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Characterizing Knowledge on the Semantic Web with Watson
"... Abstract. Watson is a gateway to the Semantic Web: it collects, analyzes and gives access to ontologies and semantic data available online with the objective of supporting their dynamic exploitation by semantic applications. We report on the analysis of 25 500 ontologies and semantic documents colle ..."
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Cited by 48 (9 self)
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Abstract. Watson is a gateway to the Semantic Web: it collects, analyzes and gives access to ontologies and semantic data available online with the objective of supporting their dynamic exploitation by semantic applications. We report on the analysis of 25 500 ontologies and semantic documents collected by Watson, giving an account about the way semantic technologies are used to publish knowledge on the Web, about the characteristics of the published knowledge, and about the networked aspects of the Semantic Web. Our main conclusions are 1- that the Semantic Web is characterized by a large number of small, lightweight ontologies and a small number of large-scale, heavyweight ontologies, and 2- that important efforts still need to be spent on improving the published ontologies (coverage of different topic domains, connectedness of the semantic data, etc.) and the tools that produce and manipulate them. 1
Scalable Authoritative OWL Reasoning for the Web
, 2009
"... In this paper we discuss the challenges of performing reasoning on large scale RDF datasets from the Web. Using ter-Horst's pD * fragment of OWL as a base, we compose a rule-based framework for application to web data: we argue our decisions using observations of undesirable examples taken dire ..."
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Cited by 45 (14 self)
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In this paper we discuss the challenges of performing reasoning on large scale RDF datasets from the Web. Using ter-Horst's pD * fragment of OWL as a base, we compose a rule-based framework for application to web data: we argue our decisions using observations of undesirable examples taken directly from the Web. We further temper our OWL fragment through consideration of "authoritative sources" which counter-acts an observed behaviour which we term "ontology hijacking": new ontologies published on the Web re-defining the semantics of existing entities resident in other ontologies. We then present our system for performing rule-based forward-chaining reasoning which we call SAOR: Scalable Authoritative OWL Reasoner. Based upon observed characteristics of web data and reasoning in general, we design our system to scale: our system is based upon a separation of terminological data from assertional data and comprises of a lightweight in-memory index, on-disk sorts and file-scans. We evaluate our methods on a dataset in the order of a hundred million statements collected from real-world web sources and present scale-up experiments on a dataset in the order of a billion statements collected from the Web.
SAOR: Authoritative Reasoning for the Web
- In Proceedings of the 3rd Asian Semantic Web Conference (ASWC 2008), Bankok
, 2008
"... Abstract. In this paper we discuss the challenges of performing reasoning on large scale RDF datasets from the Web. We discuss issues and practical solutions relating to reasoning over web data using a rule-based approach to forward-chaining; in particular, we identify the problem of ontology hijack ..."
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Cited by 34 (7 self)
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Abstract. In this paper we discuss the challenges of performing reasoning on large scale RDF datasets from the Web. We discuss issues and practical solutions relating to reasoning over web data using a rule-based approach to forward-chaining; in particular, we identify the problem of ontology hijacking: new ontologies published on the Web re-defining the semantics of existing concepts resident in other ontologies. Our solution introduces consideration of authoritative sources. Our system is designed to scale, comprising of file-scans and selected lightweight on-disk indices. We evaluate our methods on a dataset in the order of a hundred million statements collected from real-world Web sources. 1
WATSON: A Gateway for the Semantic Web
- Poster session of the European Semantic Web Conference, ESWC
, 2007
"... Abstract. As the Semantic Web is gaining momentum, more and more semantic data is available online. The second generation of Semantic Web applications already exploit this phenomenon by relying on this huge amount of semantic content. Looking at the requirements of these applications, we show that t ..."
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Cited by 32 (17 self)
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Abstract. As the Semantic Web is gaining momentum, more and more semantic data is available online. The second generation of Semantic Web applications already exploit this phenomenon by relying on this huge amount of semantic content. Looking at the requirements of these applications, we show that there is a need for an efficient access point to the Semantic Web, designed to take into account the semantic nature of the knowledge available online. However, because they rely on “classical Web ” techniques, existing solutions fail to fulfill this need. In this paper, we describe the design of Watson, a gateway for the Semantic Web, which has been guided by the requirements of Semantic Web applications and by lessons learnt from previous systems. We show how Watson exploits the strengths of semantic technologies to provide fundamental functionalities for a more suitable access to online knowledge. We also report on using these functionalities to analyze some of the characteristics of the content of the Semantic Web.
Ontosearch2: Searching and querying web ontologies
- In Proc. of the IADIS International Conference
, 2006
"... Ontologies are important components of web-based applications. While the Web makes an increasing number of ontologies widely available for applications, how to discover ontologies in the Web becomes a more challenging issue. Existing approaches are mainly based on keywords and metadata information o ..."
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Cited by 32 (13 self)
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Ontologies are important components of web-based applications. While the Web makes an increasing number of ontologies widely available for applications, how to discover ontologies in the Web becomes a more challenging issue. Existing approaches are mainly based on keywords and metadata information of ontologies, rather than semantic entailments of ontologies. In this paper, we present a Semantic Web engine, called ONTOSEARCH2, which searches and queries Web ontologies by creating and storing a copy of ontologies in a tractable description logic. ONTOSEARCH2 allows formal querying of its repository, including both the structures and instances of ontologies, using the SPARQL query language. Furthermore, this paper reports on preliminary, but encouraging, benchmark results which compare ONTOSEARCH2’s response times on a number of queries with those of existing knowledge base management systems.
