoport Ari, Bercovier Michel. Hexahedral mesh generation using the embedded Voronoi graph. Proceedings, Seventh International Meshing Roundtable, pp. 347-364, 1998. (pdf)
Etzion Michal, Rappoport Ari. Computing the Voronoi diagram of a 3-D polyhedron by separate computation of its symbolic and geometric parts. Proceedings, Fifth ACM/Siggraph Symposium on Solid Modeling and Applications (Solid Modeling '99), ACM Press, 1999.
Etzion Michal, Rappoport Ari. A boundary sampling algorithm for computing the Voronoi graph of a 2-D polygon. Technical Report, Institute of Computer Science, The Hebrew University, 1996.

Interactive Rendering

Ofek Eyal, Rappoport Ari. Interactive reflections on curved objects. Proceedings of Siggraph 98. In Computer Graphics Proceedings, Annual Conference Series, 1998, ACM SIGGRAPH, pp. 333-342.
Rappoport Ari, Spitz Steven. Interactive Boolean operations for conceptual design of 3-D solids. Proceedings of Siggraph 97. In Computer Graphics Proceedings, Annual Conference Series, 1997, ACM SIGGRAPH, pp. 269-278. (pdf)

Generative and Declarative Modeling

Rappoport Ari. The Generic Geometric Complex (GGC): a modeling scheme for families of decomposed pointsets. Proceedings, Fourth ACM/Siggraph Symposium on Solid Modeling and Applications (Solid Modeling '97), May 1997, Atlanta, ACM Press, pp. 19-30. (pdf)
Rappoport Ari. Breps as displayable-selectable models in interactive design of families of geometric objects. Geometric Modeling: Theory and Practice, Strasser, Klein, Rau, (Eds), Springer-Verlag, 1997, pp. 206-225 (proceedings, Theory and Practice of Geometric Modeling (Blaubeuren II), Tübingen, Germany, October 1996.) (pdf)
Rappoport Ari. Parametric and declarative modeling of families of geometric objects. Presented at the IFIP Workshop on Geometric Modeling in CAD, Airlie, VA, May 1996. Abstract only.
Rappoport Ari. Geometric modeling: a new fundamental framework and its practical implications. Proceedings, Third ACM/Siggraph Symposium on Solid Modeling and Applications (Solid Modeling '95), May 1995, Salt Lake City, ACM Press, pp. 31-42.
Hel-Or Yaacov, Rappoport Ari, Werman Michael. Relaxed parametric design with probabilistic constraints. Computer-Aided Design, 26(6):426-434, 1994. Also: proceedings, Second ACM/Siggraph Symposium on Solid Modeling and Applications, May 1993, Montreal, ACM Press, pp. 261-270. (pdf)
Emmerik, M.J.G. Maarten (van), Rappoport Ari, Rossignac Jarek. Simplifying interactive design of solid models: a hypertext approach. The Visual Computer: an International Journal of Computer Graphics, 9:239-254, 1993.
Rappoport Ari. A scheme for single instance representation in hierarchical assembly graphs. Falcidieno, B., Kunii T.L. (eds), Geometric Modeling in Computer Graphics, pp. 213-224, Springer, 1993 (IFIP Conference on Geometric Modeling in Computer Graphics, Genova, Italy, June 1993) (An updated version is available). (pdf of the updated version.)

Representations and Algorithms for Polygons and Polyhedra

Etzion Michal, Rappoport Ari. On compatible star decompositions of simple polygons. IEEE Transactions on Visualization and Computer Graphics, 3(1):87-95, 1997.
Rappoport Ari. The extended convex differences tree (ECDT) representation for n-dimensional polyhedra. Intl. Journal of Computational Geometry and Applications, 1(3):227-241, 1991. Also: proceedings, First ACM/Siggraph Symposium on Solid Modeling Foundations and CAD/CAM Applications, June 1991, Austin, ACM Press, pp. 139-148.
Rappoport Ari. An efficient adaptive algorithm for constructing the convex differences tree of a simple polygon. Computer Graphics Forum, 11(4):235-240, 1992.
Rappoport Ari. An efficient algorithm for line and polygon clipping. The Visual Computer: an International Journal of Computer Graphics, 7(1):19-28, 1991.
Rappoport Ari. Using convex differences for hierarchical representations of polygonal maps. Graphics Interface 90, Halifax, Canada, May 1990, pp. 183-189.

Digital Typography

Shamir Ariel, Rappoport Ari. Compacting Oriental Fonts by Optimizing Parametric Elements. The Visual Computer, 15(6):302-318, 1999.
Shamir Ariel, Rappoport Ari. Dynamic typography. Technical Report, Institute of Computer Science, The Hebrew University, 1997.
Shamir Ariel, Rappoport Ari. Feature-based design of fonts using constraints. Electronic Publishing, Artistic Imaging and Digital Typography, Proc. of the EP'98 and RIDT'98 Conferences, St Malo, March 30 - April 3, 1998. Eds. Roger D. Hersch, Jacques Andre, Heather Brown, LNCS, Springer Verlag, 1998. Presented at Raster Imaging and Digital Typography 1998 (RIDT '98), April 1998.
Shamir Ariel, Rappoport Ari. Extraction of typographic elements from outline representations of fonts. Computer Graphics Forum, 15(3):259-268, 1996 (proceedings, Eurographics '96). (pdf)
Shamir Ariel, Rappoport Ari. Quality enhancements of digital outline fonts. Computers and Graphics, Special Issue on Graphics in Electronic Printing and Publishing, 21(6):713-725, 1997.

