Research interests
My main interest has always been in languages for querying data: their design, computational complexity and optimisation. My PhD was about Queries on Graphs, a topic which has seen renewed interest with the advent of the semantic web and social networks. Other areas I have worked in include XML querying, active rule languages (similar to database triggers), deductive rule languages (e.g. Datalog), and compression techniques for XML. Most recently, I have been working on algorithms for combining recommendations from recommender systems as well as a query and transformation language for social network data.
Research projects
Two long-running projects are in the areas of
More recently, I have started working on
Research students
- Mirko Michele Dimartino (co-supervised with Andrea Calì and Alex Poulovassilis), working on integration and querying of linked data, completed his PhD in 2020
- Riccardo Frosini (co-supervised with Andrea Calì and Alex Poulovassilis), working on flexible querying, completed his PhD in 2017
- Petra Selmer (co-supervised with Alex Poulovassilis), working on flexible querying, completed her PhD in 2017
- Khaled Alyoubi (co-supervised with Sven Helmer), working on query optimisation, completed his PhD in 2016
- Mohammad Jaber (co-supervised with Panos Papapetrou and Sven Helmer), working on interaction networks, completed his PhD in 2015
- Manizheh Montazerian, working on optimising XML queries, completed her PhD in 2014
Recent talks
Slides, video and blog entry from inaugural lecture on 6 June 2016.
Automata and Formal Languages slides from a talk on research methods given to graduate students.
The following slides are from talks at recent conferences:
- Query Languages for Graph Databases - invited tutorial at AMW'09 (May 2009)
- XPath Query Satisfiability is in PTIME for Real-World DTDs - XSym'07 (September 2007)
- A Relaxed Approach to RDF Querying - ISWC'06 (November 2006)
- Containment for XPath Fragments under DTD Constraints - ICDT'03 (January 2003)
Recent publications
See also the list of publications from the DBLP Bibliography Server.
- R. Frosini, A. Poulovassilis, P.T. Wood and A. Calì, Optimisation Techniques for Flexible SPARQL Queries. ACM Trans. Web 16(4): 16:1-16:44 (2022)
- G.H.L. Fletcher, A. Poulovassilis, P. Selmer, P.T. Wood: Approximate Querying for the Property Graph Language Cypher. IEEE BigData 2019: 617-622
- M.M. Dimartino, A. Calì, A. Poulovassilis, P.T. Wood: Efficient Ontological Query Answering by Rewriting into Graph Queries. FQAS 2019: 75-84
- C. Gutierrez, J. Hidders, P.T. Wood: Graph Data Models. Encyclopedia of Big Data Technologies 2019
- R. Frosini, A. Calì, A. Poulovassilis and P.T. Wood, ``Flexible Query Processing for SPARQL,'' Semantic Web - Interoperability, Usability, Applicability, Vol. 8, No. 4, 2017, pp. 533-563.
- M. Jaber, P.T. Wood, P. Papapetrou and A. González-Marcos, ``A Multi-granularity Pattern-based Sequence Classification Framework for Educational Data,'' in Proc. 3rd IEEE Int. Conf. on Data Science and Advanced Analytics (DSAA) (Oct. 17-19, Montreal, Canada), 2016, pp. 370-378.
- A. Poulovassilis, P. Selmer and P.T. Wood, ``Approximation and Relaxation of Semantic Web Path Queries,'' Journal of Web Semantics, Vol. 40, October 2016, pp. 1-21.
- M.M. Dimartino, A. Calì, A. Poulovassilis, P.T. Wood, ``Query Rewriting under Linear EL Knowledge Bases,'' in 10th Int. Conf. on Web Reasoning and Rule Systems (RR) (September 9-11, Aberdeen, UK), 2016, pp. 61-76.
- K.H. Alyoubi, S. Helmer and P.T. Wood, ``Ordering Selection Operators Under Partial Ignorance,'' in Proc. 24th ACM Int. on Conf. on Information and Knowledge Management (CIKM) (Oct. 19-23, Melbourne, VIC, Australia,), 2015, pp. 1521-1530.
- M. Xie, L.V.S. Lakshmanan and P.T. Wood, ``Generating Top-k Packages via Preference Elicitation,'' in Proc. 41st Int. Conf. on Very Large Data Bases (VLDB) (August 31-September 4, Hawaii, USA), 2015, and PVLDB, Vol. 7, No. 14, 2014, pp. 1941-1952.
- M.M. Dimartino, A. Calì, A. Poulovassilis, P.T. Wood, ``Implementing Peer-to-Peer Semantic Integration of Linked Data,'' in 30th British Int. Conf. on Databases (BICOD) (July 6-8, Edinburgh, UK), 2015, pp. 41-45.
