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Displaying 1-13 out of 13 total
On Computing Deltas of RDF/S Knowledge Bases
Found in: ACM Transactions on the Web (TWEB)
By Dimitris Zeginis, Vassilis Christophides, Vassilis Christophides, Yannis Tzitzikas, Yannis Tzitzikas
Issue Date:July 2011
pp. 1-36
The ability to compute the differences that exist between two RDF/S Knowledge Bases (KB) is an important step to cope with the evolving nature of the Semantic Web (SW). In particular, RDF/S deltas can be employed to reduce the amount of data that need to b...
On Provenance of Queries on Semantic Web Data
Found in: IEEE Internet Computing
By Yannis Theoharis, Irini Fundulaki, Grigoris Karvounarakis, Vassilis Christophides
Issue Date:January 2011
pp. 31-39
Capturing trustworthiness, reputation, and reliability of Semantic Web data manipulated by SPARQL requires researchers to represent adequate provenance information, usually modeled as source data annotations and propagated to query results along with a que...
Efficient Rewriting Algorithms for Preference Queries
Found in: Data Engineering, International Conference on
By Periklis Georgiadis, Ioannis Kapantaidakis, Vassilis Christophides, Elhadji Mamadou Nguer, Nicolas Spyratos
Issue Date:April 2008
pp. 1101-1110
Preference queries are crucial for various applications (e.g. digital libraries) as they allow users to discover and order data of interest in a personalized way. In this paper, we define preferences as preorders over relational attributes and their respec...
On Graph Features of Semantic Web Schemas
Found in: IEEE Transactions on Knowledge and Data Engineering
By Yannis Theoharis, Yannis Tzitzikas, Dimitris Kotzinos, Vassilis Christophides
Issue Date:May 2008
pp. 692-702
In this paper, we measure and analyze the graph features of Semantic Web (SW) schemas with focus on power-law degree distributions. Our main finding is that the majority of SW schemas with a significant number of properties (resp. classes) approximate a po...
Algebraic structures for capturing the provenance of SPARQL queries
Found in: Proceedings of the 16th International Conference on Database Theory (ICDT '13)
By Floris Geerts, Grigoris Karvounarakis, Irini Fundulaki, Vassilis Christophides
Issue Date:March 2013
pp. 153-164
We show that the evaluation of SPARQL algebra queries on various notions of annotated RDF graphs can be seen as particular cases of the evaluation of these queries on RDF graphs annotated with elements of so-called spm-semirings. Spm-semirings extend semir...
Processing continuous text queries featuring non-homogeneous scoring functions
Found in: Proceedings of the 21st ACM international conference on Information and knowledge management (CIKM '12)
By Bernd Amann, Nelly Vouzoukidou, Vassilis Christophides
Issue Date:October 2012
pp. 1065-1074
In this work we are interested in the scalable processing of content filtering queries over text item streams. In particular, we are aiming to generalize state of the art solutions with non-homogeneous scoring functions combining query-independent item imp...
Diachronic linked data: towards long-term preservation of structured interrelated information
Found in: Proceedings of the First International Workshop on Open Data (WOD '12)
By Dimitris Kotzinos, Dimitris Sacharidis, François Bancilhon, George Papastefanatos, Giorgos Flouris, Helen Parkinson, Kostas Thiveos, Peter Buneman, Sören Auer, Theodore Dalamagas, Vassilis Christophides, Yannis Stavrakas
Issue Date:May 2012
pp. 31-39
The Linked Data Paradigm is a promising technology for publishing, sharing, and connecting data on the Web, which provides new perspectives for data integration and interoperability. However, the proliferation of distributed, interconnected linked data sou...
Online curriculum on the semantic Web: the CSD-UoC portal for peer-to-peer e-learning
Found in: Proceedings of the 14th international conference on World Wide Web (WWW '05)
By Apostolos Apostolidis, Dimitris Kotzinos, Nikolaos Athanasis, Sofia Pediaditaki, Vassilis Christophides
Issue Date:May 2005
pp. 307-314
Online Curriculum Portals aim to support networks of instructors and learners by providing a space of convergence for enhancing peer-to-peer learning interactions among individuals of an educational institution. To this end, effective, open and scalable e-...
E-services: a look behind the curtain
Found in: Proceedings of the twenty-second ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems (PODS '03)
By Jianwen Su, Michael Benedikt, Richard Hull, Vassilis Christophides
Issue Date:June 2003
pp. 1-14
The emerging paradigm of electronic services promises to bring to distributed computation and services the flexibility that the web has brought to the sharing of documents. An understanding of fundamental properties of e-service composition is required in ...
On labeling schemes for the semantic web
Found in: Proceedings of the twelfth international conference on World Wide Web (WWW '03)
By Dimitris Plexousakis, Michel Scholl, Sotirios Tourtounis, Vassilis Christophides
Issue Date:May 2003
pp. 544-555
This paper focuses on the optimization of the navigation through voluminous subsumption hierarchies of topics employed by Portal Catalogs like Netscape Open Directory (ODP). We advocate for the use of labeling schemes for modeling these hierarchies in orde...
RQL: a declarative query language for RDF
Found in: Proceedings of the eleventh international conference on World Wide Web (WWW '02)
By Dimitris Plexousakis, Gregory Karvounarakis, Michel Scholl, Sofia Alexaki, Vassilis Christophides
Issue Date:May 2002
pp. 592-603
Real-scale Semantic Web applications, such as Knowledge Portals and E-Marketplaces, require the management of large volumes of metadata, i.e., information describing the available Web content and services. Better knowledge about their meaning, usage, acces...
Conference review: Semantic Web Workshop:: models, architectures and management
Found in: intelligence
By Dimitris Plexousakis, Panos Constantpoulos, Vassilis Christophides
Issue Date:March 1999
pp. 39-44
This article is a survey of research areas in which motion plays a pivotal role. The aim of the article is to review current approaches to modeling motion together with related data structures and algorithms, and to summarize the challenges that lie ahead ...
Evaluating queries with generalized path expressions
Found in: Proceedings of the 1996 ACM SIGMOD international conference on Management of data (SIGMOD '96)
By Guido Moerkotte, Sophie Cluet, Vassilis Christophides
Issue Date:June 1996
pp. 219-230
In the past few years, query languages featuring generalized path expressions have been proposed. These languages allow the interrogation of both data and structure. They are powerful and essential for a number of applications. However, until now, their ev...