Curves, Surfaces and Volumes

Rappoport Ari, Sheffer Alla, Bercovier Michel. Volume-preserving free-form solids. IEEE Transactions on Visualization and Computer Graphics, 2(1):19-27, 1996. Also: proceedings, Third ACM/Siggraph Symposium on Solid Modeling and Applications (Solid Modeling '95), May 1995, Salt Lake City, ACM Press, pp. 361-372.
Rappoport Ari, Hel-Or Yaacov, Werman Michael. Interactive design of smooth objects using probabilistic point constraints. ACM Transactions on Graphics, 13(2):156-176, 1994.
Rappoport Ari. Rendering curves and surfaces with hybrid subdivision and forward differencing. ACM Transactions on Graphics, 10(4):323-341, October 1991.

Morphing and Deformations

Shapira Michal, Rappoport Ari. Shape blending using the star-skeleton representation. IEEE Computer Graphics and Applications, 15(2):44-50, March 1995. (pdf)
Borrel Paul, Rappoport Ari. Simple constrained deformations for geometric modeling and interactive design. ACM Transactions on Graphics, 13(2):137-155, 1994. (pdf)

Modeling and Rendering from Images and Image Sequences

Lischinski Dani, Rappoport Ari. Image-based rendering for non-diffuse synthetic scenes. Proceedings, Ninth Eurographics Workshop on Rendering, 1998, pp. 301-314. (pdf)
Zakai Yaron, Rappoport Ari. Three-dimensional modeling and effects on still images. Computer Graphics Forum, 15(3):3-10, 1996 (proceedings, Eurographics '96).
Ofek Eyal, Shilat Erez, Rappoport Ari, Werman Michael. Multiresolution textures from image sequences. IEEE Computer Graphics and Applications, 17(2):18-29, March 1997. Also Technical Report, Institute of Computer Science, The Hebrew University, 1994.

User Interface

Rappoport Ari. Direct manipulation devices for the design of geometric constraint networks. Magnenat-Thalmann, N., Thalmann, D. (eds), Communicating with Virtual Worlds, pp. 294-305, Springer, 1993 (proceedings, Computer Graphics International '93, Lausanne, June 1993.)
Rappoport Ari, Emmerik M.J.G. Maarten (van). User interface devices for rapid and exact number specification. ACM Transactions on Graphics, 12(4):348-354, 1993.

Addresses Etc

School of Computer Science and Engineering, The Hebrew University of Jerusalem, Jerusalem 91904, Israel. arir, AT symbol, cs huji ac il Office 23, Ross Building, Givat Ram Campus. Fax: +972-2-658-5439.

Students

Graduate (PhD, MSc) and Amirim

Omri Abend (P)
Noa Danon (P)
Dmitry Davidov (P)
Yakov Persky (P)
Roi Reichart (P)
Oren Tsur (P)
Shira Abram (M)
Ran Arad (M)
Ram Boukobza (M)
Eran Bringer (M)
Doron Shamia (M)
Daphna Shezaf (M)
Shulamit Umansky-Pesin (M)
Inna Zusman (M)

Alumni

Eyal Ofek (2001, PhD)
Arik Shamir (2000, PhD)
Michal Etzion (1999, PhD)
Elad Dinur (2009, MSc)
Ephi Sachs (with main supervisor Ido Dagan, 2008, MSc)
Shlomit Tshuva (2007, MSc)
Tsahi Levent-Levi (2006, MSc)
Shachar Mirkin (with main supervisor Ido Dagan, 2006, MSc)
Gil Asherie (2006, MSc)
Vera Sheinman (2005, MSc)
Elisheva Werner-Reiss (2000, MSc)
Daniel Goldschmidt (1999, MSc)
Yoav Samet (1996, MSc)
Yaron Zakai (1996, MSc)
Gidi Etzion (1996, MSc)
Alla Sheffer (with Michel Bercovier, 1995, MSc)
Michal Shapira (1994, MSc)
Evgeny Drapkin (1993, MSc)
Roy Schwartz (2008, Amirim)
Omri Abend (2006, Amirim)
Uri Cohen (2005, Amirim)
Steven Spitz (1995, Amirim)

Teaching

Computational Aspects of Applied Linguistics (CAAL class) // Seminar on Computational Applied Linguistics (CAL seminar) // Development of Commercial Software Workshop (Sadna) // Guided Projects, Lab Projects, etc

Business

My current focus is on novel methods for text reading and online language learning. I have been involved in various roles with high-tech companies and venture capital funds since 1994, in areas including textual search and ranking, online advertising, algorithmic trading, computer-aided design, computer graphics and image processing.