- M. Jaber, P. Papapetrou, A. González-Marcos and P.T. Wood, ``Analysing Online Education-based Asynchronous Communication Tools to Detect Students' Roles,'' in Proc. 7th Int. Conf. on Computer Supported Education (CSEDU) (May 23-25, Lisbon, Portugal), 2015, pp. 416-424.
- M.M. Dimartino, A. Calì, A. Poulovassilis, P.T. Wood, ``Peer-to-Peer Semantic Integration of Linked Data,'' in Fifth Int. Workshop on Linked Web Data Management (LWDM) (March 27, Brussels, Belgium), 2015, pp. 213-220.
- P. Selmer, A. Poulovassilis and P.T. Wood, ``Implementing Flexible Operators for Regular Path Queries,'' in Fourth Int. Workshop on Querying Graph Structured Data (GraphQ) (March 27, Brussels, Belgium), 2015, pp. 149-156.
- A. Calì, R. Frosini, A. Poulovassilis, P.T. Wood, ``Flexible Querying for SPARQL,'' in Proc. 13th Int. Conf. on Ontologies, DataBases, and Applications of Semantics (ODBASE) (October 27-31, Amantea, Italy), 2014, pp. 473-490.
- M. Jaber, P. Papapetrou, S. Helmer and P.T. Wood, ``Using Time-Sensitive Rooted PageRank to Detect Hierarchical Social Relationships,'' to appear in Proc. 13th Int. Symp. on Intelligent Data Analysis (IDA) (October 30-November 1, Leuven, Belgium), LNCS 8819, 2014, pp. 143-154.
- M. Jaber, P.T. Wood, P. Papapetrou and S. Helmer, ``Inferring Offline Hierarchical Ties from Online Social Networks,'' in Workshop on Connecting Online and Offline Life (COOL) (April 8), Seoul, South Korea), WWW (Companion Volume), 2014, pp. 1261-1266.
- M. Xie, L.V.S. Lakshmanan and P.T. Wood, ``IPS: An Interactive Package Configuration System for Trip Planning,'' demo paper in Proc. 39th Int. Conf. on Very Large Data Bases (VLDB) (August 26-30, Trento, Italy), 2013, pp. 1362-1365.
- M. Xie, L.V.S. Lakshmanan and P.T. Wood, ``Efficient Top-k Query Answering using Cached Views,'' in Proc. 16th Int. Conf. on Extending Database Technology (EDBT) (March 18-22, Genoa, Italy), 2013, pp. 489-500.
- P. Barceló, L. Libkin, A.W. Lin and P.T. Wood, ``Expressive Languages for Path Queries over Graph-Structured Data,'' in ACM Trans. on Database Systems, Vol. 37, No. 4, 2012, Article No. 31.
- M. Xie, L.V.S. Lakshmanan and P.T. Wood, ``Composite Recommendations: From Items to Packages,'' in Frontiers of Computer Science, Vol. 6, No. 3, 2012, pp. 264-277.
- P.T. Wood, ``Query Languages for Graph Databases,'' in SIGMOD RECORD, Vol. 41, No. 1 (March), 2012, pp. 50-60.
- A. Poulovassilis, P. Selmer and P.T. Wood, ``Flexible Querying of Lifelong Learner Metadata,'' in IEEE Trans. on Learning Technologies, Vol. 5, No. 2, 2012, pp. 117-129.
- M. Montazerian and P.T. Wood, ``Chasing One's Tail: XPath Containment Under Cyclic DTDs,'' in Proc. 13th International Symposium on Database Programming Languages (August 29, Seattle, Washington), 2011.
- M. Xie, L.V.S. Lakshmanan and P.T. Wood, ``Efficient Rank Join with Aggregation Constraints,'' in Proc. 37th Int. Conf. on Very Large Data Bases (Aug. 29-Sept. 3, Seattle, Washington), PVLDB, Vol. 4, No. 11, 2011, pp. 1201-1212.
- M. San Martín, C. Gutierrez and P.T. Wood, ``SNQL: A Social Network Query and Transformation Language,'' in Proc. 5th Alberto Mendelzon Workshop on Foundations of Data Management (May 9-12, Santiago, Chile), 2011.
- M. Xie, L.V.S. Lakshmanan and P.T. Wood, ``CompRec-Trip: a Composite Recommendation System for Travel Planning,'' demo paper in Proc. 27th IEEE Int. Conf. on Data Engineering (Hannover, Germany, Apr. 11-16), 2011, pp. 1352-1355.