An empirical survey of Linked Data conformance
, 2009
"... There has been a recent, tangible growth in RDF published on the Web in accordance with the Linked Data principles and best practices, the result of which has been dubbed the “Web of Data”. Linked Data guidelines are designed to facilitate ad hoc re-use and integration of conformant structured data— ..."
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Cited by 31 (3 self)
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There has been a recent, tangible growth in RDF published on the Web in accordance with the Linked Data principles and best practices, the result of which has been dubbed the “Web of Data”. Linked Data guidelines are designed to facilitate ad hoc re-use and integration of conformant structured data—across the Web—by consumer applications; however, thus far, systems have yet to emerge that convincingly demonstrate the potential applications for consuming currently available Linked Data. Herein, we compile a list of fourteen concrete guidelines as given in the “How to Publish Linked Data on the Web ” tutorial. Thereafter, we evaluate conformance of current RDF data providers with respect to these guidelines. Our evaluation is based on quantitative empirical analyses of a crawl of ∼4 million RDF/XML documents constituting over 1 billion quadruples, where we also look at the stability of hosted documents for a corpus consisting of nine monthly snapshots from a sample of 151 thousand documents. Backed by our empirical survey, we provide insights into the current level of conformance with respect to various Linked Data guidelines, enumerating lists of the most (non-)conformant data providers. We show that certain guidelines are broadly adhered to (esp. use HTTP URIs, keep URIs stable), whilst others are commonly overlooked (esp. provide licencing and human-readable meta-data). We also compare PageRank scores for the data-providers and their conformance to Linked Data guidelines, showing that both factors negatively correlate for guidelines restricting use of RDF features, while positively correlating for guidelines encouraging external linkage and vocabulary re-use. Finally, we present a summary of conformance for the different guidelines, and present the top-ranked data providers in terms of a combined PageRank and Linked Data conformance score.
Evaluating the semantic web: A task-based approach
- of Lecture Notes in Computer Science
, 2007
"... Abstract. The increased availability of online knowledge has led to the design of several algorithms that solve a variety of tasks by harvesting the Semantic Web, i.e., by dynamically selecting and exploring a mul-titude of online ontologies. Our hypothesis is that the performance of such novel algo ..."
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Cited by 26 (12 self)
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Abstract. The increased availability of online knowledge has led to the design of several algorithms that solve a variety of tasks by harvesting the Semantic Web, i.e., by dynamically selecting and exploring a mul-titude of online ontologies. Our hypothesis is that the performance of such novel algorithms implicitly provides an insight into the quality of the used ontologies and thus opens the way to a task-based evaluation of the Semantic Web. We have investigated this hypothesis by studying the lessons learnt about online ontologies when used to solve three tasks: ontology matching, folksonomy enrichment, and word sense disambigua-tion. Our analysis leads to a suit of conclusions about the status of the Semantic Web, which highlight a number of strengths and weaknesses of the semantic information available online and complement the findings of other analysis of the Semantic Web landscape. 1
Benchmarking OWL Reasoners
"... Abstract. The growing popularity of semantic applications makes scalability of ontology reasoning tasks increasingly important. In this work, we first analyze the ontology landscape on the web, and identify typical clusters of expressivity. Second, we benchmark current ontology reasoners, by using r ..."
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Cited by 23 (1 self)
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Abstract. The growing popularity of semantic applications makes scalability of ontology reasoning tasks increasingly important. In this work, we first analyze the ontology landscape on the web, and identify typical clusters of expressivity. Second, we benchmark current ontology reasoners, by using representative ontologies for each cluster and a comprehensive set of queries. We point out applicability of specific reasoners to certain expressivity clusters and reasoning tasks. 1
Exploiting RDFS and OWL for Integrating Heterogeneous, Large-Scale, Linked Data Corpora
, 2011
"... The Web contains a vast amount of information on an abundance of topics, much of which is encoded as structured data indexed by local databases. However, these databases are rarely interconnected and information reuse across sites is limited. Semantic Web standards offer a possible solution in the ..."
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Cited by 17 (11 self)
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The Web contains a vast amount of information on an abundance of topics, much of which is encoded as structured data indexed by local databases. However, these databases are rarely interconnected and information reuse across sites is limited. Semantic Web standards offer a possible solution in the form of an agreed-upon data model and set of syntaxes, as well as metalanguages for publishing schema-level information, offering a highly-interoperable means of publishing and interlinking structured data on the Web. Thanks to the Linked Data community, an unprecedented lode of such data has now been published on the Web—by individuals, academia, communities, corporations and governmental organisations alike—on a medley of often overlapping topics. This new publishing paradigm has opened up a range of new and interesting research topics with respect to how this emergent “Web of Data” can be harnessed and exploited by consumers. Indeed, although Semantic
Semantic Web Service Selection with SAWSDL-MX
"... Abstract. In this paper, we present an approach to hybrid semantic Web service selection of semantic services in SAWSDL based on logicbased matching as well as text retrieval strategies. We discuss the principles of semantic Web service description in SAWSDL and selected problems for service matchin ..."
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Cited by 15 (0 self)
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Abstract. In this paper, we present an approach to hybrid semantic Web service selection of semantic services in SAWSDL based on logicbased matching as well as text retrieval strategies. We discuss the principles of semantic Web service description in SAWSDL and selected problems for service matching implied by its specification. Based on the result of this discussion, we present different variants of hybrid semantic selection of SAWSDL services implemented by our matchmaker called SAWSDL-MX together with preliminary results of its performance in terms of recall/precision and average query response time. For experimental evaluation we created a first version of a SAWSDL service retrieval test collection called SAWSDL-TC. 1