- G. Papamarkos, A. Poulovassilis and P.T. Wood, ``Performance Modelling of Event-Condition-Action Rules in P2P networks,'' in Journal of Computer and System Sciences, DOI: doi:10.1016/j.jcss.2010.02.004, Vol. 77, Elsevier, 2011, pp. 621-636.
- A. Poulovassilis and P.T. Wood, ``Combining Approximation and Relaxation in Semantic Web Path Queries,'' in Proc. 9th International Semantic Web Conference (Shanghai, China, Nov. 7-11), 2010, pp. 631-646.
- M. Xie, L.V.S. Lakshmanan and P.T. Wood, ``Breaking out of the Box of Recommendations: From Items to Packages,'' in Proc. 4th ACM Conf. on Recommender Systems (Barcelona, Spain, Sept. 26-30), 2010, pp. 151-158.
- P. Barceló, C.A. Hurtado, L. Libkin and P.T. Wood, ``Expressive Languages for Path Queries over Graph-Structured Data,'' in Proc. 29th ACM Symposium on Principles of Database Systems (Indianapolis, Indiana, June 6-10), 2010, pp. 3-14.
- P.T. Wood, ``Graph Database,'' in Encyclopedia of Database Systems, Editors-in-chief: M. Tamer Ozsu and Ling Liu, Springer, 2009, pp. 1263-1266.
- C.A. Hurtado, A. Poulovassilis and P.T. Wood, ``Finding Top-k Approximate Answers to Path Queries,'' to appear in Proc. 8th Int. Conf. on Flexible Query Answering Systems (Roskilde, Denmark, Oct. 26-28), 2009.
- C.A. Hurtado, A. Poulovassilis and P.T. Wood, ``Ranking Approximate Answers to Semantic Web Queries,'' in Proc. 6th European Semantic Web Conference (Heraklion, Crete, May 31-June 4), LNCS 5554, Springer-Verlag, 2009, pp. 263-277.
- K. Keenoy, V. Christophides, G. Papamarkos, A. Poulovassilis, D. Kotzinos, P. Rigaux, N. Spyratos, and P.T. Wood, ``Personalisation Services for Self e-Learning Networks,'' in The Learning Grid Handbook: Concepts, Technologies and Applications, S. Salerno, M. Gaeta, P. Ritrovato, N. Capuano, F. Orciouli, S. Miranda and A. Pierri (Editors), IOS Press, February 2008.
- C.A. Hurtado, A. Poulovassilis and P.T. Wood, ``Query Relaxation in RDF,'' Journal on Data Semantics X, LNCS 4900, Springer-Verlag, 2008, pp. 31-61.
- M. Montazerian, P.T. Wood and S.R. Mousavi, ``XPath Query Satisfiability is in PTIME for Real-World DTDs,'' in Proc. Fifth Int. XML Database Symposium (Vienna, Austria, Sept. 23-24), LNCS 4704, Springer-Verlag, 2007, pp. 17-30.
- C.A. Hurtado, A. Poulovassilis and P.T. Wood, ``A Relaxed Approach to RDF Querying,'' in Proc. 5th Int. Semantic Web Conference (Athens, Georgia, Nov. 5-9), LNCS 4273, Springer-Verlag, 2006, pp. 314-328.
- W. Ng, W.-Y. Lam, P.T. Wood and M. Levene, ``XCQ: A Queriable XML Compression System,'' in Knowledge and Information Systems, Vol. 10, No. 4 (November), Springer-Verlag, 2006, pp. 421-452.
- G. Papamarkos, A. Poulovassilis and P.T. Wood, ``Event-Condition-Action Rules on RDF Metadata in P2P Environments,'' in Computer Networks, 50, 10 (July), Elsevier, 2006, pp. 1513-1532.
- A. Poulovassilis, G. Papamarkos and P.T. Wood, ``Event-Condition-Action Rule Languages for the Semantic Web,'' in EDBT Workshops, Reactivity on the Web (Munich, Germany, Mar. 26-31), LNCS 4254, Springer-Verlag, 2006, pp. 855-864.
Recent programme committee membership
Teaching
- Advances in Data Management (an MSc module)
- Internet and Web Technologies (an MSc module)
Short biography
I obtained my BSc and MSc in Computer Science from the University of Cape Town (UCT). I then worked for the Institute for Applied Computer Science at the University of Stellenbosch for 18 months, before leaving for the University of Toronto where I obtained a PhD in Computer Science in 1989. I subsequently spent 9 years as a member of the Department of Computer Science at UCT, before joining the Department of Computer Science at King's College London in 1998. I moved to the School of Computer Science and Information Systems (now Department) at Birkbeck in 2001. I was Head of School from September 2006 until July 2009.